Man page - ilaenv2stage(3)

Packages contains this manual

Manual

ilaenv2stage

NAME
SYNOPSIS
Functions
Detailed Description
Function Documentation
integer function ilaenv2stage (integer ispec, character*( * ) name,character*( * ) opts, integer n1, integer n2, integer n3, integer n4)
Author

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.

Author

Generated automatically by Doxygen for LAPACK from the source code.