
SGECON(l) ) SGECON(l)
NAME
SGECON  estimate the reciprocal of the condition number of a general real matrix A, in
either the 1norm or the infinitynorm, using the LU factorization computed by SGETRF
SYNOPSIS
SUBROUTINE SGECON( NORM, N, A, LDA, ANORM, RCOND, WORK, IWORK, INFO )
CHARACTER NORM
INTEGER INFO, LDA, N
REAL ANORM, RCOND
INTEGER IWORK( * )
REAL A( LDA, * ), WORK( * )
PURPOSE
SGECON estimates the reciprocal of the condition number of a general real matrix A, in
either the 1norm or the infinitynorm, using the LU factorization computed by SGETRF. An
estimate is obtained for norm(inv(A)), and the reciprocal of the condition number is com
puted as
RCOND = 1 / ( norm(A) * norm(inv(A)) ).
ARGUMENTS
NORM (input) CHARACTER*1
Specifies whether the 1norm condition number or the infinitynorm condition num
ber is required:
= '1' or 'O': 1norm;
= 'I': Infinitynorm.
N (input) INTEGER
The order of the matrix A. N >= 0.
A (input) REAL array, dimension (LDA,N)
The factors L and U from the factorization A = P*L*U as computed by SGETRF.
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(1,N).
ANORM (input) REAL
If NORM = '1' or 'O', the 1norm of the original matrix A. If NORM = 'I', the
infinitynorm of the original matrix A.
RCOND (output) REAL
The reciprocal of the condition number of the matrix A, computed as RCOND =
1/(norm(A) * norm(inv(A))).
WORK (workspace) REAL array, dimension (4*N)
IWORK (workspace) INTEGER array, dimension (N)
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = i, the ith argument had an illegal value
LAPACK version 3.0 15 June 2000 SGECON(l) 
