SRC/ilaenv2stage.f(3)      Library Functions Manual      SRC/ilaenv2stage.f(3)

NAME
       SRC/ilaenv2stage.f

SYNOPSIS
   Functions/Subroutines
       integer function ilaenv2stage (ispec, name, opts, n1, n2, n3, n4)
           ILAENV2STAGE

Function/Subroutine Documentation
   integer function ilaenv2stage (integer ispec, character*( * ) name,
       character*( * ) opts, integer n1, integer n2, integer n3, integer n4)
       ILAENV2STAGE

       Purpose:


           !>
           !> 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.
           !>

       Parameters
           ISPEC

           !>          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.
           !>

           NAME

           !>          NAME is CHARACTER*(*)
           !>          The name of the calling subroutine, in either upper case or
           !>          lower case.
           !>

           OPTS

           !>          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'.
           !>

           N1

           !>          N1 is INTEGER
           !>

           N2

           !>          N2 is INTEGER
           !>

           N3

           !>          N3 is INTEGER
           !>

           N4

           !>          N4 is INTEGER
           !>          Problem dimensions for the subroutine NAME; these may not all
           !>          be required.
           !>

       Author
           Univ. of Tennessee


           Univ. of California Berkeley


           Univ. of Colorado Denver


           NAG Ltd.


           Nick R. Papior

       Further Details:


           !>
           !>  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.
           !>
           !>

       Definition at line 148 of file ilaenv2stage.f.

Author
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LAPACK                          Version 3.12.0           SRC/ilaenv2stage.f(3)