xlaenv.f

Go to the documentation of this file.

*> \brief \b XLAENV
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at
*            http://www.netlib.org/lapack/explore-html/
*
*  Definition:
*  ===========
*
*       SUBROUTINE XLAENV( ISPEC, NVALUE )
*
*       .. Scalar Arguments ..
*       INTEGER            ISPEC, NVALUE
*       ..
*
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> XLAENV sets certain machine- and problem-dependent quantities
*> which will later be retrieved by ILAENV.
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] ISPEC
*> \verbatim
*>          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
*> \endverbatim
*>
*> \param[in] NVALUE
*> \verbatim
*>          NVALUE is INTEGER
*>          The value of the parameter specified by ISPEC.
*> \endverbatim
*
*  Authors:
*  ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*
*> \ingroup aux_lin
*
*  =====================================================================
      SUBROUTINE xlaenv( ISPEC, NVALUE )
*
*  -- LAPACK test routine --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*
*     .. Scalar Arguments ..
      INTEGER            ISPEC, NVALUE
*     ..
*
*  =====================================================================
*
*     .. Arrays in Common ..
      INTEGER            IPARMS( 100 )
*     ..
*     .. Common blocks ..
      COMMON             / claenv / iparms
*     ..
*     .. Save statement ..
      SAVE               / claenv /
*     ..
*     .. Executable Statements ..
*
      IF( ispec.GE.1 .AND. ispec.LE.9 ) THEN
         iparms( ispec ) = nvalue
      END IF
*
      RETURN
*
*     End of XLAENV
*
      END