dlaqsy (l)  Linux Man Pages
dlaqsy: equilibrates a symmetric matrix A using the scaling factors in the vector S
NAME
DLAQSY  equilibrates a symmetric matrix A using the scaling factors in the vector SSYNOPSIS
 SUBROUTINE DLAQSY(
 UPLO, N, A, LDA, S, SCOND, AMAX, EQUED )
 CHARACTER EQUED, UPLO
 INTEGER LDA, N
 DOUBLE PRECISION AMAX, SCOND
 DOUBLE PRECISION A( LDA, * ), S( * )
PURPOSE
DLAQSY equilibrates a symmetric matrix A using the scaling factors in the vector S.ARGUMENTS
 UPLO (input) CHARACTER*1

Specifies whether the upper or lower triangular part of the
symmetric matrix A is stored.
= aqUaq: Upper triangular
= aqLaq: Lower triangular  N (input) INTEGER
 The order of the matrix A. N >= 0.
 A (input/output) DOUBLE PRECISION array, dimension (LDA,N)
 On entry, the symmetric matrix A. If UPLO = aqUaq, 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 = aqLaq, 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 = aqYaq, the equilibrated matrix: diag(S) * A * diag(S).
 LDA (input) INTEGER
 The leading dimension of the array A. LDA >= max(N,1).
 S (input) DOUBLE PRECISION array, dimension (N)
 The scale factors for A.
 SCOND (input) DOUBLE PRECISION
 Ratio of the smallest S(i) to the largest S(i).
 AMAX (input) DOUBLE PRECISION
 Absolute value of largest matrix entry.
 EQUED (output) CHARACTER*1

Specifies whether or not equilibration was done.
= aqNaq: No equilibration.
= aqYaq: Equilibration was done, i.e., A has been replaced by diag(S) * A * diag(S).
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.