claqsp(3)

NAME

CLAQSP - equilibrate a symmetric matrix A using the scal

ing factors in the vector S

SYNOPSIS

SUBROUTINE CLAQSP( UPLO, N, AP, S, SCOND, AMAX, EQUED )
    CHARACTER      EQUED, UPLO
    INTEGER        N
    REAL           AMAX, SCOND
    REAL           S( * )
    COMPLEX        AP( * )

PURPOSE

CLAQSP 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 triangu

lar
= 'L': Lower triangular

N (input) INTEGER

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

AP (input/output) COMPLEX array, dimension

(N*(N+1)/2)

On entry, the upper or lower triangle of the sym

metric matrix A, packed columnwise in a linear array. The j-th

column of A is stored in the array AP as follows: if UPLO = 'U',

AP(i + (j-1)*j/2) = A(i,j) for 1<=i<=j; if UPLO = 'L', AP(i +

(j-1)*(2n-j)/2) = A(i,j) for j<=i<=n.

On exit, the equilibrated matrix: diag(S) * A *

diag(S), in the same storage format as A.

S (input) REAL array, dimension (N)

The scale factors for A.

SCOND (input) REAL

Ratio of the smallest S(i) to the largest S(i).

AMAX (input) REAL

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.

LAPACK version 3.0 15 June 2000

CLAQSP(3)