DLAQSP (3) Linux Manual Page

dlaqsp.f –

Synopsis

Functions/Subroutines

subroutine dlaqsp (UPLO, N, AP, S, SCOND, AMAX, EQUED)
DLAQSP scales a symmetric/Hermitian matrix in packed storage, using scaling factors computed by sppequ.

Function/Subroutine Documentation

subroutine dlaqsp (characterUPLO, integerN, double precision, dimension( * )AP, double precision, dimension( * )S, double precisionSCOND, double precisionAMAX, characterEQUED)

DLAQSP scales a symmetric/Hermitian matrix in packed storage, using scaling factors computed by sppequ.

Purpose:

 DLAQSP equilibrates a symmetric matrix A using the scaling factors

 in the vector S.

 

Parameters:

UPLO

 UPLO is CHARACTER*1

 Specifies whether the upper or lower triangular part of the

 symmetric matrix A is stored.

 = ‘U’: Upper triangular

 = ‘L’: Lower triangular

N

 N is INTEGER

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

AP

 AP is DOUBLE PRECISION 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

 S is DOUBLE PRECISION array, dimension (N)

 The scale factors for A.

SCOND

 SCOND is DOUBLE PRECISION

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

AMAX

 AMAX is DOUBLE PRECISION

 Absolute value of largest matrix entry.

EQUED

 EQUED is 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 = ‘Y’: Equilibration was done, i.e., A has been replaced by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).

 

Internal 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.

 

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Definition at line 126 of file dlaqsp.f.

Author

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