dsycon (l)  Linux Man Pages
dsycon: estimates the reciprocal of the condition number (in the 1norm) of a real symmetric matrix A using the factorization A = U*D*U**T or A = L*D*L**T computed by DSYTRF
Command to display dsycon
manual in Linux: $ man l dsycon
NAME
DSYCON  estimates the reciprocal of the condition number (in the 1norm) of a real symmetric matrix A using the factorization A = U*D*U**T or A = L*D*L**T computed by DSYTRF
SYNOPSIS
 SUBROUTINE DSYCON(

UPLO, N, A, LDA, IPIV, ANORM, RCOND, WORK,
IWORK, INFO )

CHARACTER
UPLO

INTEGER
INFO, LDA, N

DOUBLE
PRECISION ANORM, RCOND

INTEGER
IPIV( * ), IWORK( * )

DOUBLE
PRECISION A( LDA, * ), WORK( * )
PURPOSE
DSYCON estimates the reciprocal of the condition number (in the
1norm) of a real symmetric matrix A using the factorization
A = U*D*U**T or A = L*D*L**T computed by DSYTRF.
An estimate is obtained for norm(inv(A)), and the reciprocal of the
condition number is computed as RCOND = 1 / (ANORM * norm(inv(A))).
ARGUMENTS
 UPLO (input) CHARACTER*1

Specifies whether the details of the factorization are stored
as an upper or lower triangular matrix.
= aqUaq: Upper triangular, form is A = U*D*U**T;
= aqLaq: Lower triangular, form is A = L*D*L**T.
 N (input) INTEGER

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

The block diagonal matrix D and the multipliers used to
obtain the factor U or L as computed by DSYTRF.
 LDA (input) INTEGER

The leading dimension of the array A. LDA >= max(1,N).
 IPIV (input) INTEGER array, dimension (N)

Details of the interchanges and the block structure of D
as determined by DSYTRF.
 ANORM (input) DOUBLE PRECISION

The 1norm of the original matrix A.
 RCOND (output) DOUBLE PRECISION

The reciprocal of the condition number of the matrix A,
computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is an
estimate of the 1norm of inv(A) computed in this routine.
 WORK (workspace) DOUBLE PRECISION array, dimension (2*N)

 IWORK (workspace) INTEGER array, dimension (N)

 INFO (output) INTEGER

= 0: successful exit
< 0: if INFO = i, the ith argument had an illegal value
Pages related to dsycon
 dsycon (3)
 dsyequb (l)  computes row and column scalings intended to equilibrate a symmetric matrix A and reduce its condition number (with respect to the twonorm)
 dsyev (l)  computes all eigenvalues and, optionally, eigenvectors of a real symmetric matrix A
 dsyevd (l)  computes all eigenvalues and, optionally, eigenvectors of a real symmetric matrix A
 dsyevr (l)  computes selected eigenvalues and, optionally, eigenvectors of a real symmetric matrix A
 dsyevx (l)  computes selected eigenvalues and, optionally, eigenvectors of a real symmetric matrix A
 dsygs2 (l)  reduces a real symmetricdefinite generalized eigenproblem to standard form
 dsygst (l)  reduces a real symmetricdefinite generalized eigenproblem to standard form