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LAPACK 3.11.0
LAPACK: Linear Algebra PACKage
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LAPACK 3.11.0
LAPACK: Linear Algebra PACKage
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| subroutine xlaenv | ( | integer | ISPEC, |
| integer | NVALUE | ||
| ) |
XLAENV
XLAENV sets certain machine- and problem-dependent quantities which will later be retrieved by ILAENV.
| [in] | ISPEC | ISPEC is INTEGER
Specifies the parameter to be set in the COMMON array IPARMS.
= 1: the optimal blocksize; if this value is 1, an unblocked
algorithm will give the best performance.
= 2: the minimum block size for which the block routine
should be used; if the usable block size is less than
this value, an unblocked routine should be used.
= 3: the crossover point (in a block routine, for N less
than this value, an unblocked routine should be used)
= 4: the number of shifts, used in the nonsymmetric
eigenvalue routines
= 5: the minimum column dimension for blocking to be used;
rectangular blocks must have dimension at least k by m,
where k is given by ILAENV(2,...) and m by ILAENV(5,...)
= 6: the crossover point for the SVD (when reducing an m by n
matrix to bidiagonal form, if max(m,n)/min(m,n) exceeds
this value, a QR factorization is used first to reduce
the matrix to a triangular form)
= 7: the number of processors
= 8: another crossover point, for the multishift QR and QZ
methods for nonsymmetric eigenvalue problems.
= 9: maximum size of the subproblems at the bottom of the
computation tree in the divide-and-conquer algorithm
(used by xGELSD and xGESDD)
=10: ieee NaN arithmetic can be trusted not to trap
=11: infinity arithmetic can be trusted not to trap |
| [in] | NVALUE | NVALUE is INTEGER
The value of the parameter specified by ISPEC. |
1.9.4