dgecon (l)  Linux Man Pages
dgecon: 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 DGETRF
NAME
DGECON  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 DGETRFSYNOPSIS
 SUBROUTINE DGECON(
 NORM, N, A, LDA, ANORM, RCOND, WORK, IWORK, INFO )
 CHARACTER NORM
 INTEGER INFO, LDA, N
 DOUBLE PRECISION ANORM, RCOND
 INTEGER IWORK( * )
 DOUBLE PRECISION A( LDA, * ), WORK( * )
PURPOSE
DGECON 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 DGETRF. An estimate is obtained for norm(inv(A)), and the reciprocal of the condition number is computed asRCOND
ARGUMENTS
 NORM (input) CHARACTER*1

Specifies whether the 1norm condition number or the
infinitynorm condition number is required:
= aq1aq or aqOaq: 1norm;
= aqIaq: Infinitynorm.  N (input) INTEGER
 The order of the matrix A. N >= 0.
 A (input) DOUBLE PRECISION array, dimension (LDA,N)
 The factors L and U from the factorization A = P*L*U as computed by DGETRF.
 LDA (input) INTEGER
 The leading dimension of the array A. LDA >= max(1,N).
 ANORM (input) DOUBLE PRECISION
 If NORM = aq1aq or aqOaq, the 1norm of the original matrix A. If NORM = aqIaq, the infinitynorm of the original matrix A.
 RCOND (output) DOUBLE PRECISION
 The reciprocal of the condition number of the matrix A, computed as RCOND = 1/(norm(A) * norm(inv(A))).
 WORK (workspace) DOUBLE PRECISION 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