---
name: "claqsp"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/claqsp/3lapack"
---

# claqsp(3lapack)

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

## NAME

CLAQSP - equilibrates a symmetric matrix A using the scaling 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 triangular\
   \= '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 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   \= 'Y':  Equilibration was done, i.e., A has been replaced by diag(S) \* A \* diag(S).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.