Provided by: liblapack-doc_3.3.1-1_all NAME

LAPACK-3 - equilibrates a symmetric matrix A using the scaling factors in the vector S

SYNOPSIS

SUBROUTINE SLAQSP( UPLO, N, AP, S, SCOND, AMAX, EQUED )

CHARACTER      EQUED, UPLO

INTEGER        N

REAL           AMAX, SCOND

REAL           AP( * ), S( * )

PURPOSE

SLAQSP 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.

AP      (input/output) REAL array, dimension (N*(N+1)/2)
On entry, the upper or lower triangle of the symmetric 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= 'Y':  Equilibration was done, i.e., A has been replaced by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 auxiliary routine (version 3.2)     April 2011                            SLAQSP(3lapack)