ilaenv2stage(3)

NAME
ilaenv2stage - ilaenv2stage: tuning parameters for 2-stage eig

SYNOPSIS

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

Detailed Description

Function 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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