khstd.cc

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/****************************************
*  Computer Algebra System SINGULAR     *
****************************************/
/*
* ABSTRACT:utils for hilbert driven kStd
*/
 
#include "kernel/mod2.h"
 
#include "misc/options.h"
#include "misc/intvec.h"
 
#include "polys/simpleideals.h"
 
#include "kernel/combinatorics/stairc.h"
#include "kernel/combinatorics/hilb.h"
 
#include "kernel/GBEngine/kutil.h"
#include "kernel/GBEngine/kstd1.h"
#include "kernel/GBEngine/khstd.h"
 
#include "kernel/polys.h"
 
/*2
* compare the given hilbert series with the current one,
* delete not needed pairs (if possible)
*/
void khCheck( ideal Q, intvec *w, intvec *hilb, int &eledeg, int &count,
              kStrategy strat)
  /* ideal S=strat->Shdl, poly p=strat->P.p */
/*
* compute the number eledeg of elements with a degree >= deg(p) going into kStd,
* p is already in S and for all further q going into S yields deg(q) >= deg(p),
* the real computation is only done if the degree has changed,
* then we have eledeg == 0 on this degree and we make:
*   - compute the Hilbert series newhilb from S
*     (hilb is the final Hilbert series)
*   - in module case: check that all comp up to strat->ak are used
*   - compute the eledeg from newhilb-hilb for the first degree deg with
*     newhilb-hilb != 0
*     (Remark: consider the Hilbert series with coeff. up to infinity)
*   - clear the set L for degree < deg
* the number count is only for statistics (in the caller initialise count = 0),
* in order to get a first computation, initialise eledeg = 1 in the caller.
* The weights w are needed in the module case, otherwise NULL.
*/
{
  intvec *newhilb,*new1;
  int deg,l,ln,mw;
  pFDegProc degp;
 
  eledeg--;
  if (eledeg == 0)
  {
    if (strat->ak>0)
    {
      char *used_comp=(char*)omAlloc0(strat->ak+1);
      int i;
      for(i=strat->sl;i>0;i--)
      {
        used_comp[pGetComp(strat->S[i])]='\1';
      }
      for(i=strat->ak;i>0;i--)
      {
        if(used_comp[i]=='\0')
        {
          omFree((ADDRESS)used_comp);
          return;
        }
      }
      omFree((ADDRESS)used_comp);
    }
    degp=currRing->pFDeg;
    // if weights for variables were given to std computations,
    // then pFDeg == degp == kHomModDeg (see kStd)
    if ((degp!=kModDeg) && (degp!=kHomModDeg)) degp=p_Totaldegree;
    // degp = pWDegree;
    l = hilb->length()-1;
    mw = (*hilb)[l];
    newhilb =hFirstSeries(strat->Shdl,w,Q,strat->kHomW);
    ln = newhilb->length()-1;
    deg = degp(strat->P.p,currRing)-mw;
    loop // compare the series in degree deg, try to increase deg -----------
    {
      if (deg < ln) // deg may be out of range
      {
        if (deg < l)
          eledeg = (*newhilb)[deg]-(*hilb)[deg];
        else
          eledeg = (*newhilb)[deg];
      }
      else
      {
        if (deg < l)
          eledeg = -(*hilb)[deg];
        else // we have newhilb = hilb
        {
          while (strat->Ll>=0)
          {
            count++;
            if(TEST_OPT_PROT)
            {
              PrintS("h");
              mflush();
            }
            deleteInL(strat->L,&strat->Ll,strat->Ll,strat);
          }
          delete newhilb;
          return;
        }
      }
      if (eledeg > 0) // elements to delete
        break;
      else if (eledeg <0) // strange....see bug_43
        return;
      deg++;
    } /* loop */
    delete newhilb;
    while ((strat->Ll>=0) && (degp(strat->L[strat->Ll].p,currRing)-mw < deg)) // the essential step
    {
      count++;
      if(TEST_OPT_PROT)
      {
        PrintS("h");
        mflush();
      }
      deleteInL(strat->L,&strat->Ll,strat->Ll,strat);
    }
  }
}
 
 
void khCheckLocInhom(ideal Q, intvec *w, intvec *hilb, int &count,
             kStrategy strat)
 
/*
This will be used for the local orderings in the case of the inhomogeneous ideals.
Assume f1,...,fs are already in the standard basis. Test if hilb(LM(f1),...,LM(fs),1)
is equal to the inputted one.
If no, do nothing.
If Yes, we know that all polys that we need are already in the standard basis
so delete all the remaining pairs
*/
{
  ideal Lm;
  intvec *newhilb,*new1;
 
  Lm = id_Head(strat->Shdl,currRing);
 
  newhilb =hFirstSeries(Lm,w,Q,strat->kHomW);
 
  if(newhilb->compare(hilb) == 0)
  {
    while (strat->Ll>=0)
    {
      count++;
      if(TEST_OPT_PROT)
      {
        PrintS("h");
        mflush();
      }
      deleteInL(strat->L,&strat->Ll,strat->Ll,strat);
    }
    delete newhilb;
    return;
  }
  id_Delete(&Lm,currRing);
}