numeric-linalg

Educational material on the SciPy implementation of numerical linear algebra algorithms

Name	Size	Mode
..
lapack/SRC/ilaenv2stage.f	5756B	-rw-r--r--

*> \brief \b ILAENV2STAGE
*
*  =========== DOCUMENTATION ===========
*
* Online html documentation available at
*            http://www.netlib.org/lapack/explore-html/
*
*> \htmlonly
*> Download ILAENV2STAGE + dependencies
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.tgz?format=tgz&filename=/lapack/lapack_routine/ilaenv2stage.f">
*> [TGZ]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.zip?format=zip&filename=/lapack/lapack_routine/ilaenv2stage.f">
*> [ZIP]</a>
*> <a href="http://www.netlib.org/cgi-bin/netlibfiles.txt?format=txt&filename=/lapack/lapack_routine/ilaenv2stage.f">
*> [TXT]</a>
*> \endhtmlonly
*
*  Definition:
*  ===========
*
*       INTEGER FUNCTION ILAENV2STAGE( ISPEC, NAME, OPTS, N1, N2, N3, N4 )
*
*       .. Scalar Arguments ..
*       CHARACTER*( * )    NAME, OPTS
*       INTEGER            ISPEC, N1, N2, N3, N4
*       ..
*
*
*> \par Purpose:
*  =============
*>
*> \verbatim
*>
*> ILAENV2STAGE is called from the LAPACK routines to choose problem-dependent
*> parameters for the local environment.  See ISPEC for a description of
*> the parameters.
*> It sets problem and machine dependent parameters useful for *_2STAGE and
*> related subroutines.
*>
*> ILAENV2STAGE returns an INTEGER
*> if ILAENV2STAGE >= 0: ILAENV2STAGE returns the value of the parameter
*>                       specified by ISPEC
*> if ILAENV2STAGE < 0:  if ILAENV2STAGE = -k, the k-th argument had an
*>                       illegal value.
*>
*> This version provides a set of parameters which should give good,
*> but not optimal, performance on many of the currently available
*> computers for the 2-stage solvers. Users are encouraged to modify this
*> subroutine to set the tuning parameters for their particular machine using
*> the option and problem size information in the arguments.
*>
*> This routine will not function correctly if it is converted to all
*> lower case.  Converting it to all upper case is allowed.
*> \endverbatim
*
*  Arguments:
*  ==========
*
*> \param[in] ISPEC
*> \verbatim
*>          ISPEC is INTEGER
*>          Specifies the parameter to be returned as the value of
*>          ILAENV2STAGE.
*>          = 1: the optimal blocksize nb for the reduction to BAND
*>
*>          = 2: the optimal blocksize ib for the eigenvectors
*>               singular vectors update routine
*>
*>          = 3: The length of the array that store the Housholder
*>               representation for the second stage
*>               Band to Tridiagonal or Bidiagonal
*>
*>          = 4: The workspace needed for the routine in input.
*>
*>          = 5: For future release.
*> \endverbatim
*>
*> \param[in] NAME
*> \verbatim
*>          NAME is CHARACTER*(*)
*>          The name of the calling subroutine, in either upper case or
*>          lower case.
*> \endverbatim
*>
*> \param[in] OPTS
*> \verbatim
*>          OPTS is CHARACTER*(*)
*>          The character options to the subroutine NAME, concatenated
*>          into a single character string.  For example, UPLO = 'U',
*>          TRANS = 'T', and DIAG = 'N' for a triangular routine would
*>          be specified as OPTS = 'UTN'.
*> \endverbatim
*>
*> \param[in] N1
*> \verbatim
*>          N1 is INTEGER
*> \endverbatim
*>
*> \param[in] N2
*> \verbatim
*>          N2 is INTEGER
*> \endverbatim
*>
*> \param[in] N3
*> \verbatim
*>          N3 is INTEGER
*> \endverbatim
*>
*> \param[in] N4
*> \verbatim
*>          N4 is INTEGER
*>          Problem dimensions for the subroutine NAME; these may not all
*>          be required.
*> \endverbatim
*
*  Authors:
*  ========
*
*> \author Univ. of Tennessee
*> \author Univ. of California Berkeley
*> \author Univ. of Colorado Denver
*> \author NAG Ltd.
*> \author Nick R. Papior
*
*> \ingroup ilaenv2stage
*
*> \par Further Details:
*  =====================
*>
*> \verbatim
*>
*>  The following conventions have been used when calling ILAENV2STAGE
*> from the LAPACK routines:
*>  1)  OPTS is a concatenation of all of the character options to
*>      subroutine NAME, in the same order that they appear in the
*>      argument list for NAME, even if they are not used in determining
*>      the value of the parameter specified by ISPEC.
*>  2)  The problem dimensions N1, N2, N3, N4 are specified in the order
*>      that they appear in the argument list for NAME.  N1 is used
*>      first, N2 second, and so on, and unused problem dimensions are
*>      passed a value of -1.
*>  3)  The parameter value returned by ILAENV2STAGE is checked for validity in
*>      the calling subroutine.
*>
*> \endverbatim
*>
*  =====================================================================
      INTEGER FUNCTION ILAENV2STAGE( ISPEC, NAME, OPTS, N1, N2, N3,
     $                               N4 )
*
*  -- LAPACK auxiliary routine --
*  -- LAPACK is a software package provided by Univ. of Tennessee,    --
*  -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..--
*     July 2017
*
*     .. Scalar Arguments ..
      CHARACTER*( * )    NAME, OPTS
      INTEGER            ISPEC, N1, N2, N3, N4
*     ..
*
*  =====================================================================
*     ..
*     .. Local Scalars ..
      INTEGER            IISPEC
*     ..
*     .. External Functions ..
      INTEGER            IPARAM2STAGE
      EXTERNAL           IPARAM2STAGE
*     ..
*     .. Executable Statements ..
*
      GO TO ( 10, 10, 10, 10, 10 )ISPEC
*
*     Invalid value for ISPEC
*
      ILAENV2STAGE = -1
      RETURN
*
   10 CONTINUE
*
*     2stage eigenvalues and SVD or related subroutines.
*
      IISPEC = 16 + ISPEC
      ILAENV2STAGE = IPARAM2STAGE( IISPEC, NAME, OPTS,
     $                             N1, N2, N3, N4 )
      RETURN
*
*     End of ILAENV2STAGE
*
      END