dlaqsy man page on Scientific

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DLAQSY(1)	    LAPACK auxiliary routine (version 3.2)	     DLAQSY(1)

NAME
       DLAQSY - equilibrates 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	       = 'Y':  Equilibration was done, i.e., A has  been  replaced  by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 scal‐
       ing should be done based on the absolute size  of  the  largest	matrix
       element.	 If AMAX > LARGE or AMAX < SMALL, scaling is done.

 LAPACK auxiliary routine (versioNovember 2008			     DLAQSY(1)
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