cheequb (l)  Linux Man Pages
cheequb: computes row and column scalings intended to equilibrate a symmetric matrix A and reduce its condition number (with respect to the twonorm)
Command to display cheequb
manual in Linux: $ man l cheequb
NAME
CHEEQUB  computes row and column scalings intended to equilibrate a symmetric matrix A and reduce its condition number (with respect to the twonorm)
SYNOPSIS
 SUBROUTINE CHEEQUB(

UPLO, N, A, LDA, S, SCOND, AMAX, WORK, INFO )

IMPLICIT
NONE

INTEGER
INFO, LDA, N

REAL
AMAX, SCOND

CHARACTER
UPLO

COMPLEX
A( LDA, * ), WORK( * )

REAL
S( * )
PURPOSE
CSYEQUB computes row and column scalings intended to equilibrate a
symmetric matrix A and reduce its condition number
(with respect to the twonorm). S contains the scale factors,
S(i) = 1/sqrt(A(i,i)), chosen so that the scaled matrix B with
elements B(i,j) = S(i)*A(i,j)*S(j) has ones on the diagonal. This
choice of S puts the condition number of B within a factor N of the
smallest possible condition number over all possible diagonal
scalings.
ARGUMENTS
 N (input) INTEGER

The order of the matrix A. N >= 0.
 A (input) COMPLEX array, dimension (LDA,N)

The NbyN symmetric matrix whose scaling
factors are to be computed. Only the diagonal elements of A
are referenced.
 LDA (input) INTEGER

The leading dimension of the array A. LDA >= max(1,N).
 S (output) REAL array, dimension (N)

If INFO = 0, S contains the scale factors for A.
 SCOND (output) REAL

If INFO = 0, S contains the ratio of the smallest S(i) to
the largest S(i). If SCOND >= 0.1 and AMAX is neither too
large nor too small, it is not worth scaling by S.
 AMAX (output) REAL

Absolute value of largest matrix element. If AMAX is very
close to overflow or very close to underflow, the matrix
should be scaled.
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = i, the ith argument had an illegal value
> 0: if INFO = i, the ith diagonal element is nonpositive.
Pages related to cheequb
 cheequb (3)
 cheev (l)  computes all eigenvalues and, optionally, eigenvectors of a complex Hermitian matrix A
 cheevd (l)  computes all eigenvalues and, optionally, eigenvectors of a complex Hermitian matrix A
 cheevr (l)  computes selected eigenvalues and, optionally, eigenvectors of a complex Hermitian matrix A
 cheevx (l)  computes selected eigenvalues and, optionally, eigenvectors of a complex Hermitian matrix A
 checon (l)  estimates the reciprocal of the condition number of a complex Hermitian matrix A using the factorization A = U*D*U**H or A = L*D*L**H computed by CHETRF
 chegs2 (l)  reduces a complex Hermitiandefinite generalized eigenproblem to standard form
 chegst (l)  reduces a complex Hermitiandefinite generalized eigenproblem to standard form