*******************************************************************************
* *
* Crafty, copyright 1996-2010 by Robert M. Hyatt, Ph.D., Associate Professor *
* of Computer and Information Sciences, University of Alabama at Birmingham. *
* *
* Crafty is a team project consisting of the following members. These are *
* the people involved in the continuing development of this program, there *
* are no particular members responsible for any specific aspect of Crafty. *
* *
* Michael Byrne, Pen Argyle, PA. *
* Robert Hyatt, University of Alabama at Birmingham. *
* Tracy Riegle, Hershey, PA. *
* Peter Skinner, Edmonton, AB Canada. *
* Ted Langreck . *
* *
* All rights reserved. No part of this program may be reproduced in any *
* form or by any means, for other than your personal use, without the *
* express written permission of the authors. This program may not be used *
* in whole, nor in part, to enter any computer chess competition without *
* written permission from the authors. Such permission will include the *
* requirement that the program be entered under the name "Crafty" so that *
* the program's ancestry will be known. *
* *
* Copies of the source must contain the original copyright notice intact. *
* *
* Any changes made to this software must also be made public to comply with *
* the original intent of this software distribution project. These *
* restrictions apply whether the distribution is being done for free or as *
* part or all of a commercial product. The authors retain sole ownership *
* and copyright on this program except for 'personal use' explained below. *
* *
* Personal use includes any use you make of the program yourself, either by *
* playing games with it yourself, or allowing others to play it on your *
* machine, and requires that if others use the program, it must be clearly *
* identified as "Crafty" to anyone playing it (on a chess server as one *
* example). Personal use does not allow anyone to enter this into a chess *
* tournament where other program authors are invited to participate. IE you *
* can do your own local tournament, with Crafty + other programs, since this *
* is for your personal enjoyment. But you may not enter Crafty into an *
* event where it will be in competition with other programs/programmers *
* without permission as stated previously. *
* *
* Crafty is the "son" (direct descendent) of Cray Blitz. it is designed *
* totally around the bit-board data structure for reasons of speed of ex- *
* ecution, ease of adding new knowledge, and a *significantly* cleaner *
* overall design. it is written totally in ANSI C with some few UNIX system *
* calls required for I/O, etc. *
* *
* main() is the driver for the chess program. Its primary function is to *
* cycle between asking the user for a move and calling for a tree search *
* to produce a move for the program. After accepting an input string from *
* the user, this string is first passed to Option() which checks to see if *
* it is a command to the program. If Option() returns a non-zero result, *
* the input was a command and was executed, otherwise the input should be *
* passed to input() for conversion to the internal move format. *
* *
* The following diagram shows how bit numbers / squares match up in Crafty's *
* bitboard arrays. Note that bit zero (LSB) corresponds to square A, which *
* makes this a mental challenge to take a 64 bit value and visualize it as *
* chess board, since the files are reversed. This was done for the *
* following reasons: (1) bit 0 needs to be the LSB, and bit 63 needs to be *
* the MSB so that the Intel BSF/BSR instructions return the proper square *
* number without any remapping. (2) the lower 3 bits (file number) are now *
* 0 for A, 1 for B, ..., 7 for H. The upper 3 bits (rank number) are then *
* 0 for rank 1, 1 for rank 2, ..., 7 for rank 8. *
* *
* A8 B8 C8 D8 E8 F8 G8 H8 *
* A7 B7 C7 D7 E7 F7 G7 H7 *
* A6 B6 C6 D6 E6 F6 G6 H6 *
* A5 B5 C5 D5 E5 F5 G5 H5 *
* A4 B4 C4 D4 E4 F4 G4 H4 *
* A3 B3 C3 D3 E3 F3 G3 H3 *
* A2 B2 C2 D2 E2 F2 G2 H2 *
* A1 B1 C1 D1 E1 F1 G1 H1 *
* *
* 56 57 58 59 60 61 62 63 *
* 48 49 50 51 52 53 54 55 *
* 40 41 42 43 44 45 46 47 *
* 32 33 34 35 36 37 38 39 *
* 24 25 26 27 28 29 30 31 *
* 16 17 18 19 20 21 22 23 *
* 8 9 10 11 12 13 14 15 *
* 0 1 2 3 4 5 6 7 *
* *
* version description *
* *
* 1.0 First version of the bit-board program to play a legitimate game *
* even though significant features are missing: transposition *
* table, sophisticated scoring, etc. *
* *
* 1.1 Added the minimal window search. At each ply in the tree, the *
* first branch is searched with the normal alpha/beta window, while *
* remaining nodes are searched with value/value+1 which was *
* returned from searching the first branch. If such a search *
* returns the upper bound, this position is once again searched *
* with the normal window. *
* *
* 1.2 Added the classic null-move search. The program searches the *
* sub-tree below the null move (typically) one play shallower than *
* the normal search, saving a lot of time. *
* *
* 1.3 Added the transposition table support. This also includes the *
* code in Iterate() necessary to propagate the principal variation *
* from one iteration to the next to improve move ordering. *
* *
* 1.4 Modified the transposition table to use three tables, one for 64 *
* bits of white entry, one for 64 bits of black entry, and one with *
* the remaining 32 bits of white and black entry combined into one *
* 64 bit word. Eliminated the "bit fields" since they seemed to be *
* erratic on most compilers and made portability nearly impossible. *
* *
* 1.5 Pawn scoring added. This required three additions to the code: *
* (1) InitializePawnMasks() which produces the necessary masks to *
* let us efficiently detect isolated, backward, passed, etc. pawns; *
* (2) a pawn hash table to store recently computed pawn scores so *
* it won't be too expensive to do complex analysis; (3) Evaluate() *
* now evaluates pawns if the current pawn position is not in the *
* pawn hash table. *
* *
* 1.6 Piece scoring added, although it is not yet complete. Also, the *
* search now uses the familiar zero-width window search for all but *
* the first move at the root, in order to reduce the size of the *
* tree to a nearly optimal size. This means that a move that is *
* only one point better than the first move will "fail high" and *
* have to be re-searched a second time to get the true value. If *
* the new best move is significantly better, it may have to be *
* searched a third time to increase the window enough to return the *
* score. *
* *
* 1.7 Replaced the old "killer" move ordering heuristic with the newer *
* "history" ordering heuristic. This version uses the 12-bit key *
* formed by <from><to> to index into the history table. *
* *
* 1.8 Added pondering for both PC and UNIX-based machines. Also other *
* improvements include the old Cray Blitz algorithm that takes the *
* P.V. returned by the tree search, and "extends" it by looking up *
* positions in the transposition table, which improves move *
* ordering significantly. Repetitions are now handled correctly. *
* *
* 1.9 Added an opening book with flags to control which moves are *
* selected for play. The book maintenance code is stubbed directly *
* into the program, so that no additional executables are needed. *
* *
* 1.10 Added king safety + hashing (as done in the old Cray Blitz). *
* Nothing novel other than the use of bit-masks to speed up some of *
* the tests. *
* *
* 1.11 Additional evaluation knowledge plus log_file so that program *
* saves a record of the game statistics for later analysis. Added *
* the "annotate" command to make the program analyze a game or part *
* of a game for testing/debugging. *
* *
* 1.12 Added ICS (Internet Chess Server) support for Xboard support so *
* that Crafty can play on ICS in an automated manner. Added new *
* commands to be compatible with Xboard. Crafty also has a new *
* command-line interface that allows options to be entered on the *
* command-line directly, ie: "crafty alarm=off verbose=2" will *
* start the program, set the move alarm off, and set verbose to *
* 2. This allows an "alias" to easily customize the program. *
* *
* 1.13 Added time-control logic to the program. It now monitors how *
* much time both it and its opponent uses when thinking about a *
* move to make. When pondering, it only times itself from the *
* point that a move is actually entered. *
* *
* 1.14 Added the piece/square tables to the program to move static *
* scoring to the root of the tree since it never changes (things *
* like centralization of pieces, etc.) also some minor tuning of *
* numbers to bring positional score "swings" down some. *
* *
* 1.15 Added edit so that positions can be altered (and so ICS games *
* can be resumed after they are adjourned). Also added a "force" *
* command to force the program to play a different move than the *
* search selected. Search timing allocation slightly altered to *
* improve ICS performance. *
* *
* 1.16 Significant adjustments to evaluation weights to bring positional *
* scores down to below a pawn for "normal" positions. Some small *
* "tweaks" to king safety as well to keep the king safer. *
* *
* 1.17 Added "development" evaluation routine to encourage development *
* and castling before starting on any tactical "sorties." Also *
* repaired many "bugs" in evaluation routines. *
* *
* 1.18 Added the famous Cray Blitz "square of the king" passed pawn *
* evaluation routine. This will evaluate positions where one *
* side has passed pawns and the other side has no pieces, to see *
* if the pawn can outrun the defending king and promote. Note that *
* this is ridiculously fast because it only requires one AND *
* to declare that a pawn can't be caught! *
* *
* 2.0 initial version preparing for search extension additions. This *
* version has a new "next_evasion()" routine that is called when *
* the king is in check. It generates sensible (nearly all are *
* legal) moves which include capturing the checking piece (if there *
* is only one), moving the king (but not along the checking ray), *
* and interpositions that block the checking ray (if there is only *
* one checking piece. *
* *
* 2.1 Search is now broken down into three cleanly-defined phases: *
* (1) basic full-width search [Search()]; (2) extended tactical *
* search [extend()] which includes winning/even captures and then *
* passed pawn pushes to the 6th or 7th rank (if the pawn pushes *
* are safe); (3) normal quiescence search [Quiesce()] which only *
* includes captures that appear to gain material. *
* *
* 2.2 King safety code re-written and cleaned up. Crafty was giving *
* multiple penalties which was causing the king safety score to be *
* extremely large (and unstable.) Now, if it finds something wrong *
* with king safety, it only penalizes a weakness once. *
* *
* 2.3 King safety code modified further, penalties were significant *
* enough to cause search anomolies. Modified rook scoring to avoid *
* having the rook trapped in the corner when the king is forced to *
* move rather than castle, and to keep the rook in a position to be *
* able to reach open files in one move, which avoids getting them *
* into awkward positions where they become almost worthless. *
* *
* 2.4 King safety code completely rewritten. It now analyzes "defects" *
* in the king safety field and counts them as appropriate. These *
* defects are then summed up and used as an index into a vector of *
* of values that turns them into a score in a non-linear fashion. *
* Increasing defects quickly "ramp up" the score to about 1/3+ of *
* a pawn, then additional faults slowly increase the penalty. *
* *
* 2.5 First check extensions added. In the extension search (stage *
* between full-width and captures-only, up to two checking moves *
* can be included, if there are checks in the full-width part of *
* the search. If only one check occurs in the full-width, then *
* only one check will be included in the extension phase of the *
* selective search. *
* *
* 2.6 Evaluation modifications attempting to cure Crafty's frantic *
* effort to develop all its pieces without giving a lot of regard *
* to the resulting position until after the pieces are out. *
* *
* 2.7 New evaluation code to handle the "outside passed pawn" concept. *
* Crafty now understands that a passed pawn on the side away from *
* the rest of the pawns is a winning advantage due to decoying the *
* king away from the pawns to prevent the passer from promoting. *
* The advantage increases as material is removed from the board. *
* *
* 3.0 The 3.* series of versions will primarily be performance en- *
* hancements. The first version (3.0) has a highly modified *
* version of MakeMove() that tries to do no unnecessary work. It *
* is about 25% faster than old version of MakeMove() which makes *
* Crafty roughly 10% faster. Also calls to Mask() have been *
* replaced by constants (which are replaced by calls to Mask() on *
* the Crays for speed) to eliminate function calls. *
* *
* 3.1 Significantly modified king safety again, to better detect and *
* react to king-side attacks. Crafty now uses the recursive null- *
* move search to depth-2 instead of depth-1, which results in *
* slightly improved speed. *
* *
* 3.2 Null-move restored to depth-1. Depth-2 proved unsafe as Crafty *
* was overlooking tactical moves, particularly against itself, *
* which lost several "won" games. *
* *
* 3.3 Additional king-safety work. Crafty now uses the king-safety *
* evaluation routines to compare king safety for both sides. If *
* one side is "in distress" pieces are attracted to that king in *
* "big hurry" to either attack or defend. *
* *
* 3.4 "Threat extensions" added. Simply, this is a null-move search *
* used to determine if a move is good only because it is a horizon *
* effect type move. we do a null move search after a move fails *
* high anywhere in the tree. The window is normally lowered by 1.5 *
* pawns, the idea being that if the fail-high move happens in a *
* position that fails "really low" with a null move, then this move *
* might be a horizon move. To test this, re-search this move with *
* the depth increased by one. *
* *
* 3.5 50-move rule implemented. A count of moves since the last pawn *
* move or capture is kept as part of the position[] structure. It *
* is updated by MakeMove(). When this number reaches 100 (which *
* in plies is 50 moves) RepetitionCheck() will return the draw *
* score immediately, just as though the position was a repetition *
* draw. *
* *
* 3.6 Search extensions cleaned up to avoid excessive extensions which *
* produced some wild variations, but which was also slowing things *
* down excessively. *
* *
* 3.7 Endgame strategy added. Two specifics: KBN vs K has a piece/sq *
* table that will drive the losing king to the correct corner. For *
* positions with no pawns, scoring is altered to drive the losing *
* king to the edge and corner for mating purposes. *
* *
* 3.8 Hashing strategy modified. Crafty now stores search value or *
* bound, *and* positional evaluation in the transposition table. *
* This avoids about 10-15% of the "long" evaluations during the *
* middlegame, and avoids >75% of them in endgames. *
* *
* 4.0 Evaluation units changed to "millipawns" where a pawn is now *
* 1000 rather than the prior 100 units. This provides more *
* "resolution" in the evaluation and will let Crafty have large *
* positional bonuses for significant things, without having the *
* small positional advantages add up and cause problems. V3.8 *
* exhibited a propensity to "sac the exchange" frequently because *
* of this. It is hoped that this is a thing of the past now. *
* Also, the "one legal reply to check" algorithm is now being used. *
* In short, if one side has only one legal reply to a checking move *
* then the other side is free to check again on the next ply. this *
* only applies in the "extension" search, and allows some checks *
* that extend() would normally not follow. *
* *
* 4.1 Extension search modified. It now "tracks" the basic iteration *
* search depth up to some user-set limit (default=6). For shallow *
* depths, this speeds things up, while at deeper depths it lets the *
* program analyze forcing moves somewhat deeper. *
* *
* 4.2 Extension search modified. Fixed a problem where successive *
* passed-pawn pushes were not extended correctly by extend() code. *
* Threat-extension margin was wrong after changing the value of a *
* pawn to 1000, it is now back to 1.5 pawns. *
* *
* 4.3 Hash scoring "repaired." As the piece/square tables changed, the *
* transposition table (positional evaluation component) along with *
* the pawn and king-safety hash tables prevented the changes from *
* affecting the score, since the hashed scores were based on the *
* old piece/square table values. Now, when any piece/square table *
* is modified, the affected hash tables are cleared of evaluation *
* information. *
* *
* 4.4 Piece/square tables simplified, king tropism scoring moved to *
* Evaluate() where it is computed dynamically now as it should be. *
* *
* 4.5 Book move selection algorithm replaced. Crafty now counts the *
* number of times each book move was played as the book file is *
* created. Since these moves come (typically) from GM games, the *
* more frequently a move appears, the more likely it is to lead to *
* a sound position. Crafty then enumerates all possible book moves *
* for the current position, computes a probability distribution for *
* each move so that Crafty will select a move proportional to the *
* number of times it was played in GM games (for example, if e4 was *
* played 55% of the time, then Crafty will play e4 55% of the time) *
* although the special case of moves played too infrequently is *
* handled by letting the operator set a minimum threshold (say 5) *
* Crafty won't play moves that are not popular (or are outright *
* blunders as the case may be.) Pushing a passed pawn to the 7th *
* rank in the basic search [Search() module] now extends the search *
* by two plies unless we have extended this ply already (usually a *
* check evasion) or unless we have extended the whole line to more *
* than twice the nominal iteration depth. *
* *
* 5.0 Selective search extensions removed. With the extensions now in *
* the basic full-width search, these became more a waste of time *
* than anything useful, and removing them simplifies things quite *
* a bit. *
* *
* 5.1 Pondering logic now has a "puzzling" feature that is used when *
* the search has no move to ponder. It does a short search to find *
* a move and then ponders that move, permanently eliminating the *
* "idle" time when it has nothing to ponder. *
* *
* 5.2 Evaluation terms scaled down to prevent positional scores from *
* reaching the point that sacrificing material to avoid simple *
* positional difficulties begins to look attractive. *
* *
* 5.3 Performance improvement produced by avoiding calls to MakeMove() *
* when the attack information is not needed. Since the first test *
* done in Quiesce() is to see if the material score is so bad that *
* a normal evaluation and/or further search is futile, this test *
* has been moved to inside the loop *before* Quiesce() is *
* recursively called, avoiding the MakeMove() work only to *
* discover that the resulting position won't be searched further. *
* *
* 5.4 New Swap() function that now understands indirect attacks through *
* the primary attacking piece(s). This corrects a lot of sloppy *
* move ordering as well as make the "futility" cutoffs added in *
* in version 5.3 much more reliable. *
* *
* 5.5 Checks are now back in the quiescence search. Crafty now stores *
* a negative "draft" in the transposition table rather than forcing *
* any depth < 0 to be zero. The null-move search now searches the *
* null-move to depth-1 (R=1) rather than depth-2 (R=2) which seemed *
* to cause some tactical oversights in the search. *
* *
* 5.6 Improved move ordering by using the old "killer move" idea. An *
* additional advantage is that the killers can be tried before *
* generating any moves (after the captures.) Quiescence now only *
* includes "safe" checks (using Swap() to determine if it is a safe *
* checking move. *
* *
* 5.7 King safety now "hates" a pawn at b3/g3 (white) or b6/g6 (black) *
* to try and avoid the resulting mate threats. *
* *
* 5.8 EvaluateOutsidePassedPawns() fixed to correctly evaluate those *
* positions where both sides have outside passed pawns. Before *
* this fix, it only evaluated positions where one side had a passed *
* pawn, which overlooked those won/lost positions where both sides *
* have passed pawns but one is "distant" or "outside" the other. *
* *
* 5.9 Removed "futility" forward pruning. Exhaustive testing has *
* proved that this causes significant tactical oversights. *
* *
* 5.10 Added code to handle king and pawn vs king, which understands *
* the cases where the pawn can't outrun the king, but has to be *
* assisted along by the king. *
* *
* 5.11 Two king-safety changes. (1) The program's king safety score is *
* now "doubled" to make it much less likely that it will try to win *
* a pawn but destroy it's king-side. (2) The attack threshold has *
* been lowered which is used to key the program that it is now *
* necessary to move pieces to defend the king-side, in an effort to *
* protect a king-side that is deemed somewhat unsafe. *
* *
* 5.12 Improved null-move code by computing the Knuth/Moore node type *
* and then only trying null-moves at type 2 nodes. This has *
* resulted in a 2x speedup in test positions. *
* *
* 5.13 Optimization to avoid doing a call to MakeMove() if it can be *
* avoided by noting that the move is not good enough to bring the *
* score up to an acceptable level. *
* *
* 5.14 Artificially isolated pawns recognized now, so that Crafty won't *
* push a pawn so far it can't be defended. Also, the bonus for a *
* outside passed pawn was nearly doubled. *
* *
* 5.15 Passed pawns supported by a king, or connected passed pawns now *
* get a large bonus as they advance. Minor fix to the ICC resume *
* feature to try to avoid losing games on time. *
* *
* 6.0 Converted to rotated bitboards to make attack generation *much* *
* faster. MakeMove() now can look up the attack bit vectors *
* rather than computing them which is significantly faster. *
* *
* 6.1 Added a "hung piece" term to Evaluate() which penalizes the side *
* to move if a piece is attacked by a lesser piece, or a piece is *
* attacked and not defended at all. Additionally, a new scoring *
* term was added to detect a weak back rank (where the king does *
* not attack an empty square on the 2nd rank, and there are no *
* horizontally sliding pieces [rook or queen] on the first rank to *
* guard against back-rank mates. *
* *
* 6.2 Modified the "futility" cutoff to (a) emulate the way the program *
* normally searches, but avoiding MakeMove() calls when possible, *
* and (2) not searching a move near the horizon if the material *
* score is hopeless. *
* *
* 6.3 Null-move code moved from NextMove() directly into Search(). *
* this results is a "cleaner" implementation, as well as fixing an *
* error in the node type, caused by Search() thinking that after *
* the first move tried fails to cause a cutoff, that suddenly this *
* node is a type=3 node (Knuth and Moore). This bug would then *
* introduce null-moves into later nodes that are a waste of time. *
* *
* 6.4 Pawn scoring modified. Passed pawns were scored low enough that *
* Crafty would let the opponent create one in the endgame (as long *
* as it wasn't an "outside" passed pawn). This required adjusting *
* isolated pawns as well. All "weak" pawns (pawns on open files *
* that aren't defended by a pawn) are not penalized so much if *
* there aren't any rooks/queens to attack on the file. *
* *
* 7.0 Removed the to.attack and from.attack bitboards. These are now *
* computed as needed, using the rotated bitboards. Hung piece *
* stuff removed due to lack of any verified benefit. *
* *
* 7.1 Modified next.c and nextc.c so that they check "mvv_lva_ordering" *
* to determine which capture ordering strategy to use. Note that *
* setting this to "1" (default at present) disables the forward *
* pruning in quiescence search that wants to cull losing captures. *
* *
* 7.2 Major clean-up of MakeMove() using macros to make it easier to *
* read and understand. Ditto for other modules as well. Fixed a *
* bug in Evaluate() where bishop scoring failed in endgame *
* situations, and discouraged king centralization. *
* *
* 7.3 Evaluate() is no longer called if material is too far outside the *
* current alpha/beta window. The time-consuming part of Evaluate() *
* is no longer done if the major scoring contributors in Evaluate() *
* haven't pulled the score within the alpha/beta window, and the *
* remainder of Evaluate() can't possible accomplish this either. *
* Gross error in EvaluatePawns() fixed, which would "forget" all *
* of the pawn scoring done up to the point where doubled white *
* pawns were found. error was xx=+ rather than xx+=, which had *
* an extremely harmful effect on pawn structure evaluation. *
* *
* 7.4 Performance improvements produced by elimination of bit-fields. *
* This was accomplished by hand-coding the necessary ANDs, ORs, and *
* SHIFTs necessary to accomplish the same thing, only faster. *
* *
* 7.5 Repetition code modified. It could store at replist[-1] which *
* clobbered the long long word just in front of this array. *
* *
* 7.6 Null move search now searches with R=2, unless within 3 plies *
* of the quiescence search, then it searches nulls with R=1. *
* *
* 8.0 Re-vamp of evaluation, bringing scores back down so that Crafty *
* will stop sacrificing the exchange, or a piece for two pawns just *
* it thinks it has lots of positional compensation. The next few *
* versions are going to be tuning or coding modifications to eval. *
* *
* 8.1 Futility() re-written to be more efficient, as well as to stop *
* tossing moves out based on the +/- 2 pawn window, which was too *
* speculative. It still saves roughly 20% in speed over the same *
* searches without futility, but seems to have *no* harmful effects *
* in tests run to date. *
* *
* 8.2 Futility() removed once and for all. Since MakeMove() is so *
* fast after the new attack generation algorithm, this was actually *
* slower than not using it. *
* *
* 8.3 EvaluatePawns() weak pawn analysis bug fixed. Other minor *
* performance enhancements and cleanup. *
* *
* 8.4 Dynamic "king tropism" evaluation term now used, which varies *
* based on how exposed the target king is. The more exposed, the *
* larger the bonus for placing pieces near the king. New "analyze" *
* feature that complements the "annotate" feature that Crafty has *
* had for a while. Annotate is used to play over moves that are *
* either in the current game history, or have been read in using *
* the "read <filename>" command. Analyze, on the other hand, will *
* immediately begin searching the current position. Each time the *
* operator enters a move, it will make that move on the board, and *
* then search the resulting position for the other side. In effect *
* this gives a running commentary on a "game in progress". These *
* moves can be pumped into Crafty in many ways so that "on the fly" *
* analysis of a game-in-progress is possible. *
* *
* 8.5 More cleanup. Pawn promotions were searched twice, thanks to the *
* killer moves, although often they resulted in no search overhead *
* due to transposition table hits the second time around. Other *
* minor fixes, including one serious "undefined variable" in *
* Evaluate() that caused grief in endings. *
* *
* 8.6 New book file structure. It is no longer necessary to enter the *
* "number of records" as Crafty now uses a new compressed hashing *
* technique so that the book has no empty space in it, and the size *
* is computed "on the fly" producing a smaller book without the *
* user having to compute the size. Tweaks to Evaluate() to cure *
* minor irritating habits. *
* *
* 8.7 Repaired optimization made in null-move search, that forgot to *
* clear "EnPassant_Target". A double pawn push, followed by a null *
* left the side on move "very confused" and would let it play an *
* illegal enpassant capture in the tree. Sort.<n> files are now *
* removed after book.bin is created. Also, minor change to book *
* format makes it incompatible with older book versions, but also *
* allows book lines to be as long as desired, and the book size to *
* reach any reasonable size. Dynamic king tropism replaced by a *
* dynamic computation, but with a static king tropism score, rather *
* than a score based on king exposure. There was simply too much *
* interaction, although this may prove workable later. *
* *
* 8.8 Tweaks to passed pawn scoring. Scores were too low, making *
* Crafty "ignore" them too much. *
* *
* 8.9 Internal iterative deepening is now used in those rare positions *
* where a PV node has no hash move to search. This does a shallow *
* search to depth-2 to find a good move for ordering. *
* *
* 8.10 Internal interative deepening modified to handle cases where lots *
* of tactics make the deepening search fail high or low, and *
* occasionally end up with no move to try. This produced a "bad *
* move from hash table" error. *
* *
* 8.11 Minor bug in internal iterative deepening fixed. Also, macros *
* for accessing the "position" data structure are now used to make *
* things a little more readable. *
* *
* 8.12 Fixed minor bugs in quiescence checks, which let Crafty include *
* more checks than intended (default quiescence_checks=2, but the *
* comparison was <= before including a check, which made it include *
* three. Additionally, a hashed check was *always* tried, even if *
* quiescence_checks had already been satisfied. Pawn scoring also *
* had a bug, in that there was a "crack" between opening and middle *
* game, where Crafty would conclude that it was in an endgame, and *
* adjust the pawn advance scores accordingly, sometimes causing an *
* odd a4/a5/etc move "out of the blue." Minor bug in next_capture *
* was pruning even exchanges very early in quiescence search. That *
* has now been removed, so only losing exchanges are pruned. *
* *
* 8.13 NextCapture() now *always* tries checking moves if the move at *
* the previous ply was a null-move. This avoids letting the null *
* move hide some serious mating threats. A minor bug where Crafty *
* could draw by repetition after announcing a mate. This was a *
* result of finding a mate score in hash table, and, after the *
* search iteration completed, the mate score would terminate the *
* search completely. Now, the search won't terminate until it *
* finds a mate shorter than the previous search did. Minor eval *
* tweaks and bugfixes as well. *
* *
* 8.14 Checks after null moves discontinued. Worked in some cases, but, *
* in general made the tree larger for nothing. Eval tweaks to stop *
* sacs that resulted in connected passed pawns, often at the *
* expense of a minor piece for a pawn or two, which usually lost. *
* Mobility coeffecient increased for all pieces. Asymmetric king *
* safety discontinued. King safety for both sides is now equally *
* important. King safety is now also proportional to the number of *
* pieces the other side has, so that a disrupted king-side will *
* encourage trading pieces to reduce attacking chances. *
* *
* 8.15 Weak pawn scoring modified further. The changes are designed to *
* cause Crafty to keep pawns "mobile" where they can advance, *
* rather than letting them become blocked or locked. *
* *
* 8.16 Still more weak pawn modifications. In addition, there is no *
* "rook on half-open file" any longer. If there are only enemy *
* pawns on the file, and the most advanced one is weak, then the *
* file is treated as though it were open. Technical error in the *
* EvaluateDevelopment() code that caused screwey evaluations is *
* fixed, making Crafty more likely to castle. :) Book() now *
* verifies that the current position is in book, before trying any *
* moves to see if the resulting positions are in book. This avoids *
* something like e4 e5 Bb5 a6 Nf3 from causing Crafty to play Nc6 *
* which takes it back into book, rather than axb5 winning a piece. *
* This will occasionally backfire and prevent Crafty from trans- *
* posing back into book, but seems safer at present. *
* *
* 8.17 Piece values changed somewhat, to avoid Crafty's propensity to *
* make unfavorable trades. An example: Crafty is faced with the *
* loss of a pawn. Instead, it trades the queen for a rook and *
* bishop, which used to be the same as losing a pawn. This is not *
* so good, and often would result in a slow loss. This version *
* also implements several "user-supplied" patches to make Crafty *
* compile cleanly on various machines. In addition, you no longer *
* have to continually modify types.h for different configurations. *
* the Makefile now supplies a -D<target> to the compiler. You need *
* to edit Makefile and set "target" to the appropriate value from *
* the list provided. Then, when getting a new version, save your *
* Makefile, extract the new source, copy in your makefile and you *
* will be ready, except for those rare occasions where I add a new *
* source module. Other changes are performance tweaks. One is a *
* simple trick to order captures while avoiding Swap() if possible. *
* If the captured piece is more valuable than the capturing piece, *
* we can simply use the difference (pessimistic value) rather than *
* calling Swap() since this pessimistic value is still > 0. Other *
* tweaks to the various Next_*() routines to avoid a little un- *
* necessary work. *
* *
* 8.18 Book move selection algorithm changed. Note that this is highly *
* speculative, but when best book play is selected, Crafty will *
* use the books.bin file as always. If there is no move in books, *
* Crafty reverts to book.bin, but now finds all known book moves *
* and puts them into the root move list. It then does a fairly *
* short search, only considering these moves, and it will play the *
* best one so long as the evaluation is acceptable. If not, it *
* simply returns as though there was no book move, and executes a *
* search as it normally would. The book hashing algorithm was also *
* modified so that the 64-bit hash key is slightly different from *
* the real hash key. In effect, the upper 16 bits are only set as *
* a result of the side-not-to-move's pieces. This means that for a *
* given position, all the book moves will be in the same "cluster" *
* which makes the book dramatically faster, since one seek and read *
* produces all the possible book moves (plus some others too, since *
* the upper 16 bits are not unique enough.) A significant speed *
* improvement is noticable, particularly with a 60mb opening book. *
* Crafty now understands (if that's the right word) that endings *
* with bishops of opposite colors are to be avoided. When such an *
* ending is encountered, the total score is simply divided by two *
* to make the ending look more drawish. *
* *
* 8.19 Book selection algorithm further modified, so that the result of *
* each game in the GM database is known. Now Crafty will not play *
* a move from book, if all games were lost by the side on move, *
* hopefully avoiding many blunders. Crafty now understands how to *
* attack if both players castle on opposite sides, by encouraging *
* pawn advances against the kings. Other minor modifications to *
* the eval values. *
* *
* 8.20 PVS search finally implemented fully. Problems several months *
* ago prevented doing the PVS search along the PV itself. This is *
* therefore quite a bit faster, now that it's fully implemented and *
* working properly. Elapsed time code modified so that Crafty now *
* uses gettimeofday() to get fractions of a second elapsed time. *
* Slight modification time allocation algorithm to avoid using too *
* much time early in the game. *
* *
* 8.21 Courtesy of Mark Bromley, Crafty may run significantly faster on *
* your machine. There are some options in the Makefile that will *
* eliminate many of the large attack computation long longs, which *
* helps prevent cache thrashing. On some machines this will be *
* slower, on others 20% (or maybe more) faster. You'll have to *
* try -DCOMPACT_ATTACKS, and if that's faster, then it's time to *
* try -DUSE_SPLIT_SHIFTS which may help even more. Finally, if you *
* are running on a supersparc processor, you can use the fastattack *
* assembly module fastattack.s and get another big boost. (Attack *
* function is largest compute user in Crafty at present.) Serious *
* search problem fixed. It turns out that Crafty uses the hash *
* table to pass PV moves from one iteration to the next, but for *
* moves at the root of the tree the hash table has no effect, so a *
* special case was added to RootMoveList to check the list of moves *
* and if one matches the PV move, move it to the front of the list. *
* This turned out to be critical because after completing a search, *
* (say to 9 plies) Crafty makes its move, then chops the first two *
* moves off of the PV and then passes that to iterate to start a *
* search. This search starts at lastdepth-1 (8 in this case) since *
* the n-2 search was already done. The "bug" showed up however, in *
* that RootMoveList() was not checking for the PV move correctly, *
* which meant the root moves were ordered by static eval and static *
* exchange evaluation. Normally not a serious problem, just that *
* move ordering is not so good. However, suppose that the opponent *
* takes a real long time to make a move (say 30 seconds) so that *
* Crafty completes a 10 ply search. It then starts the next search *
* at depth=9, but with the wrong move first. If the target time is *
* not large enough to let it resolve this wrong move and get to the *
* other moves on the list, Crafty is "confused" into playing this *
* move knowing absolutely nothing about it. The result is that it *
* can play a blunder easily. The circumstances leading to this are *
* not common, but in a 60 move game, once is enough. PV was pretty *
* well mis-handled in carrying moves from one search to another *
* (not from one iteration to another, but from one complete search *
* to another) and has been fixed. A cute glitch concerning storing *
* PV from one iteration to another was also fixed, where the score *
* stored was confusing the following search. *
* *
* 8.22 EPD support (courtesy of Steven Edwards [thanks]) is now standard *
* in Crafty. For porting, I'll provide a small test run which can *
* be used to validate Crafty once it's been compiled. *
* *
* 8.23 Cleanup/speedup in hashing. HashProbe() and HashStore() now *
* carefully cast the boolean operations to the most efficient size *
* to avoid 64bit operations when only the right 32 bits are *
* significant. RepetitionCheck() code completely re-written to *
* maintain two repetition lists, one for each side. Quiesce() now *
* handles the repetition check a little different, being careful to *
* not call it when it's unimportant, but calling it when *
* repetitions are possible. *
* *
* 8.24 Tweaks for king tropism to encourage pieces to collect near the *
* king, or to encourage driving them away when being attacked. A *
* modification to Evaluate() to address the problem where Crafty *
* is forced to play Kf1 or Kf8, blocking the rook in and getting *
* into tactical difficulties as a result. Book problem fixed where *
* BookUp was attempting to group moves with a common ancestor *
* position together. Unfortunately, captures were separated from *
* this group, meaning capture moves in the book could never be *
* played. If a capture was the only move in book, it sort of *
* worked because Crafty would drop out of book (not finding the *
* capture) and then the search would "save" it. However, if there *
* was a non-capture alternative, it would be forced to play it, *
* making it play gambits, and, often, bad ones. Tablebase support *
* is now in. The tablebase files can be downloaded from the ftp *
* machine at chess.onenet.net, pub/chess/TB. Currently, Steven *
* Edwards has all interesting 4 piece endings done. To make this *
* work, compile with -DTABLEBASES, and create a TB directory where *
* Crafty is run, and locate the tablebase files in that directory. *
* If you are running under UNIX, TB can be a symbolic or hard link *
* to a directory anywhere you want. *
* *
* 8.25 Minor repair on draw by repetition. Modified how books.bin was *
* being used. Now, a move in books.bin has its flags merged with *
* the corresponding move from book.bin, but if the move does not *
* exist in book.bin, it is still kept as a book move. Repetitions *
* are now counted as a draw if they occur two times, period. The *
* last approach was causing problems due to hashing, since the hash *
* approach used in Crafty is fairly efficient and frequently will *
* carry scores across several searches. This resulted in Crafty *
* stumbling into a draw by repetition without knowing. The con- *
* figuration switch HAS-64BITS has been cleaned up and should be *
* set for any 64bit architecture now, not just for Cray machines. *
* *
* 8.26 New search extension added, the well-known "one legal response to *
* check" idea. If there's only one legal move when in check, we *
* extend two plies rather than one, since this is a very forcing *
* move. Also, when one side has less than a rook, and the other *
* has passed pawns, pushing these pawns to the 6th or 7th rank *
* will extend the search one ply, where in normal positions, we *
* only extend when a pawn reaches the 7th rank. *
* *
* 9.0 Minor constraint added to most extensions: we no longer extend *
* if the side on move is either significantly ahead or behind, *
* depending on the extension. For example, getting out of check *
* won't extend if the side on move is a rook behind, since it's *
* already lost anyway. We don't extend on passed pawn pushes if *
* the side on move is ahead a rook, since he's already winning. *
* minor adjustments for efficiency as well. The next few *
* versions in this series will have module names in these comments *
* indicating which modules have been "cleaned" up. This is an *
* effort at optimizing, although it is currently directed at a line *
* by line analysis within modules, rather than major changes that *
* effect more global ideas. This type of optimization will come at *
* a later point in time. *
* *
* 9.1 NextMove(), NextCapture() and NextEvasion() were re-structured *
* to eliminate unnecessary testing and speed them up significantly. *
* EvaluateTrades() was completely removed, since Crafty already has *
* positional scores that encourage/discourage trading based on the *
* status of the game. EvaluateTempo() was evaluated to be a *
* failure and was removed completely. *
* *
* 9.2 Quiesce()) and Search() were modified to be more efficient. In *
* addition, the null-move search was relaxed so that it always does *
* a search to depth-R, even if close to the end of the tree. *
* *
* 9.3 Check() is no longer used to make sure a position is legal after *
* MakeMove() called, but before Search() is called recursively. We *
* now use the same approach as Cray Blitz, we make a move and then *
* capture the king at the next ply to prove the position is not a *
* valid move. If the side-on-move is already in check, we use *
* NextEvasion() which only generates legal moves anyway, so this *
* basically eliminates 1/2 of the calls to Check(), a big win. *
* This resulted in modifications to Search(), Quiesce(), and *
* QuiesceFull(). Connected passed pawns on 6th-7th no longer *
* trigger search extensions. Solved some problems like Win at *
* Chess #2, but overall was a loser. *
* *
* 9.4 Lookup now checks the transposition table entry and then informs *
* Search() when it appears that a null move is useless. This is *
* found when the draft is too low to use the position, but it is at *
* least as deep as a null-move search would go, and the position *
* did not cause a fail-high when it was stored. King-safety was *
* modified again. The issue here is which king should attract the *
* pieces, and for several months the answer has been the king that *
* is most exposed attracts *all* pieces. This has been changed to *
* always attract one side's pieces to the other king. Crafty's *
* asymmetric king-safety was making it overly-defensive, even when *
* the opponent's king was more exposed. This should cure that and *
* result in more aggressive play. *
* *
* 9.5 "Vestigial code" (left over from who-knows-when) removed from *
* Evaluate(). This code used an undefined variable when there was *
* no bishop or knight left on the board, and could add in a penalty *
* on random occasions. Quiescence checks removed completely to see *
* how this works, since checks extend the normal search significant *
* amounts in any case. QuiesceFull() removed and merged into *
* Quiesce() which is faster and smaller. First impression: faster, *
* simpler, better. The benefit of no quiescence checks is that the *
* exhaustive search goes deeper to find positional gains, rather *
* than following checks excessively. No noticable loss in tactical *
* strength (so far). *
* *
* 9.6 legal move test re-inserted in Search() since null-moves could *
* make it overlook the fact that a move was illegal. New assembly *
* code for X86 improves performance about 1/3, very similarly to *
* the results obtained with the sparc-20 assembly code. This was *
* contributed by Eugene Nalimov and is a welcome addition. *
* *
* 9.7 Optimizations continuing. Minor bug in pawn evaluation repaired. *
* Crafty looked at most advanced white pawn, but least-advanced *
* black pawn on a file when doing its weak pawn evaluation. The *
* history heuristic was slightly broken, in that it was supposed to *
* be incrementing the history count by depth*depth, but this was *
* somehow changed to 7*depth, which was not as good. Assembly *
* language interface fixed to cleanly make Crafty on all target *
* architectures. *
* *
* 9.8 The first change was to borrow a time-allocation idea from Cray *
* Blitz. Essentially, when Crafty notices it has used the normal *
* time allotment, rather than exiting the search immediately, it *
* will wait until it selects the next move at the root of the tree. *
* The intent of this is that if it has started searching a move *
* that is going to be better than the best found so far, this will *
* take more time, while a worse move will fail low quickly. Crafty *
* simply spends more time to give this move a chance to fail high *
* or else quickly fail low. A fairly serious bug, that's been *
* around for a long time, has finally been found/fixed. In simple *
* terms, if the "noise" level was set too high, it could make *
* Crafty actually play a bad move. The more likely effect was to *
* see "bad move hashed" messages and the first few lines of output *
* from the search often looked funny. The bug was "noise" was used *
* as a limit, until that many nodes had been searched, no output *
* would be produced. Unfortunately, on a fail-high condition, the *
* same code that produced the "++ Nh5" message also placed the *
* fail-high move in the PV. Failing to do this meant that the *
* search could fail high, but not play the move it found. Most *
* often this happened in very fast games, or near the end of long *
* zero-increment games. It now always saves this move as it should *
* regardless of whether it prints the message or not. *
* *
* 9.9 Interface to Xboard changed from -ics to -xboard, so that -ics *
* can be used with the custom interface. Additional code to *
* communicate with custom interface added. Search() extensions are *
* restricted so that there can not be more than one extension at a *
* node, rather than the two or (on occasion) more of the last *
* version. *
* *
* 9.10 Converted to Ken Thompson's "Belle" hash table algorithm. Simply *
* put, each side has two tables, one that has entries replaced on a *
* depth-priority only, the other is an "always replace" table, but *
* is twice as big. This allows "deep" entries to be kept along *
* with entries close to search point. Basically, when the depth- *
* priority table gets a position stored in it, the displaced *
* position is moved to the always-replace table. If the position *
* can not replace the depth-priority entry, it always overwrites *
* the other always-replace entry. However, a position is never put *
* in both tables at the same time. *
* *
* 9.11 Bug in Search() that could result in the "draft" being recorded *
* incorrectly in the hash table. Caused by passing depth, which *
* could be one or two plies more than it should be due to the last *
* move extending the search. RepetitionCheck() completely removed *
* from Quiesce() since only capture moves are included, and it's *
* impossible to repeat a position once a capture has been made. *
* *
* 9.12 optimizations: history.c, other minor modifications. *
* *
* 9.13 EvaluatePawns() modified significantly to simplify and be more *
* accurate as well. Pawns on open files are now not directly *
* penalized if they are weak, rather the penalty is added when the *
* rooks are evaluated. Pawn hashing modified to add more info to *
* the data that is hashed. King safety scores toned down almost *
* 50% although it is still asymmetric. *
* *
* 9.14 EvaluatePawns() modified further so that it now does the same *
* computations for king safety as the old EvaluateKingSafety*() *
* modules did, only it produces four values, two for each king, *
* for each side of the board (king or queen-side). This is now *
* hashed with the rest of the pawn scoring, resulting in less *
* hashing and computation, and more hits for king-safety too. King *
* safety modified further. Asymmetric scoring was accidentally *
* disabled several versions ago, this is now enabled again. *
* *
* 9.15 Evaluate() now attempts to recognize the case where a knight is *
* trapped on one of the four corner squares, much like a bishop *
* trapped at a2/a7/h2/h7. If a knight is on a corner square, and *
* neither of the two potential flight squares are safe (checked by *
* Swap()) then a large penalty is given. This was done to avoid *
* positions where Crafty would give up a piece to fork the king and *
* rook at (say) c7, and pick up the rook at a8 and think it was an *
* exchange ahead, when often the knight was trapped and it was *
* two pieces for a rook and pawn (or worse.) Two timing bugs fixed *
* in this version: (1) nodes_per_second was getting clobbered at *
* the end of iterate, which would then corrupt the value stored in *
* nodes_between_time_checks and occasionally make Crafty not check *
* the time very often and use more time than intended; (2) the *
* "don't stop searching after time is out, until the current move *
* at the root of the tree has been searched" also would let Crafty *
* use time unnecessarily. *
* *
* 9.16 Significant changes to the way MakeMove() operates. Rather than *
* copying the large position[ply] structure around, the piece *
* location bitmaps and the array of which piece is on which square *
* are now simple global variables. This means that there is now an *
* UnmakeMove() function that must be used to restore these after a *
* a move has been made. The benefit is that we avoid copying 10 *
* bitmaps for piece locations when typically only one is changed, *
* Ditto for the which piece is on which square array which is 64 *
* bytes long. The result is much less memory traffic, with the *
* probability that the bitmaps now stay in cache all the time. The *
* EvaluatePawns() code now has an exponential-type penalty for *
* isolated pawns, but it penalizes the difference between white and *
* black isolated pawns in this manner. King evaluation now *
* evaluates cases where the king moves toward one of the rooks and *
* traps it in either corner. *
* *
* 9.17 Xboard compatibility version! Now supports, so far as I know, *
* the complete xboard interface, including hint, show thinking, *
* taking back moves, "move now" and so forth. Additionally, Crafty *
* now works with standard xboard. Notice that this means that a *
* ^C (interrupt) will no long terminate Crafty, because xboard uses *
* this to implement the "move now" facility. This should also *
* work with winboard and allow pondering, since there is now a *
* special windows version of CheckInput() that knows how to check *
* Win95 or WinNT pipes when talking with winboard. *
* *
* 9.18 Xboard compatibility update. "force" (gnu) mode was broken, so *
* that reading in a PGN file (via xboard) would break. Now, Crafty *
* can track the game perfectly as xboard reads the moves in. King *
* safety modified to discourage g3/g6 type moves without the bishop *
* to defend the weak squares. Significant other changes to the *
* Evaluate() procedure and its derivatives. Very nasty trans/ref *
* bug fixed. Been there since transposition tables added. When *
* storing a mate score, it has to be adjusted since it's backed up *
* as "mate in n plies from root" but when storing, it must be saved *
* as "mate in n plies from current position". Trivial, really, but *
* I overlooked one important fact: mate scores can also be upper *
* or lower search bounds, and I was correcting them in the same way *
* which is an error. The effect was that Crafty would often find a *
* mate in 2, fail high on a move that should not fail high, and end *
* up making a move that would mate in 3. In particularly bad cases *
* this would make the search oscillate back and forth and draw a *
* won position. The fix was to only adjust the score if it's a *
* score, not if it's a bound. The "age" field of the trans/ref *
* table was expanded to 3 bits. Iterate now increments a counter *
* modulo 8, and this counter is stored in the 3 ID bits of the *
* trans/ref table. If they are == the transposition_id counter, *
* we know that this is a position stored during the current search. *
* If not, it's an "old" position. This avoids the necessity of *
* stepping through each entry in the trans/ref table (at the begin- *
* ning of a search) to set the age bit. Much faster in blitz games *
* as stepping through the trans/ref table, entry by entry, would *
* blow out cache. This idea was borrowed from Cray Blitz, which *
* used this same technique for many years. *
* *
* 9.19 New evaluation code for passed pawns. Crafty now gives a large *
* bonus for two or more connected passed pawns, once they reach the *
* sixth rank, when the opponent has less than a queen remaining. *
* this will probably be tuned as experience produces the special *
* cases that "break" it. Such things as the king too far away or *
* the amount of enemy material left might be used to further im- *
* prove the evaluation. *
* *
* 9.20 Bug in SetBoard() fixed. Validity checks for castling status and *
* en passant status was broken for castle status. It was checking *
* the wrong rook to match castling status, and would therefore not *
* accept some valid positions, including #8 in Win At Chess suite. *
* Minor repetition bug fixed, where Crafty would recognize that a *
* three-fold repetition had occurred, but would not claim it when *
* playing on a chess server. Crafty now does not immediately re- *
* search the first move when it fails low. Rather, it behaves like *
* Cray Blitz, and searches all moves. If all fail low, Crafty will *
* then relax (lower) alpha and search the complete list again. *
* This is a simple gamble that there is another move that will *
* "save the day" so that we avoid the overhead of finding out just *
* how bad the first move is, only to have more overhead when a good *
* move fails high. Minor repetition bug fixed. When running test *
* suites of problems, SetBoard() neglected to put the starting *
* position in the repetition list, which would occasionally waste *
* time. One notable case was Win At Chess #8, where Crafty would *
* find Nf7+ Kg8 Nh6+ Kh8 (repeating the original position) followed *
* by Rf7 (the correct move, but 4 tempi behind.) Display() bug *
* fixed. Crafty now displays the current board position, rather *
* than the position that has been modified by a search in progress. *
* Castling evaluation modified including a bug in the black side *
* that would tend to make Crafty not castle queen-side as black if *
* the king-side was shredded. Minor bug in Book(). If the book was *
* turned off (which is done automatically when using the test com- *
* mand since several of the Win At Chess positions are from games *
* in Crafty's large opening book) Book() would still try to read *
* the file and then use the data from the uninitialized buffer. *
* This would, on occasion, cause Crafty to crash in the middle of *
* a test suite run. *
* *
* 9.21 Castling evaluation has been significantly modified to handle the *
* following three cases better: *
* (a) One side can castle at the root of the tree, but can not *
* castle at a tip position. If the move that gave up the right to *
* castle was *not* a castle move, penalize the score. *
* (b) One side can castle short or long at the root, but has al- *
* ready castled by the time the search reaches a tip position. *
* Here the goal is to make sure the player castled to the "better" *
* side by comparing king safety where the king really is, to king *
* safety had the king castled to the other side. If the latter is *
* "safer" then penalize the current position by the "difference" *
* in king safety to encourage that side to delay castling. This is *
* a problem when Crafty can castle kingside *now*, but the kingside *
* has been disrupted somehow. If the search is not deep enough to *
* see clearing out the queenside and castling long, then it will *
* often castle short rather than not castle at all. This fix will *
* make it delay, develop the queenside, and castle to a safer king *
* shelter, unless tactics force it to castle short. *
* (c) One side can castle short or long at the root, but can only *
* castle one way at a tip position, because a rook has been moved. *
* If the remaining castle option is worse than castling to the side *
* where the rook was moved, then we penalize the rook move to keep *
* castling to that side open as an option. *
* *
* 9.22 More castling evaluation changes, to tune how/when Crafty chooses *
* to castle. Bugs in Option() where certain commands could be ex- *
* ecuted while a search was in progress. If these commands did *
* anything to the board position, It would break Crafty badly. *
* All that was needed was to check for an active search before some *
* commands were attempted, and if a search was in progress, return *
* to abort the search then re-try the command. When playing games *
* with computers (primarily a chess-server consideration) Crafty is *
* now defaulting to "book random 0" to use a short search to help *
* avoid some ugly book lines on occasion. In this version, *all* *
* positional scores were divided by 2 to reduce the liklihood that *
* Crafty would sacrifice material and make up the loss with some *
* sort of positional gain that was often only temporary. Note that *
* king safety scores were not reduced while doing this. New book *
* random options: 0=search, 1=most popular move, 2=move that *
* produces best positional value, 3=choose from most frequently *
* played moves, 4=emulate GM frequency of move selection, 5=use *
* sqrt() on frequencies to give more randomness, 6=random. For *
* now, computers get book_random=1, while GM's now get 4 (same as *
* before), everyone else gets 5. Until now, there has been no *
* penalty for doubled/tripled pawns. It now exists. Also, if the *
* king stands on E1/E8, then the king-side king safety term is used *
* to discourage disrupting the king-side pawns before castling. *
* Crafty now has a start-up initialization file (as most Unix *
* programs do). This file is named ".craftyrc" if the macro UNIX *
* is defined, otherwise a "dossy" filename "crafty.rc" is used. *
* Crafty opens this file and executes every command in it as though *
* they were typed by the operator. The last command *must* be *
* "exit" to revert input back to STDIN. *
* *
* 9.23 More evaluation tuning, including the complete removal of the *
* mobility term for rooks/queens. Since rooks already have lots *
* of scoring terms like open files, connected, etc, mobility is *
* redundant at times and often misleading. The queen's mobility *
* is so variable it is nearly like introducing a few random points *
* at various places in the search. Minor Xboard compatibility bug *
* fixed where you could not load a game file, then have Crafty play *
* by clicking the "machine white" or "machine black" options. *
* *
* 9.24 Minor bug in Quiesce() repaired. When several mate-in-1 moves *
* were available at the root, Crafty always took the last one, *
* which was often an under-promotion to a rook rather than to a *
* queen. It looked silly and has been fixed so that it will play *
* the first mate-in-1, not the last. RootMoveList() went to great *
* pains to make sure that promotion to queen occurs before rook. *
* Bug in EvaluateOutsidePassedPawns() would fail to recognize that *
* one side had an outside passer, unless both sides had at least *
* one passer, which failed on most cases seen in real games. *
* Minor "tweak" to move ordering. GenerateMoves() now uses the *
* LSB() function to enumerate white moves, while still using MSB() *
* for black moves. This has the effect of moving pieces toward *
* your opponent before moving them away. A severe oversight *
* regarding the use of "!" (as in wtm=!wtm) was found and corrected *
* to speed things up some. !wtm was replaced by wtm^1 (actually, *
* a macro Flip(wtm) is used to make it more readable) which *
* resulted in significant speedup on the sparc, but a more modest *
* improvement on the pentium. *
* *
* 9.25 Minor bug in Book() fixed where it was possible for Crafty to *
* play a book move that was hardly ever played. Minor change to *
* time utilization to use a little more time "up front". Tuned *
* piece/square tables to improve development some. Saw Crafty lose *
* an occasional game because (for example) the bishop at c1 or c8 *
* had not moved, but the king had already castled, which turned the *
* EvaluateDevelopment() module "off". first[ply] removed, since it *
* was redundant with last[ply-1]. The original intent was to save *
* a subscript math operation, but the compilers are quite good with *
* the "strength-reduction" optimization, making referencing a value *
* by first[ply] or last[ply-1] exactly the same number of cycles. *
* Passed pawn scores increased. The reduction done to reduce all *
* scores seemed to make Crafty less attentive to passed pawns and *
* the threats they incur. Minor bug in Book() fixed, the variable *
* min_percent_played was inoperative due to incorrect test on the *
* book_status[n] value. Pawn rams now scored a little differently, *
* so that pawn rams on Crafty's side of the board are much worse *
* than rams elsewhere. This avoids positional binds where, for ex- *
* ample Crafty would like black with pawns at e6 d5 c6, white with *
* pawns at e5 and c5. Black has a protected passed pawn at d5 for *
* sure, but the cramp makes it easy for white to attack black, and *
* makes it difficult for black to defend because the black pawns *
* block the position badly. King safety tweaked up about 30%, due *
* to using nearly symmetrical scoring, the values had gotten too *
* small and were not overriding minor positional things. *
* *
* 9.26 Minor bug fixes in time allocation. This mainly affects Crafty *
* as it plays on a chess server. The problem is, simply, that the *
* current internal timing resolution is 1/10 of a second, kept in *
* an integer variable. .5 seconds is stored as 5, for example. *
* This became a problem when the target time for a search dropped *
* below .3 seconds, because the "easy move" code would terminate *
* the search after 1/3 of the target time elapsed if there were no *
* fail lows or PV changes. Unfortunately, 2 divided by 3 (.2 secs *
* /3) is "zero" which would let the search quickly exit, possibly *
* without producing a PV with a move for Crafty to play. Crafty *
* would play the first PV move anyway, which was likely the PV move *
* from the last search. This would corrupt the board information, *
* often produce the error "illegal move" when the opponent tried to *
* move, or, on occasion, blow Crafty up. On a chess server, Crafty *
* would simply flag and lose. After this fix, I played several *
* hundred games with a time control of 100 moves in 1 second and *
* there were no failures. Before the fix, this time control could *
* not result in a single completed game. If you don't run Crafty *
* on a chess server, this version is not important, probably. a *
* minor fix for move input, so that moves like e2e4 will always be *
* accepted, where before they would sometimes be flagged as errors. *
* *
* 9.27 This version has an interesting modification to NextCapture(). *
* Quiesce() now passes alpha to NextCapture() and if a capture *
* appears to win material, but doesn't bring the score up to the *
* value of alpha, the capture is ignored. In effect, if we are so *
* far behind that a capture still leaves us below alpha, then there *
* is nothing to gain by searching the capture because our opponent *
* can simply stand pat at the next ply leaving the score very bad. *
* One exception is if the previous ply was in check, we simply look *
* for any safe-looking capture just in case it leads to mate. Bad *
* book bug with book random=1 or 2 fixed (this is set when playing *
* a computer). This bug would cause Crafty to play an illegal move *
* and bust wide open with illegal move errors, bad move hashed, and *
* other things. Book randomness also quite a bit better now. *
* *
* 9.28 Piece/square table added for rooks. Primary purpose is to dis- *
* courage rooks moving to the edge of the board but in front of *
* pawns, where it is easy to trap it. Crafty now understands the *
* concept of blockading a passed pawn to prevent it from advancing. *
* it always understood that advancing one was good, which would *
* tend to encourage blockading, but it would also often ignore the *
* pawn and let it advance a little here, a little there, until it *
* suddenly realized that it was a real problem. The command to set *
* the size of the hash table has been modified. This command is *
* now "hash n", "hash nK" or "hash nM" to set the hash table to one *
* of bytes, Kbytes, or Mbytes. Note that if the size is not an *
* exact multiple of what Crafty needs, it silently reduces the size *
* to an optimum value as close to the suggested size as possible. *
* Trade bonus/penalty is now back in, after having been removed *
* when the new UnmakeMove() code was added. Crafty tries to trade *
* pawns but not pieces when behind, and tries to trade pieces but *
* not pawns when ahead. EvaluateDraws() now understands that rook *
* pawns + the wrong bishop is a draw. Minor adjustment to the *
* quiescence-search pruning introduced in 9.27, to avoid excluding *
* captures that didn't lose material, but looked bad because the *
* positional score was low. Slightly increased the values of the *
* pieces relative to that of a pawn to discourage the tendency to *
* trade a piece for two or three pawns plus some positional plusses *
* that often would slowly vanish. Null-move search modified to try *
* null-moves, even after captures. This seems to hurt some prob- *
* lem positions, but speeds up others significantly. Seems better *
* but needs close watching. EvaluateDraws() call moved to the top *
* of Evaluate() to check for absolute draws first. Quiesce() now *
* always calls Evaluate() which checks for draws before trying the *
* early exit tests to make sure that draws are picked up first. *
* EvaluateDraws() substantially re-written to get rid of lots of *
* unnecessary instructions, and to also detect RP+B of wrong color *
* even if the losing side has a pawn of its own. Crafty would *
* often refuse to capture that last pawn to avoid reaching an end- *
* game it knew was drawn. *
* *
* 9.29 New time.c as contributed by Mike Byrne. Basically makes Crafty *
* use more time up front, which is a method of anticipating that *
* Crafty will predict/ponder pretty well and save time later on *
* anyway. InCheck() is never called in Quiesce() now. As a *
* result, Crafty won't recognize mates in the q-search. This has *
* speeded the code up with no visible penalty, other than it will *
* occasionally find a win of material rather than a mate score, but *
* this has not affected the problem suite results in a measurable *
* way, other than Crafty is now about 10% faster in average type *
* position, and much faster in others. The latest epd code from *
* Steven Edwards is a part of this version, which includes updated *
* tablebase access code. *
* *
* 10.0 New time.c with a "monitoring feature" that has two distinct *
* functions: (1) monitor Crafty's time remaining and if it is too *
* far behind the opponent, force it to speed up, or if it is well *
* ahead on time, slow down some; (2) if opponent starts moving *
* quickly, Crafty will speed up as well to avoid getting too far *
* behind. EvaluateDraws() modified to detect that if one side has *
* insufficient material to win, the score can never favor that side *
* which will make Crafty avoid trading into an ending where it has *
* KNN vs KB for example, where KNN seems to be ahead. *
* *
* 10.1 New book.c. Crafty now counts wins, losses and draws for each *
* possible book move and can use these to play a move that had a *
* high percentage of wins, vs the old approach of playing a move *
* just because it was played a lot in the past. *
* *
* 10.2 Evaluation tuning. Rook on 7th, connected rooks on 7th, etc., *
* are now more valuable. Crafty was mistakenly evaluating this *
* too weakly. Book() changed so that the list of moves is first *
* sorted based on winning percentages, but then, after selecting *
* the sub-set of this group, the list is re-sorted based on the *
* raw total games won so that the most popular opening is still the *
* most likely to be played. *
* *
* 10.3 Timer resolution changed to 1/100th of a second units, with all *
* timing variables conforming to this, so that it is unnecessary *
* to multiply by some constant to convert one type of timing info *
* to the standard resolution. Bug in evaluate.c fixed. Trapped *
* rook (rook at h1, king at g1 for example) code had a bad sub- *
* script that caused erroneous detection of a trapped rook when *
* there was none. *
* *
* 10.4 Quiesce() no longer checks for time exceeded, nor does it do any *
* hashing whatsoever, which makes it significantly faster, while *
* making the trees only marginally bigger. *
* *
* 10.5 Quiesce() now calls GenerateCaptures() to generate capture moves. *
* This new move generator module is significantly faster, which *
* speeds the quiescence search up somewhat. *
* *
* 10.6 CastleStatus is now handled slightly differently. The right two *
* bits still indicate whether or not that side can castle to either *
* side, and 0 -> no castling at all, but now, <0 means that no *
* castling can be done, and that castling rights were lost by *
* making a move that was not castling. This helps in Evaluate() *
* by eliminating a loop to see if one side castled normally or had *
* to give up the right to castle for another (bad) reason. This is *
* simply an efficiency issue, and doesn't affect play or anything *
* at all other than to make the search faster. *
* *
* 10.7 NextMove() now doesn't try history moves forever, rather it will *
* try the five most popular history moves and if it hasn't gotten a *
* cutoff by then, simply tries the rest of the moves without the *
* history testing, which is much faster. *
* *
* 10.8 Book() now "puzzles" differently. In puzzling, it is trying to *
* find a move for the opponent. Since a book move by the opponent *
* will produce an instant move, puzzle now enumerates the set of *
* legal opponent moves, and from this set, removes the set of known *
* book moves and then does a quick search to choose the best. We *
* then ponder this move just in case the opponent drops out of book *
* and uses a normal search to find a move. Crafty now penalizes *
* a pawn that advances, leaving its neighbors behind where both *
* the advancing pawn, and the ones being left behind become weaker. *
* the opening phase of the game has been modified to "stay active" *
* until all minor pieces are developed and Crafty has castled, to *
* keep EvaluateDevelopment() active monitoring development. Minor *
* change to DrawScore() so that when playing a computer, it will *
* return "default_draw_score" under all circumstances rather than *
* adjusting this downward, which makes Crafty accept positional *
* weaknesses rather than repeat a position. *
* *
* 10.9 Evaluate() now handles king safety slightly differently, and *
* increases the penalty for an exposed king quite a bit when there *
* is lots of material present, but scales this increase down as the *
* material comes off. This seems to help when attacking or getting *
* attacked. Since Quiesce() no longer probes the hash table, the *
* idea of storing static evaluations there became worthless and was *
* burning cycles that were wasted. This has been removed. Check *
* extensions relaxed slightly so that if ply is < iteration+10 it *
* will allow the extension. Old limit was 2*iteration. Connected *
* passed pawns on 6th now evaluated differently. They get a 1 pawn *
* bonus, then if material is less than a queen, another 1 pawn *
* bonus, and if not greater than a rook is left, and the king can't *
* reach the queening square of either of the two pawns, 3 more *
* more pawns are added in for the equivalent of + a rook. *
* *
* 10.10 Evaluate() modified. King safety was slightly broken, in that *
* an uncastled king did not get a penalty for open center files. *
* new evaluation term for controlling the "absolute 7th rank", a *
* concept from "My System". *
* *
* 10.11 Lazy evaluation implemented. Now as the Evaluate() code is ex- *
* ecuted, Crafty will "bail out" when it becomes obvious that the *
* remainder of the evaluation can't bring the score back inside the *
* alpha/beta window, saving time. *
* *
* 10.12 More Jakarta time control commands added so operator can set the *
* time accurately if something crashes, and so the operator can set *
* a "cushion" to compensate for operator inattention. "Easy" is *
* more carefully qualified to be a recapture, or else a move that *
* preserves the score, rather than one that appears to win material *
* as was done in the past. King safety tweaked a little so that if *
* one side gives up the right to castle, and could castle to a safe *
* position, the penalty for giving up the right is substantially *
* larger than before. A minor bug also made it more likely for *
* black to give up the right to castle than for white. *
* *
* 10.13 Modifications to Book() so that when using "book random 0" mode *
* (planned for Jakarta) and the search value indicates that we are *
* losing a pawn, we return "out of book" to search *all* the moves, *
* Not just the moves that are "in book." This hopefully avoids *
* some book lines that lose (gambit) material unsoundly. *
* *
* 10.14 Final timing modifications. Puzzling/booking searches now take *
* 1/30th of the normal time, rather than 1/10th. New command *
* "mode=tournament" makes Crafty assess DRAW as "0" and also makes *
* it prompt the operator for time corrections as required by WMCCC *
* rules. *
* *
* 10.15 Evaluate() tuning to reduce development bonuses, which were able *
* to overwhelm other scores and lead to poor positions. *
* *
* 10.16 "Lazy" (early exit) caused some problems in Evaluate() since so *
* many scores are very large. Scaled this back significantly and *
* also EvaluateOutsidePassedPawns() could double the score if one *
* side had passers on both sides. This was fixed. *
* *
* 10.17 Crafty's Book() facility has been significantly modified to be *
* more understandable. book random <n> has the following options: *
* (0) do a search on set of book moves; (1) choose from moves that *
* are played most frequently; (2) choose from moves with best win *
* ratio; (3) choose from moves with best static evaluation; and *
* (4) choose completely randomly. book width <n> can be used to *
* control how large the "set" of moves will be, with the moves in *
* the "set" being the best (according to the criteria chosen) from *
* the known book moves. Minor tweak to Search() so that it extends *
* passed pawn pushes to the 6th or 7th rank if the move is safe, *
* and this is an endgame. *
* *
* 10.18 New annotate command produces a much nicer analysis file and also *
* lets you exert control over what has to happen to trigger a com- *
* ment among other things. AKA Crafty/Jakarta version. *
* *
* 11.1 Fractional depth allows fractional ply increments. The reso- *
* lution is 1/4 of a ply, so all of the older "depth++" lines now *
* read depth+=PLY, where #define PLY 4 is used everywhere. This *
* gives added flexibility in that some things can increment the *
* depth by < 1 ply, so that it takes two such things before the *
* search actually extends one ply deeper. Crafty now has full PGN *
* support. A series of pgn commands (pgn Event 14th WMCCC) allow *
* the PGN tags to be defined, when Crafty reads or annotates a PGN *
* file it reads and parses the headers and will display the info *
* in the annotation (.can) file or in the file you specify when you *
* execute a "savegame <filename>" command. *
* *
* 11.2 Fractional ply increments now implemented. 11.1 added the basic *
* fractional ply extension capabilities, but this version now uses *
* them in Search(). There are several fractional ply extensions *
* being used, all are #defined in types.h to make playing with them *
* somewhat easier. One advantage is that now all extensions are *
* 3/4 of a ply, which means the first time any extension is hit, it *
* has no effect, but the next three extensions will result in an *
* additional ply, followed by another ply where the extension does *
* nothing, followed by ... This allowed me to remove the limit on *
* how deep in the tree the extensions were allowed, and also seems *
* to not extend as much unless there's "something" going on. When *
* the position gets interesting, these kick in. Asymmetric king *
* safety is back in. Crafty's king safety is a little more im- *
* portant than the opponent's now to help avoid getting its king- *
* side shredded to win a pawn. A new term, ROOK_ON_7TH_WITH_PAWN *
* to help Crafty understand how dangerous a rook on the 7th is if *
* it is supported by a pawn. It is difficult to drive off and the *
* pawn provides additional threats as well. *
* *
* 11.3 King safety modifications. One fairly serious bug is that Crafty *
* considered that king safety became unimportant when the total *
* pieces dropped below 16 material points. Note that this was *
* pieces only, not pieces and pawns, which left plenty of material *
* on the board to attack with. As a result, Crafty would often *
* allow its king-side to be weakened because it was either in an *
* endgame, or close to an endgame. *Incorrectly*, it turns out. :) *
* Going back to a very old Crafty idea, king tropism is now tied to *
* how exposed each king is, with pieces being attracted to the most *
* exposed king for attack/defense. *
* *
* 11.4 Tuning on outside passed pawn code. Values were not large enough *
* and didn't emphasize how strong such a pawn is. General passed *
* pawn value increased as well. Minor bug in edit that would let *
* Crafty flag in some wild games was fixed. Basically, edit has no *
* way to know if castling is legal, and has to assume if a rook and *
* king are on the original squares, castling is o.k. For wild2 *
* games in particular, this can fail because castling is illegal *
* (by the rules for wild 2) while it might be that rooks and king *
* are randomly configured to make it look possible. Crafty would *
* then try o-o or o-o-o and flag when the move was rejected as *
* illegal. richard Lloyd suggested a speed-up for the annotate *
* command which I'm using temporarily. Crafty now searches all *
* legal moves in a position, and if the best move matches the game *
* move, the second search of just the move played is not needed. I *
* was searching just the game move first, which was a waste of time *
* in many positions. I'll resume this later, because I want to see *
* these values: (1) score for move actually played; (2) score for *
* the rest of the moves only, not including the move actually *
* played, to see how often a player finds a move that is the *only* *
* good move in a position. *
* *
* 11.5 More fractional ply extension tuning. A few positions could blow *
* up the search and go well beyond 63 plies, the max that Crafty *
* can handle. Now, extensions are limited to no more than one ply *
* of extensions for every ply of search. Note that "in check" is *
* extended on the checking move ply, not on the out of check ply, *
* so that one-reply-to-check still extends further. Minor changes *
* to time.c to further help on long fast games. Another important *
* timing bug repaired. If Crafty started an iteration, and failed *
* high on the first move, it would not terminate the search until *
* this move was resolved and a score returned. This could waste a *
* lot of time in already won positions. Interesting bug in the *
* capture search pruning fixed. At times, a piece would be hung, *
* but the qsearch would refuse to try the capture because it would *
* not bring the score back to above alpha. Unfortunately, taking *
* the piece could let passed pawns race in undisturbed which would *
* affect the score. This pruning is turned off when there are not *
* at least two pieces left on the board. Another bug in the move *
* generator produced pawn promotions twice, once when captures were *
* generated, then again when the rest of the moves are produced. *
* this was also repaired. Small book now will work. The BookUp() *
* code now assumes white *and* black won in the absence of a valid *
* PGN Result tag, so that the small book will work correctly. *
* *
* 11.6 Modifications to time allocation in a further attempt to make *
* Crafty speed up if time gets short, to avoid flagging. It is now *
* *very* difficult to flag this thing. :) Minor evaluation tweaks *
* and a fix to Quiesce() to speed it up again after a couple of bad *
* fixes slowed things down. *
* *
* 11.7 Minor modification to Evaluate(). Rooks behind a passed pawn are *
* good, but two rooks behind the pawn don't help if the pawn is *
* blockaded and can't move, unless the two rooks are not the same *
* color as the pawn. *
* *
* 11.8 First stage of "book learning" implemented. Crafty monitors the *
* search evaluation for the first 10 moves out of book. It then *
* computes a "learn value" if it thinks this set of values shows *
* that the book line played was very good or very bad. This value *
* is added to a "learn count" for each move in the set of book *
* moves it played, with the last move getting the full learn value, *
* and moves closer to the start of the game getting a smaller *
* percentage. (See learn.c for more details). These values are *
* used by Book() to help in selecting/avoiding book lines. Crafty *
* produces a "book.lrn" file that synthesizes this information into *
* a portable format that will be used by other Crafty programs, *
* once the necessary code is added later on. *
* *
* 11.9 An age-old problem caused by null-move searching was eliminated *
* in this version. Often the null-move can cause a move to fail *
* high when it should not, but then the move will fail low on the *
* re-search when beta is relaxed. This would, on occasion, result *
* in Crafty playing a bad move for no reason. Now, if a fail high *
* is followed by a fail-low, the fail high condition is ignored. *
* This can be wrong, but with null-move pruning, it can also be *
* even "more wrong" to accept a fail high move after it fails low *
* due to a null-move failure, than it would be right to accept the *
* fail high/fail low that is caused by trans/ref table anomalies. *
* *
* 11.10 Crafty is now using the Kent, et. al, "razoring" algorithm, which *
* simply eliminates the last ply of full-width searching and goes *
* directly to the capture search if the move before the last full- *
* width ply is uninteresting, and the Material eval is 1.5 pawns *
* below alpha. It's a "modest futility" idea that doesn't give up *
* on the uninteresting move, but only tries captures after the move *
* is played in the tree. Net result is 20-30% average faster times *
* to reach the same depth. Minor mod to book.lrn to include Black, *
* White and Date PGN tags just for reference. Next learning mod is *
* another "book random n" option, n=3. This will use the "learned" *
* score to order book moves, *if* any of them are > 0. What this *
* does is to encourage Crafty to follow opening lines that have *
* been good, even if the learn count hasn't reached the current *
* threshold of 1,000. This makes learning "activate" faster. This *
* has one hole in it, in that once Crafty learns that one move has *
* produced a positive learn value, it will keep playing that move *
* (since no others will yet have a positive value) until it finally *
* loses enough to take the learn value below zero. This will be *
* taken care of in the next version, hopefully. *
* *
* 11.11 New "book random 4" mode that simply takes *all* learning scores *
* for the set of legal book moves, translates them so that the *
* worst value is +1 (by adding -Min(all_scores)+1 to every learn *
* value) and then squaring the result. This encourages Crafty to *
* follow book lines that it has learned to be good, while still *
* letting it try openings that it has not yet tried (learn value *
* =0) and even lets it try (albeit rarely) moves that it has *
* learned to be bad. Minor evaluation tweaking for king placement *
* in endgames to encourage penetration in the center rather than on *
* a wing where the king might get too far from the "action." *
* *
* 11.12 LearnFunction() now keeps positional score, rather than using a *
* constant value for scores < PAWN_VALUE, to improve learning *
* accuracy. Book learn <filename> [clear] command implemented to *
* import learning files from other Crafty programs. *
* *
* 11.13 Endgame threshold lowered to the other side having a queen or *
* less (9) rather than (13) points. Queen+bishop can be very *
* dangerous to the king for example, or two rooks and a bishop. *
* Learning "curve" modified. It was accidentally left in a sort *
* of "geometric" shape, with the last move getting the full learn *
* value, the next one back getting 1/2, the next 1/3, etc. Now *
* it is uniformly distributed from front to back. If there are 20 *
* moves, the last gets the full value, the next gets 19/20, etc.. *
* Also the "percentage played" was hosed and is fixed. *
* *
* 11.14 Minor modification to book learn 4 code so that when you start *
* off with *no* learned data, Book() won't exclude moves from the *
* possible set of opening moves just because one was not played *
* very often. Due to the lack of "ordering" info in this case, it *
* would often discover the second or third move in the list had not *
* been played very often and cull the rest of the list thinking it *
* was ordered by the number of times it was played. New channel=n *
* command works with old whisper command, but takes what Crafty *
* would normally whisper and directs it to channel "n" instead. *
* Primarily used with custom interface when observing a game on a *
* server. This lets other observers either listen or ignore the *
* analysis Crafty produces by using +chan n or -chan n. This code *
* contains all of Frank's xboard patches so that analyze mode and *
* so forth works cleanly. A new book random option <5> modifies *
* the probability of playing a move by letting the popularity of a *
* move affect the learned-value sorting algorithm somewhat. Minor *
* adjustment in pawn ram asymmetric term to simply count rams and *
* not be too concerned about which half of the board they are on. *
* adjustment to weak pawn code. Also increased bonus for king *
* tropism to attract pieces toward enemy king to improve attacking. *
* code that detects drawn K+RP+wrong bishop had a bug in that on *
* occasion, the defending king might not be able to reach the *
* queening square before the opposing king blocks it out. This *
* would let some positions look like draws when they were not. King *
* safety now uses square(7-distance(piece,king)) as one multiplier *
* to really encourage pieces to get closer to the king. In cases *
* whre one king is exposed, all pieces are attracted to that king *
* to attack or defend. This is turned off during the opening. *
* minor 50-move rule draw change to fix a bug, in that the game is *
* not necessarily a draw after 50 moves by both sides, because one *
* side might be mated by the 50th move by the other side. This *
* occurred in a game Crafty vs Ferret, and now works correctly. *
* *
* 11.15 Modified LearnBook() so that when Crafty terminates, or resigns, *
* or sees a mate, it will force LearnBook() to execute the learning *
* analysis even if 10 moves have not been made sine leaving the *
* book. Crafty now trusts large positive evals less when learning *
* about an opening, since such evals are often the result of the *
* opponent's blunder, rather than a really good opening line. *
* second learning stage implemented. Crafty maintains a permanent *
* hash file that it uses to store positions where the search value *
* (at the root of the tree) suddenly drop, and then it "seeds" the *
* real transposition table with these values at the start of each *
* of each search so that information is available earlier the next *
* time this game is played. Position.bin has the raw binary data *
* this uses, while position.lrn has the "importable" data. New *
* import <filename> [clear] command imports all learning data now, *
* eliminating the old book learn command. LearnFunction() modified *
* to handle "trusted" values (negative scores, because we are sure *
* that Crafty won't make an outright blunder very often) and *
* "untrusted" values (positive values often caused by the opponent *
* hanging a piece. Trusted values are scaled up if the opponent is *
* weaker than Crafty since a weaker opponent forcing a negative *
* eval means the position must really be bad, and are scaled down *
* somewhat if the opponent is stronger than Crafty (from the rating *
* information from ICC or the operator using the rating command.) *
* Untrusted values are scaled down harshly, unless the opponent is *
* much stronger than Crafty, since it is unlikely such an opponent *
* would really blunder, while weaker opponents drastically scale *
* untrusted value (which is positive, remember) down. minor depth *
* problem fixed in learning code. The depth used in LearnFunction *
* was not the depth for the search that produced the "learn value" *
* the LearnBook() chooses, it was the depth for the search last *
* done. Now, in addition to the 10 last search values, I store the *
* depth for each as well. When a particular search value is used *
* to "learn", the corresponding (correct) depth is also now used. *
* These learn values are now limited to +6000/-6000 because in one *
* book line, Crafty discovered it was getting mated in 2 moves at *
* the end of the book line which was 30 moves deep. If you try to *
* distribute a "mate score" as the learned value, it will instantly *
* make every move for the last 26 moves look too bad to play. This *
* is not desirable, rather the last few moves should be unplayable, *
* but other moves further back should be o.k. Another bug that let *
* Crafty overlook the above mate also fixed. The search value was *
* not correct if Crafty got mated, which would avoid learning in *
* that case. This has been fixed, although it was obviously a rare *
* problem anyway. Minor draw bug fixed, where Crafty would offer *
* a draw when time was way low, caused by the resolution change a *
* few months back, and also it would offer a draw after the *
* opponent moved, even if he made a blunder. It now only offers a *
* draw after moving to make sure it's reasonable. Crafty now won't *
* resign if there is a deep mate, such as a mate in 10+, because we *
* want to be sure that the opponent can demonstrate making progress *
* before we toss in the towel. LearnBook() now learns on all games *
* played. The old algorithm had a serious problem in that negative *
* scores were trusted fully, positive scores were treated with low *
* confidence, and scores near zero were ignored totally. The net *
* result was that learning values became more and more negative as *
* games were played. Now equal positions are also factored in to *
* the learning equation to help pull some of these negative values *
* back up. Book() now excludes moves that have not been played *
* many times (if there is at least one move that has) for book *
* random = 2, 3 and 4. This stops some of the silly moves. *
* position learning is turned off after 15 moves have passed since *
* leaving book, to avoid learning things that won't be useful at a *
* later time. Hashing changed slightly to include "permanent" *
* entries so that the learned stuff can be copied into the hash *
* table with some confidence that it will stay there long enough to *
* be used. *
* *
* 11.16 King tropism toned down a little to not be quite so intent on *
* closeness to the kings, so that other positional ideas don't get *
* "lost" in the eval. Back to normal piece values (1,3,3,5,9) for *
* a while. Optimizations in Quiesce() speeded things up about 2%. *
* Pawns pushed toward the king are not so valuable any more so that *
* Crafty won't prefer to hold on to them rather than trading to *
* open a file(s) on the enemy king. BookLearn() call was moved in *
* Resign() so that it first learns, then resigns, so that it won't *
* get zapped by a SIGTERM right in the middle of learning when *
* xboard realizes the game is over. Edit/setboard logic modified *
* so that it is now possible to back up, and move forward in a game *
* that was set up via these commands. *
* *
* 11.17 EvaluatePawns() modified to eliminate "loose pawn" penalty which *
* was not particularly effective and produced pawn scores that were *
* sometimes misleading. Several optimizations dealing with cache *
* efficiency, primarily changing int's to signed char's so that *
* multiple values fit into a cache line together, to eliminate some *
* cache thrashing. PopCnt() no longer used to recognize that we *
* have reached an endgame database, there's now a counter for the *
* total number of pieces on the board, as it's much faster to inc *
* and dec that value rather than count 1 bits. Tweaks to MakeMove *
* and UnmakeMove to make things a couple of percent faster, but a *
* whole lot cleaner. Ditto for Swap and Quiesce. More speed, and *
* cleaner code. Outside passed pawn scored scaled down except when *
* the opponent has no pieces at all. "Lazy eval" cleaned up. We *
* now have two early exits, one before king safety and one after *
* king safety. There are two saved values so we have an idea of *
* how large the positional scores have gotten to make this work. *
* Bug in passed pawn code was evaluating black passed pawns as less *
* valuable than white. Fixed and passed pawn scores increased *
* slightly. Isolated pawn scoring modified so the penalty is pro- *
* portional to the number of isolani each side has, rather than the *
* old approach of penalizing the "excess" isolani one side has over *
* the other side. Seems to be more accurate, but we'll see. Fixed *
* a rather gross bug in ValidateMove() related to the way castling *
* status not only indicates whether castling is legal or not, but *
* if it's not, whether that side castled or move the king/rooks. *
* this let ValidateMove() fail to correctly detect that a castling *
* move from the hash table might be invalid, which could wreck the *
* search easily. This was an oversight from the new status code. *
* Serious book bug fixed. BookUp() was not counting wins and *
* losses correctly, a bug introduced to make small.pgn work. Minor *
* bug in the "trapped bishop" (a2/h2/a7/h7) code fixed. Minor bug *
* in Swap() also fixed (early exit that was not safe in rare cases.)*
* *
* 11.18 EvaluatePawns() modified to recognize that if there are two white *
* pawns "rammed" by black pawns at (say) c4/c5 and e4/e5, then any *
* pawns on the d-file are also effectively rammed as well since *
* there is no hope for advancing it. Auto232 automatic play code *
* seems to be working, finally. The problem was Crafty delayed *
* echoing the move back to auto232, if the predicted move was the *
* move played by the opponent. Auto232 gave Crafty 3 seconds and *
* then said "too late, you must be hung." Outpost knight scoring *
* modified to produce scores between 0 and .2 pawns. A knight was *
* getting too valuable, which caused some confusion in the scoring. *
* *
* 11.19 Slight reduction in the value of passed pawns, as they were *
* getting pretty large. Cleaned up annotate.c to get rid of code *
* that didn't work out. Annotate now gives the PV for the move *
* actually played as well as the move Crafty suggests is best. *
* Crafty now has a reasonable "trade" bonus that kicks in when it *
* has 20 points of material (or less) and is ahead or behind at *
* least 2 pawns. This trade bonus ranges from 0 to 1000 (one pawn) *
* and encourages the side that is winning to trade, while the side *
* that is losing is encouraged to avoid trades. More minor tweaks *
* for auto232 including trying a delay of 100ms before sending *
* a move. New annotate command gives the option to get more than *
* one suggested best move displayed, as well as fixes a few bugs *
* in the older code. Fix to bishop + wrong rook pawn code to also *
* recognize the RP + no pieces is just as bad if the king can reach *
* the queening square first. *
* *
* 11.20 Cleanup to annotate command. It now won't predict that one side *
* will follow a book line that only resulted in losses. Also a *
* couple of glitches in annotate where it was possible for a move *
* to take an exhorbitant amount of time if the best move was a *
* book move, but there were no other possible book moves. The *
* trade bonus now includes trade pawns if behind, but not if ahead *
* as well as now considering being ahead or behind only one pawn *
* rather than the two pawns used previously in 11.19. *
* *
* 11.21 Additional bug fix in annotate command that would fail if there *
* was only one legal move to search. Passed pawn values now have *
* an added evaluation component based on material on the board, so *
* that they become more valuable as material is traded. *
* *
* 11.22 Test command modified. Test <filename> [N] (where N is optional *
* and defaults to 99) will terminate a test position after N con- *
* secutive iterations have had the correct solution. Bug in *
* Quiesce() fixed, which would incorrectly prune (or fail to prune) *
* some captures, due to using "Material" which is computed with *
* respect to white-to-move. This was fixed many versions ago, but *
* the fix was somehow lost. Fix to EvaluateDraws that mistakenly *
* declared some endings drawn when there were rookpawns on both *
* sides of the board, and the king could get in front of one. Minor *
* fix to RepetitionCheck() that was checking one too many entries. *
* No harmful effect other than one extra iteration in the loop that *
* would make "purify/purity" fail as well as slow things down 1% or *
* so. *
* *
* 11.23 logpath=, bookpath= and tbpath= command line options added to *
* direct logs, books and tb files to the indicated path. These *
* only work as command line options, and can't be used in normal *
* places since the files are already opened and in use. A bug in *
* Evaluate() would call EvaluatePawns() when there were no pawns, *
* breaking things on many systems. *
* *
* 12.0 Rewrite of Input/Output routines. Crafty no longer relies on the *
* C library buffered I/O routine scanf() for input. This made it *
* basically impossible to determine when to read data from the key- *
* board, which made xboard/winboard difficult to interface with. *
* Now Crafty does its own I/O using read(), which is actually much *
* cleaner and easier. Minor bug where a fail high in very short *
* time controls might not get played... *
* *
* 12.1 Clean-up of Main(). The code had gotten so obtuse with the *
* pondering call, plus handling Option() plus move input, that it *
* was nearly impossible to follow. It is now *much* cleaner and *
* easier to understand/follow. *
* *
* 12.2 Continued cleanup of I/O, particularly the way main() is *
* structured, to make it more understandable. Rewritten time.c *
* to make it more readable and understandable, not to mention *
* easier to modify. Fixed a timing problem where Crafty could be *
* pondering, and the predicted move is made followed immediately by *
* "force", caused when the opponent makes a move and loses on time, *
* or makes a move and resigns. This would leave the engine state *
* somewhat confused, and would result in the "new" command not *
* reinitializing things at all, which would hang Crafty on xboard *
* or winboard. *
* *
* 12.3 Modified piece values somewhat to increase their worth relative *
* to a pawn, to try to stop the tendency to sac a piece for 3 pawns *
* and get into trouble for doing so. Minor fixes in NewGame() that *
* caused odd problems, such as learning positions after 1. e4. The *
* position.lrn/.bin files were growing faster than they should. *
* Other minor tweaks to fix a few broken commands in Option(). *
* Slight reduction in trade bonus to match slightly less valuable *
* pawns. *
* *
* 12.4 Added ABSearch() macro, which makes Search() much easier to read *
* by doing the test to call Search() or Quiesce() in the macro *
* where it is hidden from sight. Bugs in the way the log files *
* were closed and then used caused crashed with log=off. *
* *
* 12.5 Development bonus for central pawns added to combat the h4/a3 *
* sort of openings that would get Crafty into trouble. It now will *
* try to seize the center if the opponent dallies around. *
* *
* 12.6 Bug in EvaluateDraws() that would erroneously decide that a KNP *
* vs K was drawn if the pawn was a rook pawn and the king could get *
* in front of it, which was wrong. Another minor bug would use *
* EvaluateMate() when only a simple exchange ahead, which would *
* result in sometimes giving up a pawn to reach such a position. *
* Minor bug in SetBoard() would incorrectly reset many important *
* game state variables if the initial position was set to anything *
* other than the normal starting position, such as wild 7. This *
* would make learning add odd PV's to the .lrn file. Development *
* bonus modified to penalize moving the queen before minor pieces, *
* and not moving minor pieces at all. It is now possible to build *
* a "wild 7" book, by first typing "wild 7", and then typing the *
* normal book create command. Crafty will remember to reset to the *
* "wild 7" position at the start of each book line. Note that it *
* is not possible to have both wild 7 book lines *and* regular book *
* lines in the same book. *
* *
* 12.7 Failsoft added, so that scores can now be returned outside the *
* alpha/beta window. Minor null-move threat detection added where *
* a mate in 1 score, returned by a null-move search, causes a one *
* ply search extension, since a mate in one is a serious threat. *
* razoring is now disabled if there is *any* sort of extension in *
* the search preceeding the point where razoring would be applied, *
* to avoid razoring taking away one ply from a search that was ex- *
* tended (for good reasons) earlier. Fail-soft discarded, due to *
* no advantages at all, and a slight slowdown in speed. Rewrite of *
* pawn hashing, plus a rewrite of the weak pawn scoring code to *
* make it significantly more accurate, while going a little slower *
* (but since hashing hits 99% of the time, the slower speed is not *
* noticable at all.) Evaluation tweaking as well. *
* *
* 12.8 Continued work on weak pawn analysis, as well as a few minor *
* changes to clean the code up. *
* *
* 13.0 Preparation for the Paris WMCCC version starts here. First new *
* thing is the blocked pawn evaluation code. This recognizes when *
* a pawn is immobolized and when a pawn has lever potential, but *
* is disabled if playing a computer opponent. Passed pawn scoring *
* modified to eliminate duplicate bonuses that were added in *
* EvaluatePawns as well as EvaluatePassedPawns. Trade bonus code *
* rewritten to reflect trades made based on the material when the *
* search begins. This means that some things have to be cleared in *
* the hash table after a capture is really made on the board, but *
* prevents the eval from looking so odd near the end of a game. *
* minor bug with book random 0 fixed. If there was only one book *
* move, the search could blow up. *
* *
* 13.1 All positional scores reduced by 1/4, in an attempt to balance *
* things a little better. Also more modifications to the weak and *
* blocked pawn code. Added evaluation code to help with KRP vs KR, *
* so that the pawn won't be advanced too far before the king comes *
* to its aid. Ditto for defending, it knows that once the king is *
* in front of the pawn, it is a draw. *
* *
* 13.2 Blocked pawn scoring changed slightly to not check too far to see *
* if a pawn can advance. Also pawns on center squares are weighted *
* more heavily to encourage keeping them there, or trying to get *
* rid of them if the opponent has some there. Discovered that *
* somehow, the two lines of code that add in bonuses for passed *
* pawns were deleted as I cleaned up and moved code around. These *
* were reinserted (missing from 13.0 on). *
* *
* 13.3 Modified tablebase code to support 5 piece endings. There is now *
* a configuration option (see Makefile) to specify 3, 4 or 5 piece *
* endgame databases. More evaluation tuning. *
* *
* 13.4 Modified null-move search. If there is more than a rook left for *
* the side on move, null is always tried, as before. If there is *
* a rook or less left, the null move is only tried within 5 plies *
* of the leaf positions, so that as the search progresses deeper, *
* null-move errors are at least moved away from the root. Many *
* evaluation changes, particularly to king safety and evaluating *
* castling to one side while the other side is safer. Also it now *
* handles pre-castled positions better. *
* *
* 13.5 "From-to" display patch from Jason added. This shows the from *
* and to squares on a small diagram, oriented to whether Crafty is *
* playing black or white. The intent is to minimize operator *
* errors when playing black and the board coordinates are reversed. *
* More eval changes. *
* *
* 13.6 Weak pawns on open files now add value to the opponent's rooks *
* since they are the pieces that will primarily use an open file to *
* attack a weak pawn. *
* *
* 13.7 Minor eval tweaks, plus fixes for the CR/LF file reading problems *
* in windows NT. *
* *
* 13.8 Adjustments to book.c, primarily preventing Crafty from playing *
* lines that had very few games in the file, because those are *
* often quite weak players. Minor fix to InputMoves() so that a *
* move like bxc3 can *never* be interpreted as a bishop move. A *
* bishop move must use an uppercase B, as in Bxc3. Bug in the *
* king safety for white only was not checking for open opponent *
* files on the king correctly. *
* *
* 13.9 Minor adjustment to time allocation to allow "operator time" to *
* affect time per move. This is set by "operator <n>" where <n> is *
* time in seconds per move that should be "reserved" to allow the *
* operator some typing/bookkeeping time. New command "book *
* trigger <n>" added so that in tournament mode, when choosing a *
* book line, Crafty will revert to book random 0 if the least *
* popular move was played fewer times than <n>. This is an attempt *
* to avoid trusting narrow book lines too much while still allowing *
* adequate randomness. If the least frequently played move in the *
* set of book moves was played fewer times than this, then a search *
* over all the book moves is done. If the best one doesn't look *
* so hot, Crafty drops out of book and searches *all* legal moves *
* instead. *
* *
* 13.10 Minor adjustments. This is the gold Paris version that is going *
* with Jason. Any changes made during the event will be included *
* in the next version. *
* *
* 14.0 Major eval modification to return to centipawn evaluation, rather *
* then millipawns. This reduces the resolution, but makes it a lot *
* easier to understand evaluation changes. Significant eval mods *
* regarding king safety and large positional bonuses, where the ad- *
* vantage is not pretty solid. Note that old book learning will *
* not work now, since the evals are wrong. Old position learning *
* must be deleted completely. See the read.me file for details on *
* what must be done about book learning results. New egtb=n option *
* to replace the older -DTABLEBASES=n Makefile option, so that the *
* tablebases can be enabled or disabled without recompiling. *
* *
* 14.1 Glitch in EvaluateDevelopment() was producing some grossly large *
* positional scores. Also there were problems with where the *
* PreEvaluate() procedure were called, so that it could be called *
* *after* doing RootMoveslist(), but before starting a search. This*
* caused minor problems with hashing scores. One case was that it *
* was possible for a "test suite" to produce slightly different *
* scores than the same position run in normal mode. This has been *
* corrected. St=n command now supports fractional times to .01 *
* second resolution. *
* *
* 14.2 MATE reduced to 32767, which makes all scores now fit into 16 *
* bits. Added code to EvaluatePawns() to detect the Stonewall *
* pawn formation and not like it as black. Also it detects a *
* reversed Stonewall formation (for black) and doesn't like it as *
* white. EvaluateOutsidePassedPawns() removed. Functionality is *
* incorporated in EvaluatePawns() and is hashed, which speeds the *
* evaluation up a bit. King safety is now fully symmetric and is *
* folded into individual piece scoring to encourage pieces to *
* attack an unsafe king. *
* *
* 14.3 Minor adjustments to the king safety code for detecting attacks *
* initiated by pushing kingside pawns. Flip/flop commands added to *
* mirror the board either horizontally or vertically to check for *
* symmetry bugs in the evaluation. Other eval tuning changes. *
* *
* 14.4 Queen value increased to stop trading queen for two rooks. Book *
* learning slightly modified to react quicker. Also scores are now *
* stored in the book file as floats to get rid of an annoying trun- *
* cation problem that was dragging scores toward zero. The book *
* file now has a "version" so that old book versions won't cause *
* problems due to incorrect formats. Null-move mated threat ex- *
* tension was modified. If null-move search fails high, I fail *
* high as always, if it fails low, and it says I get mated in N *
* moves, I extend all moves at this ply, since something is going *
* on. I also carry this threat extension into the hash table since *
* a hash entry can say "don't do null move, it will fail low." I *
* now have a flag that says not only will null-move fail low, it *
* fails to "mated in N" so this ply needs extending even without a *
* null-move search to tell it so. Book learning greatly modified *
* in the way it "distributes" the learned values, in an effort to *
* make learning happen faster. I now construct a sort of "tree" *
* so I know how many book alternatives Crafty had at each move it *
* at each book move it played. I then assign the whole learn value *
* to all moves below the last book move where there was a choice, *
* and also assign the whole learn value to the move where there *
* was a choice. I then divide the learn value by the number of *
* choices and assign this to each book move (working backward once *
* again) until the next point where there were choices. This makes *
* sure that if there is a choice, and it is bad, it won't be played *
* again, even if this choice was at move 2, and the remainder of *
* the book line was completely forced. All in an effort to learn *
* more quickly. *
* *
* 14.5 annotate bug fixed where if there was only one legal move, the *
* annotation would stop with no warning. BookUp() now produces a *
* more useful error message, giving the exact line number in the *
* input file where the error occurred, to make fixing them easier. *
* If you are playing without a book.bin, 14.4 would crash in the *
* book learning code. This is now caught and avoided. BookUp() *
* now knows how to skip analysis in PGN files, so you can use such *
* files to create your opening book, without having problems. It *
* understands that nesting () {} characters "hides" the stuff in- *
* side them, as well as accepting non-standard PGN comments that *
* are inside []. Annotate() now will annotate a PGN file with *
* multiple games, although it will use the same options for all of *
* the games. PGN headers are preserved in the .can file. Annotate *
* now will recognize the first move in a comment (move) or {move} *
* and will search that move and give analysis for it in addition to *
* the normal output. *
* *
* 14.6 Minor change to book random 4 (use learned value.) if all the *
* learned values are 0, then use the book random 3 option instead. *
* Bug in 50-move counter fixed. Learn() could cause this to be set *
* to a value that didn't really reflect the 50-move status, and *
* cause games to be drawn when they should not be. Modified the *
* "Mercilous" attack code to recognize a new variation he worked *
* out that sacrifices a N, R and B for a mating attack. No more. *
* *
* 14.7 "Verbose" command removed and replaced by a new "display" command *
* that sets display options. Use "help display" for more info on *
* how this works. The "mercilous" attack scoring is only turned on *
* when playing "mercilous". But there is a new "special" list that *
* you can add players too if you want, and this special scoring is *
* turned on for them as well. *
* *
* 14.8 New scoring term to penalize unbalanced trades. IE if Crafty has *
* to lose a pawn, it would often trade a knight for two pawns in- *
* stead, which is actually worse. This new term prevents this sort *
* of trades. *
* *
* 14.9 "Mercilous" attack code modified to handle a new wrinkle he (and *
* one other player) found. *
* *
* 14.10 New "bench" command runs a test and gives a benchmark comparison *
* for Crafty and compares this to a P6/200 base machine. Minor bug *
* disabled the "dynamic draw score" and fixed it at zero, even if *
* the opponent was much weaker (rating) or behind on time. Also *
* draw_score was not reset to 0 at start of each new game, possibly *
* leaving it at +.20 after playing a higher-rated opponent. *
* *
* 14.11 Release to make mercilous attack detection code the default, to *
* prevent the rash of mercilous attacks on the chess servers. *
* *
* 14.12 Modified tuning of evaluation. Scores were reduced in the past, *
* to discourage the piece for two pawns sort of trades, but since *
* this was basically solved in 14.8, scores are going "back up". *
* Particularly passed pawn scores. Crafty now accepts draw offers *
* if the last search result was <= the current result returned by *
* DrawScore(). It also honors draw requests via xboard when *
* against a human opponent as well, and will flag the game as over. *
* Minor modification to annotate.c to display move numbers in the *
* PV's to match the PV output format used everywhere else in *
* Crafty. A new type of learning, based on results, has been added *
* and is optional (learn=7 now enables every type of learning.) *
* this type of learning uses the win/lose game result to flag an *
* opening that leads to a lost game as "never" play again. The *
* book move selection logic has been modified. There are four com- *
* ponents used in choosing book moves: frequency of play; win/lose *
* ratio; static evaluation; and learned score. There are four *
* weights that can be modified with the bookw command, that control *
* how these 4 values are used to choose book moves. Each weight is *
* a floating point value between 0 and 1, and controls how much the *
* corresponding term factors in to move selection. *
* *
* 14.13 Fixed a book parsing bug that now requires a [Site "xxx"] tag in *
* any book file between lines for the "minplay" option of book *
* create to work properly. *
* *
* 15.0 This is the first version to support a parallel search using *
* multiple processors on a shared-memory machinel. This version *
* uses the "PVS" algorithm (Principal Variation Search) that is an *
* early form of "Young Brothers Wait". This is not the final *
* search algorithm that will be used, but it is relatively easy to *
* implement, so that the massive data structure changes can be de- *
* bugged before getting too fancy. The major performance problem *
* with this approach is that all processors work together at a node *
* and when one finishes, it has to wait until all others finish *
* before it can start doing anything more. This adds up to a *
* significant amount of time and really prevents good speedups on *
* multiprocessor machines. This restriction will be eliminanted in *
* future versions, but it makes debugging much simpler for the *
* first version. After much agonizing, I finally chose to write my *
* own "spinlock" macros to avoid using the pthread_mutex_lock stuff *
* that is terribly inefficient due to its trying to be cute and *
* yield the processor rather than spinning, when the lock is al- *
* ready set. i'd rather spin than context-switch. *
* *
* 15.1 This version actually unleashes the full design of the parallel *
* search, which lets threads split away from the "pack" when *
* they become idle, and they may then jump in and help another *
* busy thread. This eliminates the significant delays that *
* occur near the end of a search at a given ply. Now as those pro- *
* cessors drop out of the search at that ply, they are reused at *
* other locations in the tree without any significant delays. *
* *
* 15.2 WinNT support added. Also fixed a small bug in Interrupt() that *
* could let it exit with "busy" set so that it would ignore all *
* input from that point forward, hanging the game up. Added a new *
* "draw accept" and "draw decline" option to enable/disable Crafty *
* accepting draw offers if it is even or behind. Turned on by *
* an IM/GM opponent automatically. Thread pools now being used to *
* avoid the overhead of creating/destroying threads at a high rate *
* rate of speed. It is now quite easy to keep N processors busy. *
* *
* 15.3 CPU time accounting modified to correctly measure the actual time *
* spent in a parallel search, as well as to modify the way Crafty *
* handles time management in an SMP environment. A couple of bugs *
* fixed in book.c, affecting which moves were played. Also veri- *
* fied that this version will play any ! move in books.bin, even if *
* it was not played in the games used to build the main book.bin *
* file. *
* *
* 15.4 This version will terminate threads once the root position is in *
* a database, to avoid burning cpu cycles that are not useful. A *
* flag "done" is part of each thread block now. When a thread goes *
* to select another move to search, and there are no more left, it *
* sets "done" in the parent task thread block so that no other pro- *
* cessors will attempt to "join the party" at that block since no *
* work remains to be done. Book selection logic modified so that *
* frequency data is "squared" to improve probabilities. Also, the *
* frequency data is used to cull moves, in that if a move was not *
* played 1/10th of the number of times that the "most popular" move *
* was played, then that move is eliminated from consideration. *
* *
* 15.5 Changes to "volatile" variables to enhance compiler optimization *
* in places where it is safe. Added a function ThreadStop() that *
* works better at stopping threads when a fail high condition *
* occurs at any nodes. It always stopped all sibling threads at *
* the node in question, but failed to stop threads that might be *
* working somewhere below the fail-high node. ThreadStop() will *
* recursively call itself to stop all of those threads. Significant *
* increase in king centralization (endgame) scoring to encourage *
* the king to come out and fight rather than stay back and get *
* squeezed to death. Minor change to queen/king tropism to only *
* conside the file distance, not ranks also. Bug in interupt.c *
* fixed. This bug would, on very rare occasion, let Crafty read in *
* a move, but another thread could read on top of this and lose the *
* move. Xboard would then watch the game end with a <flag>. *
* *
* 15.6 Ugly repetition draw bug (SMP only) fixed. I carefully copied *
* the repetition list from parent to child, but also copied the *
* repetition list pointer... which remained pointing at the parent *
* repetition list. Which failed, of course. *
* *
* 15.7 Problem in passing PV's back up the search fixed. The old bug of *
* a fail high/fail low was not completely handled, so that if the *
* *last* move on a search failed high, then low, the PV could be *
* broken or wrong, causing Crafty to make the wrong move, or else *
* break something when the bogus PV was used. Piece/square tables *
* now only have the _w version initialized in data.c, to eliminate *
* the second copy which often caused errors. Initialize() now will *
* copy the _w tables to the _b tables (reflected of course.) *
* *
* 15.8 trade bonus modified to not kick in until one side is two pawns *
* ahead or behind, so that trading toward a draw is not so common. *
* Fixed a whisper bug that would cause Crafty to whisper nonsense *
* if it left book, then got back in book. It also now whispers the *
* book move it played, rather than the move it would play if the *
* opponent played the expected book move, which was confusing. *
* *
* 15.9 Bug in positions with one legal move would abort the search after *
* a 4 ply search, as it should, but it was possible that the result *
* from the aborted search could be "kept" which would often make *
* Crafty just "sit and wait" and flag on a chess server. *
* *
* 15.10 Fixed "draw" command to reject draw offers if opponent has < ten *
* seconds left and no increment is being used. Fixed glitch in *
* LearnResult() that would crash Crafty if no book was being used, *
* and it decides to resign. Modified trade bonus code to eliminate *
* a hashing inconsistency. Minor glitch in "show thinking" would *
* show bad value if score was mate. Added Tim Mann's new xboard/ *
* winboard "result" command and modified the output from Crafty to *
* tell xboard when a game is over, using the new result format that *
* Tim now expects. Note that this is xboard 3.6.9, and earlier *
* versions will *not* work correctly (ok on servers, but not when *
* you play yourself) as the game won't end correctly due to the *
* change in game-end message format between the engine and xboard. *
* *
* 15.11 Modified SMP code to not start a parallel search at a node until *
* "N" (N=2 at present) moves have been search. N was 1, and when *
* move ordering breaks down the size of the tree gets larger. This *
* controls that much better. Fixed an ugly learning bug. If the *
* last move actually in the game history was legal for the other *
* side, after playing it for the correct side, it could be played *
* a second time, which would break things after learning was done. *
* An example was Rxd4 for white, where black can respond with Rxd4. *
* Changes for the new 3.6.10 xboard/winboard are also included as *
* well as a fix to get book moves displayed in analysis window as *
* it used to be done. *
* *
* 15.12 "The" SMP repetition bug was finally found and fixed. CopyToSMP *
* was setting the thread-specific rephead_* variable *wrong* which *
* broke so many things it was not funny. Evaluation tuning in this *
* version as well to try to "center" values in a range of -X to +X *
* rather than 0 to 2X. Trade bonus had a bug in the pawn part that *
* not only encouraged trading pawns when it should be doing the *
* opposite, but the way it was written actually made it look bad to *
* win a pawn. More minor xboard/winboard compatibility bugs fixed *
* so that games end when they should. DrawScore() had a quirk that *
* caused some problems, in that it didn't know what to do with non- *
* zero draw scores, and could return a value with the wrong sign at *
* times. It is now passed a flag, "Crafty_is_white" to fix this. *
* Modification so that Crafty can handle the "FEN" PGN tag and set *
* the board to the correct position when it is found. Xboard *
* options "hard" and "easy" now enable and disable pondering. *
* *
* 15.13 Modification to "bad trade" code to avoid any sort of unbalanced *
* trades, like knight/bishop for 2-3 pawns, or two pieces for a *
* rook and pawn. More new xboard/winboard fixes for Illegal move *
* messages and other engine interface changes made recently. Minor *
* change to null move search, to always search with the alpha/beta *
* window of (beta-1,beta) rather than (alpha,beta), which is very *
* slightly more efficient. *
* *
* 15.14 Rewrite of ReadPGN() to correctly handle nesting of various sorts *
* of comments. This will now correctly parse wall.pgn, except for *
* promotion moves with no promotion piece specified. The book *
* create code also now correctly reports when you run out of disk *
* space and this should work under any system to let you know when *
* you run out of space. *
* *
* 15.15 Major modifications to Book() and BookUp(). BookUp() now needs *
* 1/2 the temp space to build a book that it used to need (even *
* less under windows). Also, a book position is now 16 bytes in- *
* stead of 20 (or 24 under windows) further reducing the space *
* requirements. The "win/lose/draw" counts are no longer absolute, *
* rather they are relative so they can be stored in one byte. A new *
* method for setting "!" moves in books.bin is included in this *
* version. For any move in the input file used to make books.bin, *
* you can add a {play nn%} string, which says to play this move nn% *
* of the time, regardless of how frequently it was played in the *
* big book file. For example, e4 {play 50%} says to play e4 50% of *
* the time. Note two things here: (1) If the percentages for all *
* of white's first moves add up to a number > 100, then the *
* percentage played is taken as is, but all will be treated as if *
* they sum to 100 (ie if there are three first moves, each with a *
* percentage of 50%, they will behave as though they are all 33% *
* moves). (2) For any moves not marked with a % (assuming at least *
* one move *is* marked with a percent) then such moves will use the *
* remaining percentage left over applied to them equally. Note that *
* using the % *and* the ! flags together slightly changes things, *
* because normally only the set of ! moves will be considered, and *
* within that set, any with % specified will have that percent used *
* as expected. But if you have some moves with !, then a percent *
* on any of the *other* moves won't do a thing, because only the ! *
* moves will be included in the set to choose from. *
* *
* 15.16 Bug in the king tropism code, particularly for white pieces that *
* want to be close to the black king, fixed in this version. New *
* History() function that handles all history/killer cases, rather *
* than the old 2-function approach. Ugly RepetitionCheck() bug *
* fixed in CopyToSMP(). This was not copying the complete replist *
* due to a ply>>2 rather than ply>>1 counter. *
* *
* 15.17 Adjustments to "aggressiveness" to slightly tone it down. Minor *
* fix to avoid the odd case of whispering one move and playing an- *
* other, caused by a fail-high/fail-low overwriting the pv[1] stuff *
* and then Iterate() printing that rather than pv[0] which is the *
* correct one. New LegalMove() function that strengthens the test *
* for legality at the root, so that it is impossible to ponder a *
* move that looks legal, but isn't. Modifications to king safety *
* to better handle half-open files around the king as well as open *
* files. EGTB "swindler" added. If the position is drawn at the *
* root of the tree, then all losing moves are excluded from the *
* move list and the remainder are searched normally with the EGTB *
* databases disabled, in an effort to give the opponent a chance to *
* go wrong and lose. Fixed "mode tournament" and "book random 0" *
* so that they will work correctly with xboard/winboard, and can *
* even be used to play bullet games on a server if desired. Minor *
* fix to attempt to work around a non-standard I/O problem on the *
* Macintosh platform dealing with '\r' as a record terminator *
* rather than the industry/POSIX-standard \n terminator character. *
* *
* 15.18 Fix to the "material balance" evaluation term so that it will not *
* like two pieces for a rook (plus pawn) nor will it like trading a *
* piece for multiple pawns. A rather gross bug in the repetition *
* code (dealing with 50 move rule) could overwrite random places in *
* memory when the 50 move rule approached, because the arrays were *
* not long enough to hold 50 moves, plus allow the search to go *
* beyond the 50-move rule (which is legal and optional) and then *
* output moves (which uses ply=65 data structures). This let the *
* repetition (50-move-rule part) overwrite things by storing well *
* beyond the end of the repetition list for either side. Minor fix *
* to EGTB "swindle" code. It now only tries the searches if it is *
* the side with swindling chances. Ie it is pointless to try for *
* a swindle in KRP vs KR if you don't have the P. :) Some very *
* substantial changes to evaluate.c to get things back into some *
* form of synch with each other. *
* *
* 15.19 More evaluation changes. Slight change to the Lock() facility *
* as it is used to lock the hash table. Modifications to the book *
* selection logic so that any move in books.bin that is not in the *
* regular book.bin file still can be played, and will be played if *
* it has a {play xxx%} or ! option. New option added to the book *
* create command to allow the creation of a better book. This *
* option lets you specify a percentage that says "exclude a book *
* move it if didn't win xx% as many games as it lost. IE, if the *
* book move has 100 losses, and you use 50% for the new option, the *
* move will only be included if there are at least 50 wins. This *
* allows culling lines that only lost, for example. New bad trade *
* scoring that is simpler. If one side has one extra minor piece *
* and major pieces are equal, the other side has traded a minor for *
* pawns and made a mistake. If major pieces are not matched, and *
* one side has two or more extra minors, we have seen either a rook *
* for two minor pieces (bad) or a queen for three minor pieces (bad *
* also). Horrible bug in initializing min_thread_depth, which is *
* supposed to control thrashing. The SMP search won't split the *
* tree within "min_thread_depth" of the leaf positions. Due to a *
* gross bug, however, this was initialized to "2", and would have *
* been the right value except that a ply in Crafty is 4. The *
* mtmin command that adjusts this correctly multiplied it by 4, *
* but in data.c, it was left at "2" which lets the search split way *
* too deeply and can cause thrashing. It now correctly defaults to *
* 120 (2*PLY) as planned. Crafty now *only* supports *
* winboard/xboard 4.0 or higher, by sending the string "move xxx" *
* to indicate its move. This was done to eliminate older xboard *
* versions that had some incompatibilities with Crafty that were *
* causing lots of questions/problems. Xboard 4.0 works perfectly *
* and is the only recommended GUI now. *
* *
* 15.20 New evaluation term to ensure that pawns are put on squares of *
* the opposite color as the bishop in endings where one side only *
* has a single bishop. Another new evaluation term to favor *
* bishops over knights in endings with pawns on both sides of the *
* board. Search extensions now constrained so that when doing an *
* N-ply search, the first 2N plies can extend normally, but beyond *
* that the extensions are reduced by one-half. This eliminates a *
* few tree explosions that wasted lots of time but didn't produce *
* any useful results. This version solves 299/300 of the Win at *
* Chess positions on a single-cpu pentium pro 200mhz machine now. *
* New evaluation term to reward "pawn duos" (two pawns side by side *
* which gives them the most flexibility in advancing. A change to *
* the bishops of opposite color to not just consider B vs B drawish *
* when the B's are on opposite colors, but to also consider other *
* positons like RB vs RB drawish with opposite B's. *
* *
* 16.0 Hash functions renamed to HashProbe() and HashStore(). The store *
* functions (2) were combined to eliminate some duplicate code and *
* shrink the cache footprint a bit. Adjustment to "losing the *
* right to castle" so that the penalty is much less if this is done *
* when trading queens, since a king in the center becomes less of a *
* problem there. Several eval tweaks. Support for Eugene Nalimov's *
* new endgame databases that reduce the size by 50%. Added a new *
* cache=xxx command to set the tablebase cache (more memory means *
* less I/O of course). The "egtb" command now has two uses. If *
* use egtb=0, you can disable tablebases for testing. Otherwise, *
* you just add "egtb" to your command line or .craftyrc file and *
* Crafty automatically recognizes the files that are present and *
* sets up to probe them properly. Added an eval term to catch a *
* closed position with pawns at e4/d3/c4 and then avoiding the *
* temptation to castle into an attack. Most of the evaluation *
* discontinuities have been removed, using the two new macros *
* ScaleToMaterial() and InverseScaleToMaterial(). Scale() is used *
* to reduce scores as material is removed from the board, while *
* InverseScale() is used to increase the score as material is *
* removed. This removed a few ugly effects of things happening *
* right around the EG_MAT threshold. *
* *
* 16.1 Bug in EGTBProbe() which used the wrong variable to access the *
* enpassant target square was fixed. The cache=x command now *
* checks for a failed malloc() and reverts to the default cache *
* size to avoid crashes. Major eval tuning changes. Cache bug *
* would do an extra malloc() and if it is done after the "egtb" *
* command it would crash. Analyze mode now turns off the "swindle" *
* mode. *
* *
* 16.2 More evaluation changes, specifically to bring king safety down *
* to reasonable levels. Support for the DGT electronic chess board *
* is now included (but only works in text mode, not in conjunction *
* with xboard/winboard yet. Fix to HashStore() that corrected a *
* problem with moving an entry from tablea to tableb, but to the *
* wrong address 50% of the time (thanks to J. Wesley Cleveland). *
* *
* 16.3 Performance tweaks plus a few evaluation changes. An oversight *
* would let Crafty play a move like exd5 when cxd5 was playable. *
* IE it didn't follow the general rule "capture toward the center." *
* this has been fixed. King safety ramped up just a bit. *
* *
* 16.4 Search extension fixed. One-reply was being triggered when there *
* was only one capture to look at as well, which was wrong. Minor *
* fix to king safety in Evaluate(). Adjustments to preeval to fix *
* some "space" problems caused by not wanting to advance pawns at *
* all, plus some piece/square pawn values that were too large near *
* the opponent's king position. New swindle on*off command allows *
* the user to disable "swindle mode" so that Crafty will report *
* tablebase draws as draws. Swindle mode is now disabled auto- *
* matically in analysis or annotate modes. DrawScore() now returns *
* a draw score that is not nearly so negative when playing humans. *
* The score was a bit large (-.66 and -.33) so that this could tend *
* to force Crafty into losing rather than drawn positions at times. *
* EGTB probe code now monitors how the probes are affecting the nps *
* and modifies the probe depth to control this. IE it adjusts the *
* max depth of probes to attempt to keep the NPS at around 50% or *
* thereabouts of the nominal NPS rate. Fixed a nasty bug in the *
* EGTB 'throttle' code. It was possible that the EGTB_mindepth *
* could get set to something more than 4 plies, then the next *
* search starts off already in a tablebase ending, but with this *
* probe limit, it wouldn't probe yet Iterate() would terminate the *
* search after a couple of plies. And the move chosen could draw. *
* New code submitted by George Barrett, which adds a new command *
* "html on". Using this will cause the annotate command to produce *
* a game.html file (rather than game.can) which includes nice board *
* displays (bitmapped images) everywhere Crafty suggests a different*
* move. You will need to download the bitmaps directory files to *
* make this work. Note that html on enables this or you will get *
* normal annotation output in the .can file. Final hashing changes *
* made. Now crafty has only two hash tables, the 'depth preferred' *
* and 'always store' tables, but not one for each side. *
* *
* 16.5 Minor glitch in internal iterative deepening code (in search.c) *
* could sometimes produce an invalid move. Crafty now probes the *
* hash table to find the best move which works in all cases. *
* Interesting tablebase bug fixed. By probing at ply=2, the *
* search could overlook a repetition/50 move draw, and turn a won *
* position into a draw. Crafty now only probes at ply > 2, to *
* let the RepetitionCheck() function have a chance. Added code by *
* Dan Corbett to add environment variables for the tablebases, *
* books, logfiles and the .craftyrc file paths. The environment *
* variables CRAFTY_TB_PATH, CRAFTY_BOOK_PATH, CRAFTY_LOG_PATH and *
* CRAFTY_RC_PATH should point to where these files are located and *
* offer an alternative to specifying them on the command line. *
* Final version of the EGTB code is included in this version. This *
* allows Crafty to use either compressed (using Andrew Kadatch's *
* compressor, _not_ zip or gzip) or non-compressed tablebases. It *
* will use non-compressed files when available, and will also use *
* compressed files that are available so long as there is no non- *
* compressed version of the same file. It is allowable to mix and *
* match as you see fit, but with all of the files compressed, the *
* savings is tremendous, roughly a factor of 5 in space reduction. *
* *
* 16.6 Major rewrite of king-safety pawn shelter code to emphasize open *
* files (and half-open files) moreso than just pawns that have been *
* moved. Dynamic EGTB probe depth removed. This caused far too *
* many search inconsistencies. A fairly serious SMP bug that could *
* produce a few hash glitches was found. Rewrite of the 'king- *
* tropism' code completed. Now the pieces that are 'crowding' the *
* king get a bigger bonus if there are more of them. Ie it is more *
* than twice as good if we have two pieces close to the king, while *
* before this was purely 'linear'. Minor fix to book.c to cure an *
* annotate command bug that would produce odd output in multi-game *
* PGN files. *
* *
* 16.7 Minor bug in 'book create' command would produce wrong line num- *
* bers if you used two book create commands without restarting *
* Crafty between uses. Replaced "ls" command with a !cmd shell *
* escape to allow _any_ command to be executed by a shell. Change *
* to bishop scoring to avoid a bonus for a bishop pair _and_ a good *
* bishop sitting at g2/g7/etc to fill a pawn hole. If the bishop *
* fills that hole, the bishop pair score is reduced by 1/2 to avoid *
* scores getting too large. Another ugly SMP bug fixed. It was *
* for the CopyFromSMP() function to fail because Search() put the *
* _wrong_ value into tree->value. The "don't castle into an unsafe *
* king position" code was scaled up a bit as it wasn't quite up to *
* detecting all cases of this problem. The parallel search has *
* been modified so that it can now split the tree at the root, as *
* well as at deeper nodes. This has improved the parallel search *
* efficiency noticably while also making the code a bit more *
* complex. This uses an an adaptive algorithm that pays close *
* attention to the node count for each root move. If one (or more) *
* moves below the best move have high node counts (indicating that *
* these moves might become new 'best' moves) then these moves are *
* flagged as "don't search in parallel" so that all such moves are *
* searched one by one, using all processors so that a new best move *
* if found faster. Positional scores were scaled back 50% and the *
* king safety code was again modified to incorporate pawn storms, *
* which was intentionally ignored in the last major revision. Many *
* other scoring terms have been modified as well to attempt to *
* bring the scores back closer to something reasonable. *
* *
* 16.8 Bug in evaluate.c (improper editing) broke the scoring for white *
* rooks on open files (among other things.) new twist on null- *
* move search... Crafty now uses R=3 near the root of the tree, *
* and R=2 near the top. It also uses null-move so long as there is *
* a single piece on the board, but when material drops to a rook or *
* less, null move is turned off and only used in the last 7 plies *
* to push the zugzwang errors far enough off that they can be *
* avoided, hopefully. *
* *
* 16.9 Tuning to king safety. King in center of board was way too high *
* which made the bonus for castling way too big. More fine-tuning *
* on the new 'tropism' code (that tries to coordinate piece attacks *
* on the king). It understands closeness and (now) open files for *
* the rooks/queens. Modified blocked center pawn code so that an *
* 'outpost' in front of an unmoved D/E pawn is made even stronger *
* since it restrains that pawn and cramps the opponent. *
* *
* 16.10 All scores are back to 16.6 values except for king safety, as *
* these values played well. King safety is quite a bit different *
* and now has two fine-tuning paramaters that can be set in the *
* crafty.rc file (try help ksafety for more details, or see the new *
* crafty.doc for more details. Suffice it to say that you can now *
* tune it to be aggressive or passive as you wish. *
* *
* 16.11 Adjustment to king safety asymmetry to make Crafty a bit more *
* cautious about starting a king-side attack. New "ksafe tropism" *
* command allows the tropism scores (pulling pieces toward opponent *
* king) to be adjusted up or down (up is more aggressive). *
* *
* 16.12 evaluation adjustment options changed. The new command to modify *
* this stuff is "evaluation option value". For example, to change *
* the asymmetry scoring for king safety, you now use "evaluation *
* asymmetry 120". See "help evaluation" for more details. There *
* is a new "bscale" option to adjust the scores for 'blocked' type *
* positions, and I added a new "blockers_list" so that players that *
* continually try to lock things up to get easy draws can be better *
* handled automatically. The command is "list B +name". There are *
* other adjustable evaluation scaling parameters now (again, use *
* "help evaluation" to see the options.) *
* *
* 16.13 Bug in Evaluate() fixed. King safety could produce impossibly *
* large scores due to negative subscript values. Minor change to *
* root.c to allow partial tablebase sets while avoiding the ugly *
* potential draw problem. This was supplied by Tim Hoooebeek and *
* seems to work ok for those wanting to have files like kpk with- *
* out the corresponding promotion files. *
* *
* 16.14 Bug in Evaluate() fixed. King safety could produce impossibly *
* large scores due to a subscript two (2) larger than expected for *
* max values. A couple of other minor tweaks to rook on 7th as *
* well. Setboard now validates enpassant target square to be sure *
* that an enpassant capture is physically possible, and that the *
* target square is on the right rank with pawns in the right place. *
* *
* 16.15 Bug in EGTBProbe() usage fixed. It was possible to call this *
* function before tablebases were initialized, or when there were *
* more than 3 pieces on one side, which would break a subscript. *
* *
* 16.16 Changes to the way EvaluatePassedPawn() works. It now does a *
* reasonable job of penalizing blockaded passed pawns. Also a bug *
* in king scoring used a variable set from the previous call to the *
* Evaluate() procedure, which could produce bizarre effects. A few *
* minor eval glitches that caused asymmetric scores unintentionally *
* were removed. *
* *
* 16.17 Minor "hole" in SMP code fixed. It was possible that a move *
* displayed as the best in Output() would not get played. *
* Very subtle timing issue dealing with the search timing out and *
* forgetting to copy the best move back to the right data area. *
* Minor fixes to the modified -USE_ATTACK_FUNCTIONS option that *
* was broken when the And()/Or()/ShiftX() macros were replaced by *
* their direct bitwise operator replacements. *
* *
* 16.18 Adjustments to king tropism scoring terms (these attract pieces *
* toward the opponent king in a coordinated way). The scoring term *
* that kept the queen from going to the opposite side of the board *
* was not working well which would also cause attacking problems. *
* Razoring code has been disabled, as it neither helps or hurts on *
* tactical tests, and it creates a few hashing problems that are *
* annoying. Bug in HashStorePV() that would store the PV into the *
* hash table, but possibly in the wrong table entry, which could *
* stuff a bad move in a hash entry, or overwrite a key entry that *
* could have been useful later. Book random 0 was slightly wrong *
* as it could not ignore book moves if the search said that the *
* score was bad. Also the search would not time-out properly on a *
* forced move, it would use the entire time alotted which was a big *
* waste of time when there was only one legal move to make. A very *
* interesting bug was found in storing mate bounds in the hash *
* table, one I had not heard of before. I now store two MATE *
* bounds, either > MATE-300, or < -MATE+300, which is conservative *
* but safe. Another change to Iterate() to make it avoid exiting *
* as soon as a mate is found, so that it can find the shortest mate *
* possible. *
* *
* 16.19 Savepos now pads each rank to 8 characters so that programs that *
* don't handle abbreviated FEN will be able to parse Crafty's FEN *
* output without problems. Threads are no longer started and *
* stopped before after searches that seem to not need multiple *
* threads (such as when the starting position is in the databases *
* or whatever) because in fast games, it can start and stop them *
* after each search, due to puzzling for a ponder move, and this is *
* simply to inefficient to deal with, and burning the extra cpus is *
* only bad if the machine is used for other purposes. And when the *
* machine is not dedicated to chess only, the SMP search is very *
* poor anyway. New lockless hashing (written by Tim Mann) added *
* to improve SMP performance. New eval term that handles various *
* types of candidate passed pawns, most commonly the result of a *
* position where one side has an offside majority that later turns *
* into an outside passed pawn. New EGTBPV() procedure added. This *
* code will print the entire PV of a tablebase mating line. If it *
* given an option of ! (command is "egtb !") it will add a ! to any *
* move where there is only one optimal choice. Crafty will now *
* automatically display the EGTB PV if you give it a setboard FEN *
* command, or if you just give it a raw FEN string (the setboard *
* command is now optional except in test suites). This version now *
* supports the 6 piece database files. To include this support, *
* you need to -DEGTB6 when compiling everything. The majority code *
* has been temporarily removed so that this version can be released *
* to get the 6 piece ending stuff out. *
* *
* 17.0 Connected passed pawn scoring modified so that connected passers *
* don't get any sort of bonus, except for those cases where the *
* opponent has a rook or more. This will avoid liking positions *
* where Crafty has two connected passers on the d/e files, and the *
* opponent has passers on the b/g files. The split passers win if *
* all pieces are traded, while the connected passers are better *
* when pieces are present. A new scoring term evaluates the *
* "split" passers similar to outside passers, this at the request *
* (make that demand) of GM Roman Dzindzichashvili. Book() now finds *
* the most popular move as the move to ponder. This eliminated all *
* 'puzzling' searches which result in clearing the hash tables two *
* times for every book move, which can slow it down when a large *
* hash table is used. New book option for playing against computer *
* opponents was written for this version. Crafty now supports two *
* "books.bin" type files, books.bin and bookc.bin (the bookc create *
* command can be used to make bookc.bin). Bookc will only be used *
* when Crafty is playing a computer. This is supplied by xboard or *
* winboard when playing on a server, or can be included int the *
* crafty.rc/.craftyrc file when playing directly. Bookc.bin will *
* be used when playing a computer only, and should be used to avoid *
* unsound lines that are fine against humans, but not against other *
* computers. If you don't use a bookc.bin, it will use the normal *
* books.bin as always. If you use both, it will only use bookc.bin *
* in games that have been started and then given the 'computer' *
* command. Minor adjustment to EGTB probe code so that it will *
* always probe TBs at ply=2 (if the right number of pieces are on *
* the board) but won't probe beyond ply=2 unless the move at the *
* previous ply was a capture/promotion and the total pieces drops *
* into the proper range for TB probes. This makes the 6 piece *
* files far more efficient as before it would continuously probe *
* after reaching 6 piece endings, even if it didn't have the right *
* file. now after the capture that takes us to a 6 piece ending *
* we probe one time... and if there is no hit we don't probe at *
* the next node (or any successors) unless there is another capture *
* or promotion that might take us to a database we have. The book *
* (binary) format has once again been modified, meaning that to use *
* 16.20 and beyond the book.bin/books.bin files must be re-built *
* from the raw PGN input. This new format includes an entry for *
* the CAP project score, so that deep searches can be used to guide *
* opening book lines. A new weight (bookw CAP) controls how much *
* this affects book move ordering/selection. A new import command *
* will take the raw CAPS data and merge it into the book.bin after *
* the file has been built. Serious bug in SetBoard() would leave *
* old EP status set in test suites. This has been fixed. Outpost *
* knight code was modified so that a knight in a hole is good, a *
* knight in a hole supported by a pawn is better, supported by two *
* pawns is still better, and if the opponent has no knights or a *
* bishop that can attack this knight it is even better. The out- *
* post bonus for a bishop was removed. A pretty serious parallel *
* search bug surfaced. In non-parallel searches, Crafty _always_ *
* completed the current ply=1 move after the time limit is reached, *
* just to be sure that this move isn't going to become a new best *
* move. However, when parallel searching, this was broken, and at *
* the moment time runs out, the search would be stopped if the *
* parallel split was done at the root of the tree, which means that *
* where the search would normally find a new best move, it would *
* not. This has been fixed. New "store <val>" command can be used *
* to make "position learning" remember the current position and the *
* score (val) you supply. This is useful in analyze mode to move *
* into the game, then let Crafty know that the current position is *
* either lost or won (with a specific score). *
* *
* 17.1 Book structure fixed, since compilers can't quite agree on how *
* structures ought to be aligned, for reasons not clear to me. A *
* serious eval bug that could produce gross scores when one side *
* had two queens was fixed. *
* *
* 17.2 Isolated pawn scoring tweaked a bit, plus a couple of bugs in the *
* way EvaluateDevelopment() was called were fixed. *
* *
* 17.3 Passed pawn scores increased somewhat to improve endgame play. *
* *
* 17.4 Minor bug with "black" command (extra line from unknown origin) *
* would make "black" command fail to do anything. Minor tweaks to *
* passed pawn scoring again... And a slight performance improve- *
* ment in how EvaluateKingSafety() is called. Code for "bk" *
* from xboard was somehow lost. It now provides a book hint. *
* *
* 17.5 Rewrite of outside passed pawn/pawn majority code. It is now *
* much faster by using pre-computed bitmaps to recognize the right *
* patterns. *
* *
* 17.6 Minor fix in interupt.c, which screwed up handling some commands *
* while pondering. Minor fix to score for weak back rank. Score *
* was in units of 'defects' but should have been in units of *
* "centipawns". Minor bug in "drawn.c" could mis-classify some *
* positions as drawn when they were not. *
* *
* 17.7 Repair to DrawScore() logic to stop the occasional backward sign *
* that could create some funny-looking scores (-20 and +20 for *
* example). Minor fix to majority code to recognize the advantage *
* of having a majority when the opponent has no passers or majority *
* even if the candidate in the majority is not an 'outside' passer *
* candidate. Minor change to passed pawns so that a protected *
* passed pawn is not considered a winning advantage if the *
* opponent has two or more passed pawns. But in input_status *
* would cause an infinite loop if you reset a game to a position *
* that was in book, after searching a position that was not in *
* the book. Bug in position learning fixed also. This was caused *
* by the new hashing scheme Tim Mann introduced to avoid locking *
* the hash table. I completed the changes he suggested, but forgot *
* about how it might affect the position learning since it is also *
* hash-based. Needless to say, I broke it quite nicely, thank you. *
* *
* 17.8 This is the version used in the first ICC computer chess *
* tournament. Crafty won with a score of 7.0/8.0 which included *
* only 2 draws and no losses. Changes are minimal except for a few *
* non-engine syntax changes to eliminate warnings and fix a bad bug *
* in 'bench.c' that would crash if there was no books.bin file. *
* *
* 17.9 LearnPosition() called with wrong arguments from main() which *
* effectively disabled position learning. This was broken in 17.7 *
* but is now fixed. *
* *
* 17.10 Minor change to "threat" extension now only extends if the null- *
* move search returns "mated in 1" and not "mated in N". This *
* tends to shrink the trees a bit with no noticable effect in *
* tactical strength. EvaluatePawns() was not doing a reasonable *
* job of recognizing blocked pawns and candidate passers. It did *
* not do well in recognizing that the pawn supporting a candidate *
* could not advance far enough to help make a real passed pawn. *
* Minor change to RepetitionCheck() to not count two-fold repeats *
* as draws in the first two plies, which prevents some odd-looking *
* repeats at the expense of a little inefficiency. Ugly repetition *
* bug fixed. Rephead was off by one for whatever side Crafty was *
* playing which would screw up repetition detection in some cases. *
* Minor bug in main() that would report stalemate on some mates *
* when the ponder score was forgotten. *
* *
* 17.11 Fail high/low logic changed to move the ++ output into Iterate() *
* where the -- output was already located. (This was done for *
* consistecy only, it was not a problem. New function to detect *
* draws RepetitionCheckBook() was added to count two-fold repeats *
* as draws while in book. This lets Crafty search to see if it *
* wants tht draw or not, rather than just repeating blindly. Minor *
* bug in "go"/"move" command fixed. The command did not work if *
* the engine was pondering. Minor change to Evaluate() that makes *
* BAD_TRADE code more acurate. Minor change to pawn majority code *
* to fix two bugs. White pawns on g2/h2 with black pawn on h7 was *
* not seen as a majority (outside candidate passer) but moving the *
* black pawn to g7 made it work fine. Also if both sides had an *
* equal number of pawns (black pawn at a7/b7, white pawns at b2/c2 *
* the code would not notice black had an outside passer candidate *
* since pawns were 'equal' in number. *
* *
* 17.12 BookUp() will now create a book with all sorts of games in it, so *
* long as the various games have the FEN string to properly set the *
* initial chess board position. *
* *
* 17.13 Endgame evaluation problem fixed. King scoring now dynamically *
* chooses the right piece/square table depending on which side of *
* the board has pawns, rather than using root pre-processing which *
* could make some gross errors. Glitch with majorities would make *
* an "inside majority candidate" offset a real outside passed pawn *
* even if the candidate would not be outside. A suggestion by *
* Blass Uri (CCC) was added. This adds .01 to tablebase scores if *
* the side on move is ahead in material, and -.01 if the side on *
* move is behind in material (only for drawn positions.) the *
* intent is to favor positions where you are ahead in material *
* rather than even in material, which gives 'swindle mode' a chance *
* to work. Bug in EvaluateDraws() would mis-categorize some B+RP *
* (wrong bishop) as drawn, even if the losing king could not make *
* it to the corner square in time. *
* *
* 17.14 Another endgame evaluation problem fixed. The outside passed *
* pawn code worked well, up until the point the pawn had to be *
* given up to decoy the other side's king away from the remainder *
* of the pawns. Crafty now understands the king being closer to *
* the pawns than the enemy king, and therefore transitions from *
* outside passer to won king-pawn ending much cleaner. New command *
* "selective" as requested by S. Lim, which allows the user to *
* set the min/max null move R values (default=2/3). They can be *
* set to 0 which disables null-move totally, or they can be set *
* larger than the default for testing. Minor changes to init.c *
* sent by Eugene Nalimov to handle 64 bit pointer declarations for *
* win64 executable compilation. NetBSD changes included along with *
* a new Makefile that requires no editing to use for any known *
* configuration ("make help" will explain how to use it). This was *
* submitted by Johnny Lam. Serious changes to the outside passed *
* pawn code. The evaluator now understands that outside passers *
* on _both_ sides of the board is basically winning. Same goes for *
* candidate passers. *
* *
* 18.0 Bug in EvaluateDraws() could incorrectly decide that if one side *
* had only rook pawns in a king/pawn ending, the ending was a draw. *
* Even if the other side had pawns all over the board. Passed pawn *
* scores increased a bit. Minor change to "bad trade" code to turn *
* off in endings. S list removed. The trojan horse check is now *
* automatically enabled when the key position is recognized at the *
* root of the tree. It is disabled once the key position is no *
* longer seen at the root. Bug in BookUp() would break if a FEN *
* string was included in a game used for input. SetBoard() was *
* setting castling status incorrectly. Internal iterative *
* deepening bug could (on very rare occasions) cause Crafty to try *
* to search an illegal move that would bomb the search. This *
* version fully supports the new xboard protocol version 2. One *
* other major change is that the eval is now consistently displayed *
* as +=good for white, -=good for black. In the log file. In the *
* console output window. And when whispering/kibitzing on a chess *
* server. This should eliminate _all_ confusion about the values *
* that are displayed as there are now no exceptions to the above *
* policy of any kind. Book() was changed so that if it notices *
* that the opponent has a "stonewall pattern" set up (IE Crafty *
* is black, has a pawn at e7 or e6, and the opponent has pawns at *
* d4/f4) then it won't play a castle move from book. It will do a *
* normal search instead and let the evaluation guide it on whether *
* to castle or not (generally it won't unless it is forced). *
* *
* 18.1 Easy move code broken, so that no move ever appeared to be "easy" *
* even if it was the only possible recapture move to make. A minor *
* problem in analysis mode dealing with pawn promotions was fixed. *
* It was possible for a move like h8=Q to be rejected even though *
* it was perfectly legal. *
* *
* 18.2 Minor bug in analyze mode would break the "h" command when black *
* was on move, and show one less move for either side that had *
* actually been played in the game. Another bug also reversed the *
* sign of a score whispered in analysis mode. Recapture extension *
* is disabled by default. To turn it on, it is necessary to use *
* -DRECAPTURE when compiling search.c and option.c. LearnBook() *
* has been modified to 'speed up' learning. See the comments in *
* that module to see how it was changed. LearnResult() has been *
* removed. LearnBook() is now used to do the same thing, except *
* that a good (or bad) score is used. *
* *
* 18.3 Minor bug in "avoid_null_move" test used R=2 for the test rather *
* than testing R=2/3 as the real null-move search uses. The kibitz *
* for "Hello from Crafty Vx.xx" has been moved so that it works *
* with the new xboard/winboard 4.2.2 versions. Book learning was *
* badly broken in the previous version and has been fixed/tested. *
* *
* 18.4 Recapture extension was left in SearchParallel() by mistake. This*
* has now been protected by a #ifdef just like it was in Search(). *
* Bug in RepetitionCheck() was causing problems in SMP versions. *
* The entire repetition list code was modified to clean this up. *
* The problem was most noticable on things like fine #70. Bug in *
* LearnImportBook() confused the learn value sign, due to the other *
* changes to make +=white all the time. opposite bishop scoring *
* has been beefed up a bit to avoid these drawish endings. *
* *
* 18.5 Minor change to RootMove() to use Quiesce() rather than the more *
* complicated way it was ordering with Evaluate()/EnPrise(). This *
* is no faster, but it is simpler and eliminated the need for the *
* EnPrise() function totally, making the code a bit smaller. Bug *
* in EvaluateDraws() would let it think that the bishop+wrong rook *
* pawn endings were winnable if both kings were very close to the *
* queening square, even with the wrong bishop. *
* *
* 18.6 "New" no longer produces a new log.nnn/game.nnn file if no moves *
* have actually been played. Minor change to rook scoring gives a *
* penalty when a rook has no horizontal (rank) mobility, to avoid *
* moves like Ra2 protecting the pawn on b2, etc. Glitch in the *
* code that initializes is_outside[][] and is_outside_c[][] could *
* cause missed outside pawn cases to happen. This has been there *
* a long time. *
* *
* 18.7 BOOK_CLUSTER_SIZE increased to 2000 to handle making really large *
* books. A book made without this change could produce clusters *
* that would cause memory overwrites. *
* *
* 18.8 Recapture extension turned back on for a while. Changes to the *
* evaluation code, particularly EvaluatePawns() to make it more *
* efficient and accurate. IE it was possible for an isolated pawn *
* to be penalized for being isolated, weak, and blocked, which made *
* little sense. *
* *
* 18.9 Book() modified to increase the responsiveness of book learning. *
* The new code, plus the default weights for the book parameters *
* now make Crafty learn very aggressively and repeat good opening *
* lines and avoid bad ones. *
* *
* 18.10 Minor bug in book.c would let Crafty play lines that were very *
* rarely played even though there were others that had been played *
* far more times and were more reliable. King safety scores ramped *
* up a bit and made more "responsive". *
* *
* 18.11 Minor bug in EvaluateDevelopment() found by Bruce Moreland. The *
* pawn ram code is now disabled when playing a computer, although *
* the normal 'blocked pawn' code is always active. Bug in the code *
* that penalizes a rook with no horizontal mobility was fixed. If *
* the first rook scored had horizontal mobility, the second rook *
* appeared to have this mobility as well, which was wrong. Pawn *
* hash statistics were wrong on longer searches due to an int *
* overflow on a multiply and divide calculation. This has been *
* re-ordered to avoid the overflow. For unknown reasons, epd *
* support was disabled. It is now enabled as it should be. Some *
* strange adjustements to root_alpha/root_beta were removed from *
* searchr.c. They were probably left-over from some sort of test. *
* *
* 18.12 Bug in EvaluateDraws() fixed to not call KBB vs KN a draw if the *
* correct tablebase is not available. Bishop pair scores now vary *
* depending on how many pawns are left on the board. A pair is not *
* worth a lot if there are 7-8 pawns left as most diagonals will be *
* blocked by pawns. Test() modified so that it will now run using *
* an EPD test suite with am/bm and id tags. The old testfile for- *
* mat will continue to work for a while, but Test() now notices the *
* EPD format and processes it correctly. A new way of handling the *
* search extensions is in place. With the old approach, one ply *
* could not extend more than one full ply. With the new approach, *
* borrowed from Deep Blue, two consecutive plies can not extend *
* more than two plies total. It averages out to be the same, of *
* course, but the effect is a bit different. Now it is possible *
* for a check and recapture to be applied at the same ply, where *
* they could not before (since a check was already a full one-ply *
* extension). Whether this is better or not is not clear yet, but *
* it is worth careful analysis. EvaluateDraws() has been replaced *
* by EvaluateWinner(). This function returns an indicator that *
* specifices whether white, black, both or neither can win in the *
* present position. *
* *
* 18.13 Deep Blue extension limit removed and restored to one ply of *
* extension per ply of search. Pruning in q-search fixed so that *
* a capture will be considered if it takes the total material on *
* the board down to a bishop or less for the opponent, as that can *
* greatly influence the evaluation with the EvaluateWinner() code. *
* As the 50 move rule draws near, the hash table scores are marked *
* as invalid every 5 moves so that hashing can't hide potential *
* 50-move-rule draws. Lazy evaluation code modified to be more *
* conservative, since in endgames the positional score can be a *
* large change. EvaluatePassedPawnRaces() fixed so that if one *
* side has two pawns that are far enough apart, it will recognize *
* that even though the king is "in the square" of either, it can't *
* always stay in the square of one if it has to capture the other. *
* Pawn hash signature restored to 64 bits after testing proved that *
* 32 was producing an unacceptable number of collisions. Search *
* node counter is now 64 bits as well to avoid overflows. Bug in *
* the outside passed pawn code fixed (bad mask). *
* *
* 18.14 Minor bug in ResignOrDraw() code caused Crafty to not offer draws *
* although it would accept them when appropriate. Rook vs Minor *
* is now evaluated as "neither side can win" an oversight in the *
* EvaluateWinner() code. Minor bug in ResignOrDraw() would fail to *
* offer draws due to the +0.01/-0.01 draw scores returned by the *
* EGTB probe code. *
* *
* 18.15 Change in endgame draw recognition to handle the case where one *
* side appears to be in a lost ending but is stalemated. The code *
* now evaluates such positions as "DrawScore()" instead. The code *
* to accept/decline draws has been modified. When a draw offer is *
* received, a global variable "draw_offer_pending" is set to 1. *
* When the search for a move for Crafty terminates, Crafty then *
* uses this value to decide whether to accept or decline the draw. *
* This means that the accept/decline won't happen until _after_ the *
* search has a chance to see if something good is happening that *
* should cause the draw to be declined, closing a timing hole that *
* used to exist that let a few "suspects" get away with draws that *
* should not have happened (ie Crafty has - scores for a long time, *
* the opponent suddenly fails low and sees he is losing and offers *
* a draw quickly. Crafty would accept before doing a search and *
* noticing that it was suddenly winning.) minor evaluation change *
* to notice that K+B+right RP vs K+B is not necessarily won if the *
* weaker side has a bishop of the right color. *
* *
* 19.0 Significant change to the search extension limits. First, the *
* limit of no more than 1 ply of extensions per ply has been tossed *
* out. Now, any number of extensions are allowed in the first N *
* plies, where N=iteration_depth of the current iteration. After *
* the first N plies, extensions are reduced by 50% for the next N *
* plies. They are then reduced by another 50% for the next N plies *
* and then completely disabled after that. IE for a 12 ply search, *
* all extensions (even > one ply) are allowed for the first 12 *
* plies, then the extensions are reduced by 1/2 for the next 12 *
* plies, then by 1/4 for the next 12 plies, then turned off from *
* that point forward. Minor tweak (suggested by GCP) to reduce the *
* time limit by 1/4 for ponder=off games was done in time.c. Fix *
* to EvaluateWinner() to correctly realize that KR[BN] vs KRR is a *
* draw for the KRR side if it doesn't have at least a pawn left. *
* Minor bug in RejectBookMove() would reject all moves if the op- *
* ponent had a stonewall-type pawn set-up. It was supposed to only *
* reject castling into the attack. Minor change to code in the *
* EvaluateMaterial() function to lower the penalty for sacrificing *
* the exchange. it was considered just as bad as trading a rook *
* for two pawns which was wrong. Change to hashing code so that we *
* can now determine that a hash entry came from the EGTB so that *
* PVs are displayed with <EGTB> when appropriate, not <EGTB> if it *
* originally came from the EGTB but later <HT> when it was picked *
* up from the hash table instead. Minor changes to search/searchmp *
* to make them identical in "look" where possible, for consistency *
* in source reading if nothing else. If the first argument on the *
* command-line is "xboard" or if the environment variable *
* "CRAFTY_XBOARD" is set, Crafty sends a "feature done=0" command *
* to tell xboard it has not yet initialized things. Significant *
* changes to EvaluateWinner() to recognize new cases of draws such *
* as Q+minor+nopawns vs Q+pawns as unwinnable by the Q+minor side. *
* Other cases were fixed/improved as well. *
* *
* 19.1 Changes to the outside passed pawn and outside candidate pawn *
* code to more correctly recognize when one side has a simple end- *
* game position that is easy to win. Futility pruning and razoring *
* (Jeremiah Penery) was added. To endable it, you will need to add *
* -DFUTILITY to the Makefile options, otherwise it is disabled by *
* default. EvaluateWinner() had a bug dealing with KR vs KN or *
* KRR vs KRN(B) that has been fixed. *
* *
* 19.2 CCT-5 version 01/20/03. *
* Changes to the LimitExtensions() macro. The extensions are now *
* a bit more aggressive, but after 2*iteration_depth, then they *
* taper off smoothly so that by the time the depth reaches *
* 4*iteration_depth, the extensions are cut to zero. Fixed bug in *
* EvaluatePawns() that missed candidate passed pawns so that the *
* new endgame stuff didn't work completely. Change to hash.c to *
* combine the two hash tables into one so that the two probed *
* entries are adjacent in memory to be more cache friendly. A bug *
* in moving a replaced entry from depth-preferred to always-store *
* caused the moved entry to go to the wrong address which would *
* make it impossible to match later. New hash table layout is more *
* cache-friendly by putting one entry from depth-preferred table *
* with two entries from always-store, so that they often end up in *
* the same cache-line. *
* *
* 19.3 Change to EvaluateMaterial to realize that a rook for five pawns *
* is also likely a "bad trade." Adaptive hash table size code was *
* added so that the hash size is set automatically based on the *
* estimated NPS and time per move values for a specific "level" *
* command setting. RepetitionCheck() rewritten. The old code had *
* an unexplained bug that would overlook repetitions in a parallel *
* search in rare cases. The old cold was complex enough that it *
* was time to rewrite it and simplify it significantly. *
* *
* 19.4 Initial depth "seed" value changed to iteration_depth + 1/2 ply, *
* so that fractional extensions kick in earlier rather than deeper *
* in the search. This performs _much_ better in tactical tests *
* such as WAC and similar suites. Minor book fix for a bug that *
* could cause a crash with book=off in xboard/winboard. *
* *
* 19.5 Default draw score set to 1, because endgame table draws can be *
* 0, -.01 or +.01, which translates to -1, 0 or 1 in real scores *
* inside Crafty. +1 means a draw where white has extra material *
* and that would break accepting draws with such a score. A few *
* NUMA-related changes. One global variable was made thread- *
* private to avoid cache thrashing. Split blocks are now allocated *
* by each individual processor to make them local to the specific *
* processor so that access is much faster. CopyToSMP() now tries *
* to allocate a block for a thread based on the thread's ID so that *
* the split block will be in that thread's local memory. A few *
* other NUMA-related changes to help scaling on NUMA machines. *
* *
* 19.6 New egtb.cpp module that cuts decompression indices memory by 50% *
* with no harmful side-effects. Fixes to NUMA code to make SMP and *
* non-SMP windows compiles go cleanly. *
* *
* 19.7 Changes to draw code so that Crafty will first claim a draw and *
* then play the move, to avoid any confusion in whether the draw *
* was made according to FIDE rules or not. Minor bug in evaluate() *
* dealing with candidate passed pawns fixed. A few additions to *
* support my AMD Opteron inline assembly for MSB(), LSB() *
* and PopCnt() procedures. *
* *
* 19.8 Changes to lock.h to (a) eliminate NT/alpha, since Microsoft no *
* longer supports the alpha, which makes lock.h much more readable. *
* CLONE is no longer an option either, further simplyfying the .h *
* files. New mode option "match" which sets an aggressive learning *
* mode, which is now the default. The old learning mode can be set *
* by using the command "mode normal". Memory leak in new windows *
* NUMA code fixed by Eugene Nalimov. AMD fix to make the history *
* counts thread-local rather than global (to avoid excessive cache *
* invalidate traffic). *
* *
* 19.9 Two new pieces of code submitted by Alexander Wagner. The first *
* adds speech to Crafty for unix users. /opt/chess/sounds needs to *
* exist and the common/sounds.tar.gz file needs to be untarred in *
* directory. "Speech on*off" controls it. A new annotatet command *
* outputs the annotated file in LaTeX format for those that prefer *
* that platform. Lots of source reformatting to make indenting and *
* other things more consistent, using the unix "indent" utility. *
* Singular extension (simplistic approach) has been added and needs *
* -DSINGULAR to activate it. Once it has been compiled in, you can *
* turn it on/off by setting the singular extension depth using the *
* ext command. Default is on if you compile it in. Ext/sing=0 *
* disable it. Changes to non-COMPACT_ATTACKS code to shrink the *
* array sizes. This was done primarily for the Opteron where the *
* COMPACT_ATTACKS stuff was a bit slower than the direct look-up *
* approach. This change reduced the table sizes by 75%. A small *
* change to Evaluate() to better handle the 50-move draw problem. *
* What used to happen was when the counter hit 100 (100 plies since *
* last capture or pawn push) the score just dumped to DrawScore() *
* instantly. It was possible that by the time the draw was seen, *
* it was too late to do anything to avoid it without wrecking the *
* position. what happens now is that once the 50-move counter *
* reaches 80 plies (40 moves by both sides with no pawn push or *
* capture) the score starts dropping toward DrawScore() no matter *
* which side is winning. Dave Slate called this a "weariness *
* factor" in that after playing 40 moves with no progress, the *
* evaluation shows that the program is getting "weary". The idea *
* is that the score starts to slip over the last 10 moves by each *
* side to that if either can do something to reset the counter, *
* they will do it sooner rather than later. *
* *
* 19.10 A fix to the EvaluateWinner() code to recognize that while KRB vs *
* KR can not normally be won by the KRB side, we require that the *
* KR side not be trapped on the edge of the board, where it can be *
* mated. FUTILITY code put back in. 19.9 will be the SE version *
* for those wanting to play with it. New "learn" command option to *
* allow the user to set the position learning parameters that are *
* used to trigger position learning and disable position learning *
* after the game is already lost. The command syntax is as follows *
* "learn trigger cutoff" and are expressed as fractions of a pawn *
* with a decimel point. The default is learn .33 -2.0 which says *
* to do position learning when the score drops 1/3 of a pawn, but *
* turn it off after the score reaches -2.00 as the game is already *
* lost and learning won't help at this point. This is the CCT-6 *
* version exactly as played in the CCT-6 tournament. *
* *
* 19.11 A fix to the Annotate() code that could, in certain cases, fail *
* to display N moves when asked. This happened when there were *
* fewer than N moves total, and on occasion it would not display *
* all the moves that were possible, omitting the last one. Fix to *
* egtb.cpp to correctly set 16 bit index mode for a few of the *
* recent 6-piece tables. *
* *
* 19.12 Fix to allocating split blocks that did not let all blocks get *
* used, which would produce slow-downs on large parallel boxes *
* (cpus > 8-16). Change to fail-high/fail-low window adjustment. *
* I now use the old Cray Blitz approach ("Using time wisely - *
* revisited", JICCA) where a fail-high (or low) now adjusts the *
* root alpha or beta bound by 1 pawn on the first fail, another two *
* pawns on the second failure, and finally relaxes the bound to *
* +/- infinity on the third fail for the same move. This speeds up *
* searching many fail-high/fail-low conditions, although it will *
* occasionally cause the search to take a bit longer. *
* *
* 19.13 Fix to evaluating split passed pawns. Code is cleaner and is not *
* applied if the opposing side has any pieces at all since a piece *
* and the king can stop both. New egtb.cpp that opens the tables *
* approximately 20-25% faster is included in this version (code by *
* Eugene Nalimov of course). *
* *
* 19.14 New "eval" command (eval list and eval help to start) allow a *
* user to modify all internal evaluation values via commands that *
* may be entered directly or via the .craftyrc/crafty.rc init file. *
* This was mainly done for the automated evaluation tuning project *
* I am working on with Anthony Cozzie, but it will be useful for *
* merging Mike Byrne's "personality" stuff as well. New command *
* "personality load/save <filename>" which saves eval and search *
* parameters to create new personalities that can be loaded at any *
* time. "Crafty.cpf" is the "default" personality file that is *
* used at start-up if it exists. Evaluation tuning changes based *
* on some results from the new annealing code, although all of the *
* annealed values are not yet fully understood nor utilized yet. *
* LearnBook() is now used to learn good and bad game results. IE *
* if Crafty wins with a particular opening, it will remember it as *
* good and try it again, in addition to the previous method that *
* would remember bad openings and avoid them. It also now handles *
* draws as well which can make slightly bad openings appear better. *
* Minor change to SMP code to eliminate the possibility of a shared *
* variable getting overwritten unintentionally. Several changes to *
* evaluation weights and evaluation code as testing for the WCCC *
* continues. New "help" command uses a file "crafty.hlp" which now *
* contains all the help information. This makes the help info *
* easier to maintain and gets rid of a bunch of printf()s in the *
* Option() source (option.c). Rewrite of the "list" code. Crafty *
* now supports six lists, AK (auto-kibitz), B (blocker), C (comp), *
* GM, IM and SP (special player). The SP list has two extra items *
* that can be specified to go with a player's name, namely a book *
* filename (to replace the normal books.bin, but not book.bin) and *
* a personality file that will be loaded each time this particular *
* named opponent plays. The format is available in the new help *
* facility. Bug fix for outside passed pawn code that would cause *
* an outside passer to appear to be a winning advantage even if the *
* opponent has a protected passer, which easily negates the outside *
* passer's threat. *
* *
* 19.15 Fix to outside passed pawn code that requires pawns on both sides *
* of the board for the side with an "outside passer" or "outside *
* candidate" to avoid some bizarre evaluations. Sel 0/0 now works *
* without crashing Crafty. This would fail in previous versions as *
* the hash signature would be modified but not restored. Slightly *
* more conservative limit on using null-move search to head off a *
* few notable zugzwang problems was added. Fix to time control *
* code to remove a hole that could cause a divide-by-zero at a time *
* control boundary. Stonewall detection removed completely as it *
* appears to be no longer needed. Rook scoring changed to better *
* evaluate "open files" by measuring mobility on them. Complete *
* removal of Phase() (phase.c) and references to the opening, *
* middlegame and endgame phases as they were no longer referenced *
* anywhere in the code. *
* *
* 19.16 Fix to "Trojan code" to eliminate the time limit exclusion since *
* many users still have old and slow hardware, and the time limit *
* was not set correctly when PreEvaluate() was called anyway. The *
* code to display fail-high/fail-low information was cleaned up so *
* that the +1 or +3 now makes sense from the black side where the *
* score is really going down (good for black) rather than showing *
* a +3 fail high (when Crafty is black) and the score is really *
* going to drop (get better for black). Now the fail-high-fail-low *
* +/- sign is also relative to +=good for white like the scores *
* have been for years. Adjustments to pawn evaluation terms to *
* improve the scoring balance. "New" now terminates parallel *
* threads (they will be re-started when needed) so that we don't *
* burn CPU time when not actually playing a game. *
* *
* 19.17 Changes to pawn evaluation to limit positional scores that could *
* get a bit out of sane boundaries in some positions. *
* *
* 19.18 HashProbe() no longer adjusts alpha/beta bounds if the entry is *
* not good enough to terminate the search here. This has helped *
* speed things up (reduced size of tree) over many test positions *
* so either it was buggy or not worthwhile. Regardless, it is now *
* 'gone'. Connected passed pawns now scored as a simple pair of *
* pawns that are better as they are advanced, the old connected *
* passed pawns on the 6th rank special code has been removed. *
* *
* 19.19 RepetitionDraw() had a bug that would cause it to miss a draw *
* claim on the 50th move, often making a strange (losing) move that *
* would not lose if the draw is was claimed, but which would cause *
* a loss if the draw was not claimed because the piece might be *
* instantly captured if the opponent can play a move. *
* *
* 19.20 Bug in the EvaluateMaterial() (bad trade) code that would not *
* penalize a single piece vs 3 pawns properly. Now the penalty is *
* added in unless the side with the piece has nothing else to go *
* with it at all (no pawns or other pieces). Pawn scoring changed, *
* doubled pawns were scored too badly because the penalties were *
* added twice (as expected) but they were set as if they were just *
* added once. Eval command also had a bug in displaying the pawn *
* evaluation parameters. Move input changed to accept pawn *
* promotions of the form a8Q (this is needed as ChessBase violates *
* the PGN/SAN standard that mandates a8=Q as the proper syntax for *
* pawn promotions.) annoying glitch in epdglue.c that would *
* produce the wrong score for positions with exactly one legal move *
* was fixed. New InvalidPosition() function verifies that FEN *
* setup positions are reasonable, without extra pawns or too many *
* pieces total, etc. Passed pawn to 7th search extension removed, *
* mate threat extension tuned down to 1/2 ply. Bug in SetBoard() *
* fixed. This bug made it impossible to import many epd records *
* due to incorrectly handling the wtm flag. This was introduced in *
* the recent changes to disallow certain types of illegal positions *
* that were impossible (more than 9 queens of one color, etc.) new *
* eval term for space added. This simply counts the number of *
* squares on each rank attacked by pawns, and then multiplies by a *
* constant that scales the attacks so that attacking ranks on the *
* opponent's side of the board is more valuable than attacking *
* squares on our side of the board and vice-versa. Significant *
* coding changes for the unix parallel search. POSIX threads are *
* gone, due to too many differences between vendor's implementation *
* details. Crafty now uses SYSV shared memory to share the search *
* data (this is exactly the same parallel search approach always *
* used, but with a completely different implementation) and fork() *
* to spawn processes for each CPU. It simply became too much work *
* to figure out what each vendor was doing about CPU time, how *
* threads were scheduled, plus debug thread library implementations *
* that were often buggy. There are no performance benefits to this *
* approach other than falling back to features found in all Unix *
* implementations. New NUMA changes to make sure that the local *
* thread "blocks" are actually allocated on the NUMA node where *
* the process actually runs, rather than on a remote node that *
* will cause extra memory latency for often-used memory data. Bug *
* in EvaluatePawns() caused the outside passer / outside *
* candidate bonus to be triggered when the opponent has a simple *
* protected passed pawn. Since the decoy value is nil with a *
* protected passer (we can't take the supporing pawn or the passer *
* will run) the outside candidate or passer doesn't help. Bug in *
* king safety caused pieces to be attracted to the opponent's king, *
* even in simple endgames, inflating/deflating the score for a *
* feature that was pointless. (2005 WCCC final version). *
* *
* 20.0 First in a new series. First change is to produce an endian- *
* independent opening book. The format has not changed so that old *
* book.bin/books.bin files will work fine, but they may now be *
* freely between big-endian and little-endian architectures. This *
* makes the binary format compatible between a PC and a Sun or HP *
* box, for example, so that just one book.bin file is needed. *
* *
* 20.1 First step toward a complete redesign of the evaluation code in *
* Evaluate() (evaluate.c). This first set of changes are mainly *
* restructuring related, an attempt to collect the various bits of *
* evaluation code that are related to a common theme (i.e. All *
* bishop scoring, all passed pawn scoring, etc) are not contained *
* in one routine, with a sensible name. This makes it much easier *
* to find evaluation code and modify it, without having bits and *
* pieces scattered all over the place. Perhaps the most signifi- *
* cant is that the current evaluation has dropped the asymmetric *
* king safety, and later the asymmetric blocked pawn code will go *
* as well. To do this, I did have to make some changes in terms *
* of the "tropism" code. The basic idea is that white's "tropism" *
* bonus in incremented for each white piece that attacks the black *
* king, but it is also decrement for each black piece that attacks *
* the black king, so that a defender offsets an attacker. This has *
* certainly changed the "personality" of how it plays. It is now *
* far more aggressive, and further changes planned for the future *
* will hopefully improve on this change. It is playing quite a bit *
* better, but whether this aggressiveness is "over the top" remains *
* to be seen. Fix to "won kp ending" logic. If one king is closer *
* to the opponent's "average pawn square" than the other, by at *
* least 2 moves, then that side is credited as having a won k+p *
* ending. New code for time allocation testing added. A new *
* "timebook <factor> <moves>" command that says use "factor" extra *
* time (factor is expressed as a percent, 100 means use 100% extra *
* time) tapered off for "moves" out of book. For example, *
* "timebook 100 10" says use 100% extra time on first non-book move *
* followed by 90% extra on the next move, 80% on the next, until *
* after 10 moves we are back to the normal time average. *
* *
* 20.2 Significant evaluation changes to try to limit positional scores *
* so that new tuning can be accomplished. In particular, the king *
* safety code has been greatly simplified, now having two separate *
* components, one for pawn structure, one for piece tropism. A new *
* SearchControl() procedure now handles all the search extensions *
* in one centralized place, shared by normal and parallel search *
* code. The plan is that eventually this piece of code will also *
* be able to recommend search reductions as well as extensions to *
* speed the tree traversal process significantly with a form of *
* of forward pruning that is commonly called "search reductions". *
* *
* 20.3 Search reduction code added. Part of this dates back to 1997 *
* when Bruce Moreland and I played with the idea of reducing the *
* depth on the last part of the move list when it seemed to become *
* fairly certain that no fail-high was going to happen. That was a *
* big search speed improvement, but also risky. Recently, several *
* started to do this again, except they added one fairly useful *
* constraint, that the "history value" for a specific move has to *
* be below some threshold before a reduction can happen. The idea *
* is that we don't want to reduce the depth of moves that have *
* failed high in the past, because they might fail high again if *
* they are not reduced too much. Tord Romstad suggested an *
* additional improvement, namely that if a reduced move does fail *
* high, re-search with the proper (non-reduced) depth to verify *
* that it will fail high there as well. All of this is included *
* in version 20.3, but the values (reduction amount, history *
* threshold, min depth to do a reduction) need serious testing and *
* tuning. The current values are simply "legal" but hardly could *
* be considered optimal without substantial testing. New code to *
* "age" history counters added. After each iteration, this code *
* divides each counter by 2, to scale the values back, so that *
* moves that are no longer causing fail highs will have a history *
* value that won't prevent reduction pruning. The "minimum depth" *
* value indicates how much search to leave after doing a reduction *
* in the tree. A value of 1 ply guarantees that after a reduction *
* is done, there will always be one full-width ply of search done *
* after such reductions to avoid gross tactical oversights. Tuning *
* to extensions to reduce the tree size. The recapture extension *
* has been completely removed, while the check extension has been *
* left at 1.0 as in the past. The mate threat and one-legal-reply *
* extensions are now both set to .75 after extensive testing. This *
* is the CCT8 version of Crafty. *
* *
* 20.4 History counters changed. There is now one large history[8192] *
* array to simplify indexing. More importantly, these values are *
* now limited to a max value of 32000. During the update process, *
* if any value reaches that limit, all values are divided by 2 to *
* prevent deep searches from producing very large history values *
* which would essentially disable late move reductions based on the *
* big history values. The reduce/history=n command now uses values *
* 0 <= n <= 100. A value of 100 will cause all non-tactical moves *
* to be reduced (most aggressive) while a value of 0 will result in *
* no moves being reduced (most conservative). The value, loosely *
* interpreted, means "reduce if a move fails high < n% of the time *
* when at least one move fails high in a search." the default is *
* currently 50%, but further testing is needed. *
* *
* 20.5 Old "mask" code removed and replaced by constants, since this is *
* never intended to run on a Cray specifically any longer. Change *
* to "won king and pawn ending" to make it more accurate, this code *
* is used when there are nothing but pawns left, all on one side of *
* board, and one king is closer to a capturable pawn than the other *
* king is. This is intended to help in outside passed pawn games *
* where one side has to eventually give up the outside passer to *
* decoy the opposing king away from the rest of the pawns. New *
* king safety now factors in king pawn shelter and opponent piece *
* tropism into one score, but the score is now an arithmetic *
* value that goes up more quickly as both indices increase, to do a *
* more accurate evaluation of safety and attacking chances. Change *
* to bishop mobility, which now goes in units of 2 rather than 1, *
* to increase the value of mobility somewhat. Also mobility is now *
* 'centered' in that it is computed as (squares - 6) * 2, to keep *
* the bishop value from going way over its normal range with these *
* new and somewhat larger numbers. *
* *
* 20.6 New eval code to look for bishops that are blocked in the forward *
* direction by friendly pawns. That basically turns a bishop into *
* a "tall pawn" since movement in the critical direction is not *
* possible. *
* *
* 20.7 Manually tuned kinf_safety[][] array values. Modified the new *
* bishop code to only consider the "long diagonal" if the bishop *
* is in either 9-square corner on its own side of the board, so *
* that the short diagonal being open won't offset the long *
* diagonal that is blocked. Bishop-pair bonus is now adjusted by *
* how open or closed the center is. If 3 of the four center pawns *
* are gone, the center is open and the bishop pair bonus is set to *
* the max. If the four center pawns are locked (e4/e5/d5/d6 for *
* example) then the bishop pair bonus is eliminated. if the center *
* is somewhere in the middle of those extremes, then the bishop *
* pair bonus is present but reduced. Castling now is a bit more *
* intelligent. If a side has not castled, then moving either rook *
* receives a penalty, where moving the king or the last unmoved *
* rook receives a larger penalty. If the king has not castled, its *
* 'safety' score is based on the most safe position of the possible *
* options. If neither rook has moved, then the score is based on *
* the safest of the three locations, either in the center where it *
* is, or on the safest wing. If uncastled, this safaty is always *
* reduced a bit to encourage castling before it becomes too late to *
* do so. This was done to avoid a problem where the queen rook had *
* been moved, Crafty had not castled, and it pushed the kingside *
* pawns making it unsafe to castle there, leaving the center as the *
* best place, yet had it not pushed the kingside pawns, castling *
* would have been a better alternative. Two new 16 word vectors, *
* safety_vector[]/tropism_vectorp[] are used to set the edge values *
* for the king_safetyp[][] array. Interior values are filled in *
* based on these two vectors, making it much easier to tweak the *
* king safety scores without pulling your hair out. *
* *
* 20.8 When queens come off, the previous version cut the tropism scores *
* and pawn shelter scores by 1/2 each, which had the effect of *
* dropping the overall score by 75% (the score is a geometric *
* computation). The safety/tropism values are now dropped, but by *
* a smaller amount, since bishops + rooks + knights are still a *
* dangerous threat. *
* *
* 20.9 Simple lazy eval (Mike Byrne) added. This simply avoids the more *
* expensive piece evaluations if the pawn scoring and material *
* leave the score well outside the alpha/beta search window. Looks *
* like a 20% speed improvement in general. *
* *
* 20.10 Change to king safety pawn structure. Open files around the king *
* are dangerous, but the h/g (or b/a) files are more dangerous than *
* the f-e-d-c files since they are much harder to defend against *
* with the castled king in the way. Modified the way the king *
* safety matrix is computed so that at the tropism/pawnstructure *
* values are more sane. It currently will get the same value for *
* array indices of 5,0, 4,1, 3,2, 2,3, 1,4, or 0,5, which is better *
* than what it was doing. I plan to tweak this more later to make *
* 3,2 or 2,3 worse than 4,1 or 1,4 and 0,5 or 5,0, as the latter *
* mean "unsafe king but no piece pressure" or "piece pressure but *
* king pawn shelter is safe" whereas the middle values mean both *
* components of an attack are present, unsafe king position and the
* pieces are closing in. *
* *
* 20.11 Minor fix to late move reduction code. Turns out it is possible *
* to reach the block of code if (first_move) { } with status set to *
* REMAINING_MOVES (this means no captures, no killer, no hash move, *
* no history move, etc). That would let me try a reduction, and if *
* it failed high, we would use that score as-is. We now re-search *
* a fail-high here just like we did in the other block of code so *
* that a fail-high on a reduction search is never trusted. *
* *
* 20.12 Further modifications to king safety initialization code to try *
* scale back the values a bit to control score limits. *
* *
* 20.13 Fix to bench.c to remove two file closes that would wreck the *
* program after the bench command was finished. Also the *
* SMP-time-to-ply measurement was removed since it had no meaning. *
* Old FUTILITY code re-inserted along with an extension limit *
* modification by Mike Byrne to avoid limiting the search extension *
* on one-reply extensions only. New lock.h submitted by Andreas *
* Guettinger to support spinlocks on the PPC architecture (Linux). *
* Some -D configuration options were changed so that none are *
* needed to compile the "standard" Crafty. Futility is normally on *
* now, and -DNOFUTILITY is required to compile it out. The new *
* Makefile gives the configuration options, but the only ones that *
* would normally need setting are the SMP and CPUS= options if you *
* have a SMP platform. *
* *
* 20.14 Fix to EvaluateWinningChances() to correctly evaluate KRP vs KR *
* type endings. Previously this was done in the wrong place and *
* the score would favor the side with the pawn significantly, where *
* the score is now zero. Minor bugfix to code that detects that an *
* illegal position has been set up. It caught every possible *
* problem except for positions with a king (or kings) missing. *
* *
* 20.15 Change to how Crafty chooses where to split. Previously, there *
* was a min remaining depth limit to prevent Crafty from trying to *
* split too close to the frontier nodes. Now that is specified as *
* a percentage of the nominal search depth. For example, the *
* default value is 50%, which says that on a 16 ply search, we can *
* split if at least 8 plies of search are left. This provides *
* better split overhead than a simple limit that doesn't take the *
* actual search depth into consideration. History data arranged to *
* be more cache friendly. The three values for a common history *
* index value are now stored in adjacent memory words to take *
* advantage of pre-fetching within a cache line. Additional *
* tuning of the king safety matrix. *
* *
* 20.16 Evaluation of knights, bishops, rooks, queens and kings is now *
* done on a 1000 point scale, then the sum is divided by 10. This *
* allows us to use the same hashing mechanism, but with finer *
* tuning precision. Minor queen eval tweak for 7th rank position. *
* *
* 20.17 New book learning, with a simplified book system. The export *
* files (book.lrn, position.lrn) no longer are created/used, the *
* learn mechanism no longer touches the real chess board which *
* could cause problems in certain xboard/winboard timing *
* situations. One major learning change is that we now only learn *
* things from "Crafty's perspective". That is, if Crafty loses a *
* game as black, it won't think that opening is good when it plays *
* white since it might well not understand how to win using that *
* particular opening. It will only "learn" on the actual moves it *
* plays in a game. Old "history heuristic" removed. Testing *
* showed that the LMR idea produced better results without the *
* history ordering, since now more moves are reduced, but moves *
* with good history values don't get reduced. *
* *
* 21.0 Finally did the bit-renumbering task so that bit 0 = LSB = A1, *
* to eliminate the 63-n translation to the numbering scheme used *
* on the Cray architecture. For all bit operations now, LSB=0, *
* MSB=7, 15, 31 or 63 depending on the data size. A few minor *
* bugs were fixed along the way as these changes were debugged. *
* Minor bug in EvaluateKings() where it tested for a "won ending" *
* and used a test that was too aggressive. This test did not get *
* things quite right when the two kings were very close together *
* and "opposition" prevented one king from moving closer to the *
* pawns. *
* *
* 21.1 New piece scoring from Tracy, which changes the way pieces are *
* scored based on squares they attack. *
* *
* 21.2 The scores are now scaled better for the transition from middle- *
* game to end-game. Passed pawn scores climb as material is *
* removed from the board, to prevent them from overwhelming the *
* middlegame king safety scores. We do exactly the same scaling on *
* king-safety scores, but they are scaled downward as material is *
* removed so that they "phase out" as the endgame is reached. *
* Weak pawn code changed to more accurately identify weak pawns. *
* These are totaled and then used to index a scoring array that *
* penalizes the number of weak pawns on each side. Pawn islands *
* are now recognized and each side is penalized according to the *
* number of islands he has, more being worse. *
* *
* 21.3 "Magic" move generation is now used, which eliminates the rotated *
* bitboard approach completely. Not a significant speed change, *
* but it is far simpler overall. *
* *
* 21.4 Misc eval changes. More king safety changes to include a tropism *
* distance of 1 for bishops or rooks that can slide to intercept *
* any square surrounding the enemy king. Reduced rook slide score *
* by 40%.
* *
* 21.5 passed pawn extension revisited. Bad trade was giving a penalty *
* for being down an exchange (or a bonus for being up an exchange) *
* which was not expected behavior. This has been fixed. EGTB *
* initialization was being done during the first pass over the *
* RC file, which was too early as the rest of the engine had not *
* been initialized. Now the "egtb" command is the only thing that *
* triggers initialization, and is only processed during the second *
* pass over the RC file after paths have been properly set up. *
* Abs() function bug fix. *
* *
* 21.6 Passed pawn evaluation changed with respect to distant passed *
* pawns and distant majorities. Now, if both have a pawn majority *
* we check to see if one is "distant" (away from the enemy king) as *
* this represents a significant time advantage because the other *
* side has to waste moves to reach and capture the pawn to prevent *
* promotion. LMR no longer uses the history counters, which proved *
* to be essentially random numbers. LMR decisions are now based *
* solely on static characteristics of an individual move, rather *
* than trying to determine how the move affected the search at *
* other points in the tree. New wtm bonus added to evaluation. *
* EvaluateMate() bug fixed where the score was set to a non-zero *
* value which broke EvaluateMate() completely. New mobility code *
* for bishops/rooks encourages better piece placement. Note that *
* there are many other evaluation changes too numerous to list here *
* in detail. *
* *
* 21.7 New reduce at root code added to do reductions at the root, but *
* not on any move that has been a "best move" during the current *
* search, unless the move drops too far in the move list. New nice *
* mode for parallel search terminates threads while waiting on the *
* opponent's move to avoid burning unnecessary CPU time (this nice *
* mode is NOT the default mode however.) -DNOFUTILITY removed as *
* futility is on by default and should not be removed. All of the *
* search() code has been cleaned up and streamlined a bit for more *
* clarity when reading the code. Nasty bug in EvaluatePawns() that *
* unfortunattely used the king squares to make a decision dealing *
* with outside passed pawns, but the hash signature for pawns does *
* not include king position. This code was deemed unnecessary and *
* was summarily removed (not summarily executed, it has had that *
* done far too many times already). *
* *
* 22.0 Redesign of the data structures completed so that Crafty will no *
* longer have duplicated code for wtm and btm cases. This has *
* already resulted in a rewrite of movgen(), swap(), make() and *
* Unmake() and cut that code size by almost exactly 50%. The result *
* has been slightly faster speeds, but also the future benefits *
* will be enormous by eliminating a lot of debugging caused by the *
* duplicated code. Timing change to avoid starting an iteration *
* and wasting significant time. We still search enough to get a *
* quick fail-low, otherwise we stop and make the move and save the *
* time we used to burn. Massive cleanup in the macros used to *
* access much of the data since the new [wtm] approach resulted in *
* many old macros becoming unused. Yet another rewrite of the code *
* that handles repetition detection. There is an undetected bug in *
* the previous code, related to pondering and SMP, that was not *
* obvious. The code was completely rewritten and is now much *
* simpler to understand, and has been verified to be bug-free with *
* massive cluster testing. *
* *
* 22.1 Minor fix for CPUS=1, which would cause compile errors. Other *
* eval tweaks to improve scoring. New "skill" command that can be *
* used to "dumb down" Crafty. "Skill <n>" where n is a number *
* between 1 and 100. 100 is max (default) skill. Skill 70 will *
* drop the playing Elo by about 200 points. Skill 50 will drop it *
* about 400 points. The curve is not linear, and the closer you *
* get to 1, the lower the rating. To use this feature, you need to *
* add -DSKILL to your Makefile options otherwise it is not included *
* in the executable. *
* *
* 22.2 We are now back to using POSIX threads, since all current Linux *
* distributions now use the posix-conforming NTPL implementation *
* which should eliminate the various compatibility issues that *
* caused problems in the past. This also should make the new *
* smpnice mode work correctly for Linux and Windows since they will *
* now both use threads for the SMP search. Fruit-like scoring *
* (interpolation between mg and eg scores) fully implemented. AEL *
* pruning (Heinz 2000) also fully implemented (we had razoring and *
* futility, but not extended futility). "Eval" command has been *
* removed and combined with the "personality" command so that eval *
* parameters can be modified, in addition to some search parameters *
* that also belong in the personality data. Mate threat extension *
* and one legal reply to check extensions have been removed. Tests *
* proved them to be absolutely useless, over 30,000 games for each *
* test showed no gain and sometimes a loss in playing strength with *
* them so we followed the "simple is better" and removed them. The *
* fractional ply code was also removed since the only extension we *
* now use is the "give check" extension which is a whole ply. A *
* significant number of evaluation parameters have been changed, *
* a few even removed as cluster testing helped us find optimal *
* values. There are a few new terms, with more planned. *
* *
* 22.3 Corrected a bug in analysis mode where "back n" would crash. A *
* bad array reference broke this during recent changes. *
* *
* 22.4 Corrected a bug in NextRootMove() that tries to calculate the NPS *
* by adding up the node counters in each used split block. However *
* should you not use all possible threads (mt=n where n is < the *
* max CPUS value compiled in) then all split blocks will not be *
* properly initialized (not even allocated) which will cause a *
* segfault instantly. Pawn island evaluation term has also been *
* removed as cluster testing showed that setting these values to *
* zero produced a +14 Elo gain. There might be a better value for *
* them, but the old value was too high. Further cluster testing is *
* underway to test other (but smaller than original) values to see *
* if one of them turns out to be better than zero. So far, no, but *
* the test has not completed. *
* *
* 22.5 Minor eval tweaks. Pthread_create was called without giving it *
* any attributes for the new thread(s) which makes them default to *
* "joinable". When smpnice=1 terminates threads, the threads hang *
* around using memory expecting that the parent will join with them *
* to check the exit status. We now set "detached" as the proper *
* attribute so that this memory leak no longer happens. *
* *
* 22.6 Compile issue fixed which would cause the pthread_lib calls to *
* be used in a windows compile, which was incorrect. They are now *
* protected by a #if defined(UNIX) && (CPUS > 1) conditional test. *
* *
* 22.7 Windows NUMA support fix to eliminate a memory leak caused by *
* re-malloc'ing the split blocks each time a new game is started. *
* This was not found in the previous memory leak testing as that *
* problem was related to stopping/re-starting threads when using *
* smpnice=1. This is unrelated, but similar, and has been around *
* a long time. *
* *
* 22.8 Modified material imbalance fix from Tracy included. This *
* produced an immediate +7 Elo improvement, and additional tuning *
* is under way. Fix to GenerateChecks(). This code had bugs a few *
* weeks back and they were fixed, but the fixes were somehow lost *
* during copying files among multiple machines. The fixes are now *
* back in and properly saved. *
* *
* 22.9 More eval tuning producing another +10 Elo gain. Curmv[n] was *
* "overloaded" in that it was used to obtain the next move for a *
* parallel thread and was also used to pass back a "fail high" move *
* to store in a "LOWER" hash table entry. This led to some error *
* messages internal to Crafty that could possibly cause problems. *
* There is now a second variable "cutmove" used to pass the move *
* back to eliminate race conditions. Hash.c modified extensively *
* to improve readability as well as to eliminate duplicated code. *
* Internal iterative deepening code removed. No measurable benefit *
* in real game testing led to removal since it is simpler without *
* the code. EvaluateMaterialDynamic() also removed. This was code *
* that implemented ideas suggested by IM Larry Kaufman, but careful *
* testing showed absolutely no effect on game results. Again, we *
* chose "simpler is better" and removed it, as no tuning attempts *
* helped for this code. Nasty pawn hashing bug fix, something that *
* has been around for years. This was essentially the same sort of *
* bug that the "lockless hashing algorithm" addressed for the main *
* hash table, where out-of-order memory writes could produce a hash *
* signature and the 64 bit word with score and best move which did *
* not "go together". The same thing happens in pawn hashing, *
* except that an entry is 32 bytes rather than 16, giving even *
* higher probability of an entry that contains mismatched pieces. *
* In the best case, we just got a bad score. In the worst case, *
* this could cause a program crash since some of the data might be *
* invalid, yet it can be used in ways that produce impossible array *
* subscripts that would cause (very rarely) a segmentation fault. *
* The solution was to do the same lockless hashing algorithm where *
* the key is XORed with the other three 64 bit words when the entry *
* is stored, then XORed with them again when we try to match. If *
* the entry is mismatched, the signature will not match anything *
* and we simply will not use the bad data and do a normal pawn *
* evaluation to compute valid values. *
* *
* 23.0 Essentially a cleaned up 22.9 version. Comments have been *
* reviewed to make sure they are consistent with what is actually *
* done in the program. Major change is that the random numbers *
* used to produce the Zobrist hash signature are now statically *
* initialized which eliminates a source of compatibility issues *
* where a different stream of random numbers is produced if an *
* architecture has some feature that changes the generator, such *
* as a case on an older 30/36 bit word machine. The issue with *
* this change is that the old binary books are not compatible and *
* need to be re-created with the current random numbers. The *
* "lockless hash table" idea is back in. It was removed because *
* the move from the hash table is recognized as illegal when this *
* is appropriate, and no longer causes crashes. However, the above *
* pawn hash issue showed that this happens enough that it is better *
* to avoid any error at all, including the score, for safety. We *
* made a significant change to the parallel search split logic in *
* this version. We now use a different test to limit how near the *
* tips we split. This test measures how large the sub-tree is for *
* the first move at any possible split point, and requires that *
* this be at least some minimum number of nodes before a split can *
* be considered at this node. The older approach, which based this *
* decsion on remaining search depth at a node led to some cases *
* where the parallel search overhead was excessively high, or even *
* excessively low (when we chose to not split frequently enough). *
* This version appears to work well on a variety of platforms, even *
* though NUMA architectures may well need additional tuning of this *
* paramenter (smpsn) as well as (smpgroup) to try to contain most *
* splits on a single NUMA node where memory is local. I attempted *
* to automate this entire process, and tune for all sorts of plat- *
* forms, but nothing worked for the general case, which leaves the *
* current approach. When I converted back to threads from *
* processes, I forgot to restore the alignment for the hash/pawn- *
* hash tables. The normal hash table needs to be on a 16 byte *
* boundary, which normally happens automatically, but pawn hash *
* entries should be on a 32 byte boundary to align them properly in *
* cache to avoid splitting an entry across two cache blocks and *
* hurting performance. New rook/bishop cache introduced to limit *
* overhead caused by mobility calculations. If the ranks/files the *
* rook is on are the same as the last time we evaluated a rook on *
* this specific square, we can reuse the mobility score with no *
* calculation required. The code for "rook behind passed pawns" *
* was moved to EvaluatePassedPawns() so that it is only done when *
* there is a passed pawn on the board, not just when rooks are *
* present. Book learning has been greatly cleaned up and *
* simplified. The old "result learning" (which used the game *
* result to modify the book) and "book learning" (which used the *
* first N search scores to modify the book) were redundant, since *
* result learning would overwrite whatever book learning did. The *
* new approach uses the game result (if available) to update the *
* book database when the program exits or starts a new game. If *
* a result is not available, it will then rely on the previous *
* search results so that it has some idea of whether this was a *
* good opening or not, even if the game was not completed. Minor *
* LMR bug in SearchRoot() could do a PVS fail-high research using *
* the wrong depth (off by -1) because of the LMR reduction that had *
* been set. The normal search module had this correct, but the *
* SearchRoot() module did not. EvaluateDevelopment() was turned *
* off for a side after castling. This caused a problem in that we *
* do things like checking for a knight blocking the C-pawn in queen *
* pawn openings. Unfortunately, the program could either block the *
* pawn and then castle, which removed the blocked pawn penalty, or *
* it could castle first and then block the pawn, making it more *
* difficult to develop the queen-side. We now enable this code *
* always and never disable it. This disable was done years ago *
* when the castling evaluation of Crafty would scan the move list *
* to see if Crafty had castled, when it noticed castling was no *
* longer possible. Once it had castled, we disabled this to avoid *
* the lengthy loop and the overhead it caused. Today the test is *
* quite cheap anyway, and I measured no speed difference with it on *
* or off, to speak of. Now we realize that the knight in front of *
* the C-pawn is bad and needs to either not go there, or else move *
* out of the way. *
* *
* 23.1 Xboard protocol support slightly modified so that draw results *
* are now sent after the move that causes the draw. They were *
* always sent before a move if the position prior to the move was *
* drawn, but they were also sent just before playing a move to work *
* around a xboard protocol race condition where I can send a move, *
* and then a draw claim (xboard 'result string') and the GUI sees *
* my move, relays it to my opponent, and gets an instant reply that *
* it then sees before my draw claim. After making this move and *
* forwarding it to me, it now thinks the draw claim is invalid. *
* slight tweak to queen material value and the way our bishop pair *
* scoring is done. The old razoring code has been removed. It is *
* redundant with LMR, and it had the unwanted side-effect of *
* reducing a few of the moves two plies. The futility pruning has *
* been modified to work at the last N plies. We have an array of *
* pruning margins (tuned on the cluster) where anytime the depth is *
* less than "pruning_depth" we try the futility test. If the test *
* succeeds, that move is discarded and not searched at all. Move *
* ordering code modified slightly to call Swap() fewer times if the *
* goodness of the capture can still be accurately assessed without *
* the call. Hash table has been changed to use a bucket of 4 *
* entries similar to a 4-way set associative cache. When a store *
* is attempted, we replace the least useful entry (see hash.c for *
* details). Additionally the hash table is forced to a 64 byte *
* boundary alignment so that a bucket aligns on the start of a *
* cache line for efficiency. The old approach used 3 entries per *
* bucket, the Belle two-table approach, which caused 1/2 of the *
* cache probes to result in two cache line reads rather than just *
* one. Slight modification to "time overflow" logic. Now, if the *
* score drops on the iteration where we reach the normal time *
* allocation, Crafty will continue to search. Previously the score *
* had to drop by 1/4 pawn, but cluster testing has shown that this *
* change is better. Final bit of old rotated bitboard logic *
* removed. We had two bitboards, RooksQueens and BishopsQueens *
* that were updated in MakeMove() and UnmakeMove(). It turned out *
* to be faster to just OR the needed piece bitboards together since *
* they were infrequently used in the new "magic" approach, which *
* allowed me to remove them completely from the position structure *
* and make/unmake. Net result was a percent or two faster search *
* overall. Old bug fixed related to EGTB usage. The Edwards *
* format did not include en passant pawn captures, so it was *
* necessary to avoid probing any position where both sides had a *
* pawn and there was any possibility of an en passant capture (one *
* pawn on original square, enemy pawn anywhere on either adjacent *
* file). The Nalimov tables consider en passant correctly, but *
* somehow this old code was either left in iterate.c or else added *
* back in by accident. It is now no longer present. Minor changes *
* (suggested by J. Cleveland on CCC) that avoids trying a null-move *
* search when remaining depth == 1, and which saves some effort by *
* remembering, when a node fails low, the first move searched. *
* This move then gets stored in the hash table as the "best move". *
* While this might be wrong, it has a chance of being right and *
* when it is good enough to cause a cutoff, we can avoid a move *
* generation which saves a bit of time. Fixed a significant bug in *
* EvaluateWinningChances() where it was using a global variable *
* "wtm" which tells who is to move in the real game, not at the *
* current position in the treee. This value is used for tempo *
* calculations to determine if the losing king (in a K + rook-pawn *
* ending (with or without wrong bishop)) can reach the queening *
* square before the winning side's king can block acccess. This *
* would randomly make the tempo calculation off by one, so that the *
* score could bounce from draw to win and back as the game *
* progresses, since about 1/2 the time the wtm value is wrong. I *
* simply passed the current wtm in as a formal parameter to solve *
* this (a good example of why having a global variable and a formal *
* argument paramenter using the same name is a bad idea.) In this *
* same general area, EvaluateDraws() could set the score to *
* DrawScore, which was somewhat "iffy". I changed this to simply *
* determine if the side that ahead is score has any realistic *
* winning chances. If not, I divide the score by 10 rather than *
* setting it to the absolute drawscore. This has the same effect, *
* but does let the evaluation guide the search to better moves when *
* it is convinced all of them lead to draws. This version is about *
* +100 Elo stronger than 23.0 based on cluster testing results. *
* *
* 23.2 Two changes related to draw handling. First, the 50-move draw *
* rule is tricky. It is possible that the move on the 100th ply *
* after the last non-reversible move might not be a draw, even if *
* it is reversible itself, because it might deliver mate. In this *
* specific case, the mate will end the game as a win. This has *
* been fixed in Crafty to match this specific rule exception. Also *
* draws by "insufficient material" have been changed to match the *
* FIDE rules which say that mate can't be possible, even with worst *
* possible play by the opponent. Crafty would claim a draw in a *
* simple KN vs KN position, which is incorrect. Even though *
* neither side can force mate, mate is possible and so the position *
* is not a draw by FIDE rules. Mobility scoring changed for *
* sliding pieces. Now the mobility scores are pre-computed and *
* stored in a table that is addressed by the "magic number move *
* generation idea". This completely eliminates the computational *
* cost of the mobility scoring since all of the scores are pre- *
* computed before the game starts. This was a modest speed *
* improvement but really made the code simpler and smaller. Change *
* to lazy eval cutoff code to improve accuracy. BookUP() had a *
* minor bug that caused it to not report how many moves were not *
* included because of the "maxply" limit. This has been fixed also *
* so that it now reports the correct value. New xboard "cores" and *
* "memory" command support added. Code to malloc() both was also *
* rewritten completely to clean it up and simplify things. In an *
* effort to avoid confusion, there is one caveat here. If your *
* .craftyrc/crafty.rc file has an option to set the number of *
* threads (mt=n/smpnt=n), then the "cores" option from xboard is *
* automatically disabled so that the .craftyrc option effectively *
* overrides any potential cores setting. If you set hash or hashp *
* in the .craftyrc/crafty.rc file, then the "memory" option from *
* xboard is automatically disabled, for the same reason. In short, *
* you can let xboard set the number of threads and memory usage *
* limit, or you can set them in your .craftyrc/crafty.rc file. But *
* if you use the .craftyrc/crafty.rc file to set either, then the *
* corresponding xboard command will be disabled. *
* *
* 23.3 Null-move search restriction changed to allow null-move searches *
* at any node where the side on move has at least one piece of any *
* type. Minor bug in ValidMove() fixed to catch "backward" pawn *
* moves and flag them as illegal. This sometimes caused an error *
* when annotating games and annotating for both sides. The killer *
* move array could have "backward" moves due to flipping sides back *
* and forth, which would cause some odd PV displays. Small change *
* to "reduce-at-root". We no longer reduce moves that are flagged *
* as "do not search in parallel". Check extension modified so that *
* if "SEE" says the check is unsafe, the extension is not done. We *
* found this to be worth about +10 Elo. We also now reduce any *
* capture move that appears in the "REMAINING_MOVES" phase since *
* they can only appear there if SEE returns a score indicating loss *
* of material. We now reduce a bit more aggressively, reducing by` *
* 2 plies once we have searched at least 4 moves at any ply. I *
* tried going to 3 on very late moves, but could not find any case *
* where this was better, even limiting it to near the root or other *
* ideas. But reducing by 2 plies after the at least 2 moves are *
* searched was an improvement. Minor change is that the first move *
* is never reduced. It is possible that there is no hash move, no *
* non-losing capture, and no killer move. That drops us into the *
* REMAINING_MOVES phase which could reduce the first move searched, *
* which was not intended. Very minor tweak, but a tweak all the *
* same. *
* *
* 23.4 Bug in hash implementation fixed. It was possible to get a hash *
* hit at ply=2, and alter the ply=1 PV when it should be left with *
* no change. This could cause Crafty to display one move as best *
* and play another move entirely. Usually this move was OK, but it *
* could, on occasion, be an outright blunder. This has been fixed. *
* The search.c code has been re-written to eliminate SearchRoot() *
* entirely, which simplifies the code. The only duplication is in *
* SearchParallel() which would be messier to eliminate. Ditto for *
* quiesce.c, which now only has Quiesce() and QuiesceEvasions(). *
* The old QuiesceChecks() has been combined with Quiesce, again to *
* eliminate duplication and simplify the code. Stupid bug in code *
* that handles time-out. One place checked the wrong variable and *
* could cause a thread to attempt to output a PV after the search *
* was in the process of timing out. That thread could back up an *
* incomplete/bogus search result to the root in rare occasions, *
* which would / could result in Crafty kibitzing one move but *
* playing a different move. On occasion, the move played could be *
* a horrible blunder. Minor bug caused HashStore() to lose a best *
* move when overwriting an old position with a null-move search *
* result. Minor change by Tracy to lazy evaluation cutoff to speed *
* up evaluation somewhat. Old "Trojan Horse" attack detection was *
* removed. At today's depths, it was no longer needed. New hash *
* idea stores the PV for an EXACT hash entry in a separate hash *
* table. When an EXACT hit happens, this PV can be added to the *
* incomplete PV we have so far so that we have the exact path that *
* leads to the backed up score. New "phash" (path hash) command to *
* set the number of entries in this path hash table. For longer *
* searches, a larger table avoids path table collisions which will *
* produce those short paths that end in <HT>. If <HT> appears in *
* too many PVs, phash should be increased. The "Trojan Horse" code *
* has been completely removed, which also resulted in the removal *
* of the last bit of "pre-processing code" in preeval.c, so it has *
* been completely removed as well. Current search depths are such *
* that the Trojan Horse code is simply not needed any longer. A *
* minor bug in TimeSet() fixed where on rare occasions, near the *
* end of a time control, time_limit could be larger than the max *
* time allowed (absolute_time_limit). We never check against this *
* limit until we exceed the nominal time limit. Cleanup on the *
* draw by repetition code to greatly simplify the code as well as *
* speed it up. *
* *
*******************************************************************************
*/
************************************************************
* *
* First, parse the command-line options and pick off the *
* ones that need to be handled before any initialization *
* is attempted (mainly path commands at present.) *
* *
************************************************************
*/
************************************************************
* *
* Now, read the crafty.rc/.craftyrc initialization file *
* and process the commands that need to be handled prior *
* to initializing things (path commands). *
* *
************************************************************
*/
************************************************************
* *
* If NUMA is enabled, report on the current machine *
* configuration. *
* *
************************************************************
*/
************************************************************
* *
* Initialize chess board to starting position. *
* *
************************************************************
*/
************************************************************
* *
* Now, parse the command-line options and pick off the *
* ones that need to be handled after initialization is *
* completed. *
* *
************************************************************
*/
************************************************************
* *
* From this point forward, we are in a state where it is *
* *
* O P P O N E N T ' S turn to move. *
* *
************************************************************
*/
************************************************************
* *
* Next, read the crafty.rc/.craftyrc initialization file *
* and process the commands that need to be handled after *
* engine initialization has been completed. *
* *
************************************************************
*/
************************************************************
* *
* Check to see if we can find a "crafty.cpf" personality *
* file which contains the default personality settings *
* to be used unless overridden by the user. *
* *
************************************************************
*/
************************************************************
* *
* This is the "main loop" that never ends unless the *
* user tells Crafty to "quit". We read commands/moves *
* execute them, and when a move is entered we change *
* sides and execute a search to find a reply. We repeat *
* this until the game ends or the opponent gets tired *
* and tells us to terminate the engine. *
* *
* Prompt user and read input string for processing. As *
* long as Option() returns a non-zero value, continue *
* reading lines and calling Option(). When Option() *
* fails to recogize a command, then try InputMove() to *
* determine if this is a legal move. *
* *
* While we are waiting on a move, we call Ponder() which *
* will find a move that it assumes the opponent will *
* make, and then it will call Iterate() to find a reply *
* for that move while we are waiting to see what is *
* actually played in the game. Ponder() will return one *
* of the following "results" (stored in "presult"): *
* *
* (0) This indicates that Ponder() did not run, either *
* because pondering is disabled, or we are not in a *
* state where pondering is allowed, such as using *
* the xboard "force" command to set up a game that *
* will be continued. *
* *
* (1) This indicates that we pondered a move, the *
* opponent actually played this move, and we were *
* able to complete a normal search for the proper *
* amount of time and have a move ready to use. *
* *
* (2) This indicates that we pondered a move, but that *
* for some reason, we did not need to continue until *
* time ran out. For example, we found a forced mate *
* and further searching is not needed. The search *
* is not "in progress" but we still have a valid *
* move to play here. *
* *
* (3) We pondered, but the opponent either played a *
* different move, or else entered a command that *
* forces us to unwind the search so that the command *
* can be executed. In this case, we will re-start *
* pondering, otherwise we make the correct move and *
* then start a normal search. *
* *
************************************************************
*/
************************************************************
* *
* We have a move. Make the move (returned by InputMove) *
* and then change the side on move (wtm). *
* *
************************************************************
*/
************************************************************
* *
* From this point forward, we are in a state where it is *
* *
* C R A F T Y ' S turn to move. *
* *
************************************************************
*/
************************************************************
* *
* We have made the indicated move, before we do a search *
* we need to determine if the present position is a draw *
* by rule. If so, Crafty allowed it to happen and must *
* be satisfied with a draw, so we will claim it and end *
* the current game. *
* *
************************************************************
*/
************************************************************
* *
* Now call Iterate() to compute a move for the current *
* position. (Note this is not done if Ponder() has al- *
* ready computed a move.) *
* *
************************************************************
*/
************************************************************
* *
* We've now completed a search and need to handle a *
* pending draw offer based on what the search found. *
* *
* When we get a draw offer, we make a note, but we do *
* not accept it until after we have a chance to see what *
* happens after making the opponent's move that came *
* with the draw offer. If he played a blunder, we are *
* not going to mistakenly accept a draw when we are now *
* winning. *
* *
************************************************************
*/
************************************************************
* *
* We've now completed a search and need to do some basic *
* bookkeeping. *
* *
************************************************************
*/
************************************************************
* *
* If the last_pv.path is null, then we were either *
* checkmated or stalemated. We need to determine which *
* and end the game appropriately. *
* *
* If we do have a PV, we will also check to see if it *
* leads to mate and make the proper announcement if so. *
* *
************************************************************
*/
************************************************************
* *
* See if we want to offer a draw based on the recent *
* scores that have been returned. See resign.c for more *
* details, but this is where we offer a draw, or resign, *
* if appropriate. This has nothing to do with claiming *
* a draw by rule, which is done later. *
* *
************************************************************
*/
************************************************************
* *
* Now output the move chosen by the search, and the *
* "result" string if this move checkmates our opponent. *
* *
************************************************************
*/
************************************************************
* *
* From this point forward, we are in a state where it is *
* *
* O P P O N E N T ' S turn to move. *
* *
* We have made the indicated move, we need to determine *
* if the present position is a draw by rule. If so, we *
* need to send the appropriate game result to xboard *
* and/or inform the operator/opponent. *
* *
************************************************************
*/
************************************************************
* *
* Save the ponder_move from the current principal *
* variation, then shift it left two moves to use as the *
* starting point for the next search. Adjust the depth *
* to start the next search at the right iteration. *
* *
************************************************************
*/
************************************************************
* *
* Now execute LearnValue() to record the scores for the *
* first N searches out of book. see learn.c for details *
* on how this is used and when. *
* *
************************************************************
*/
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