dlaqsy-f(3)

dlaqsy.f –

Synopsis

Functions/Subroutines

subroutine dlaqsy (UPLO, N, A, LDA, S, SCOND, AMAX, EQUED)
DLAQSY scales a symmetric/Hermitian matrix, using scaling factors computed by spoequ.

Function/Subroutine Documentation

subroutine dlaqsy (characterUPLO, integerN, double precision, dimension( lda, * )A, integerLDA, double precision, dimension( * )S, double precisionSCOND, double precisionAMAX, characterEQUED)

DLAQSY scales a symmetric/Hermitian matrix, using scaling factors computed by spoequ.

Purpose:

 DLAQSY equilibrates a symmetric matrix A using the scaling factors
 in the vector S.

Parameters:

UPLO

 UPLO is CHARACTER*1
 Specifies whether the upper or lower triangular part of the
 symmetric matrix A is stored.
 = 'U': Upper triangular
 = 'L': Lower triangular

 N is INTEGER
 The order of the matrix A. N >= 0.

 A is DOUBLE PRECISION array, dimension (LDA,N)
 On entry, the symmetric matrix A. If UPLO = 'U', the leading
 n by n upper triangular part of A contains the upper
 triangular part of the matrix A, and the strictly lower
 triangular part of A is not referenced. If UPLO = 'L', the
 leading n by n lower triangular part of A contains the lower
 triangular part of the matrix A, and the strictly upper
 triangular part of A is not referenced.
 On exit, if EQUED = 'Y', the equilibrated matrix:
 diag(S) * A * diag(S).

LDA

 LDA is INTEGER
 The leading dimension of the array A. LDA >= max(N,1).

 S is DOUBLE PRECISION array, dimension (N)
 The scale factors for A.

SCOND

 SCOND is DOUBLE PRECISION
 Ratio of the smallest S(i) to the largest S(i).

AMAX

 AMAX is DOUBLE PRECISION
 Absolute value of largest matrix entry.

EQUED

 EQUED is CHARACTER*1
 Specifies whether or not equilibration was done.
 = 'N': No equilibration.
 = 'Y': Equilibration was done, i.e., A has been replaced by
 diag(S) * A * diag(S).

Internal Parameters:

 THRESH is a threshold value used to decide if scaling should be done
 based on the ratio of the scaling factors. If SCOND < THRESH,
 scaling is done.
 LARGE and SMALL are threshold values used to decide if scaling should
 be done based on the absolute size of the largest matrix element.
 If AMAX > LARGE or AMAX < SMALL, scaling is done.

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Definition at line 134 of file dlaqsy.f.

Author

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