dlaqsy(3F)

NAME
     DLAQSY - equilibrate a symmetric matrix A using the scaling factors in
     the vector S

SYNOPSIS
     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.  = 'U':  Upper triangular
             = 'L':  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 = '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     (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.  = 'N':  No
             equilibration.
             = 'Y':  Equilibration was done, i.e., A has been replaced by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.