dspcon (l)  Linux Manuals
dspcon: estimates the reciprocal of the condition number (in the 1norm) of a real symmetric packed matrix A using the factorization A = U*D*U**T or A = L*D*L**T computed by DSPTRF
Command to display dspcon
manual in Linux: $ man l dspcon
NAME
DSPCON  estimates the reciprocal of the condition number (in the 1norm) of a real symmetric packed matrix A using the factorization A = U*D*U**T or A = L*D*L**T computed by DSPTRF
SYNOPSIS
 SUBROUTINE DSPCON(

UPLO, N, AP, IPIV, ANORM, RCOND, WORK, IWORK,
INFO )

CHARACTER
UPLO

INTEGER
INFO, N

DOUBLE
PRECISION ANORM, RCOND

INTEGER
IPIV( * ), IWORK( * )

DOUBLE
PRECISION AP( * ), WORK( * )
PURPOSE
DSPCON estimates the reciprocal of the condition number (in the
1norm) of a real symmetric packed matrix A using the factorization
A = U*D*U**T or A = L*D*L**T computed by DSPTRF.
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.
 AP (input) DOUBLE PRECISION array, dimension (N*(N+1)/2)

The block diagonal matrix D and the multipliers used to
obtain the factor U or L as computed by DSPTRF, stored as a
packed triangular matrix.
 IPIV (input) INTEGER array, dimension (N)

Details of the interchanges and the block structure of D
as determined by DSPTRF.
 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
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