DTRCON (3)  Linux Man Pages
NAME
dtrcon.f 
SYNOPSIS
Functions/Subroutines
subroutine dtrcon (NORM, UPLO, DIAG, N, A, LDA, RCOND, WORK, IWORK, INFO)
DTRCON
Function/Subroutine Documentation
subroutine dtrcon (characterNORM, characterUPLO, characterDIAG, integerN, double precision, dimension( lda, * )A, integerLDA, double precisionRCOND, double precision, dimension( * )WORK, integer, dimension( * )IWORK, integerINFO)
DTRCON
Purpose:

DTRCON estimates the reciprocal of the condition number of a triangular matrix A, in either the 1norm or the infinitynorm. The norm of A is computed and an estimate is obtained for norm(inv(A)), then the reciprocal of the condition number is computed as RCOND = 1 / ( norm(A) * norm(inv(A)) ).
Parameters:

NORM
NORM is CHARACTER*1 Specifies whether the 1norm condition number or the infinitynorm condition number is required: = '1' or 'O': 1norm; = 'I': Infinitynorm.
UPLOUPLO is CHARACTER*1 = 'U': A is upper triangular; = 'L': A is lower triangular.
DIAGDIAG is CHARACTER*1 = 'N': A is nonunit triangular; = 'U': A is unit triangular.
NN is INTEGER The order of the matrix A. N >= 0.
AA is DOUBLE PRECISION array, dimension (LDA,N) The triangular matrix A. If UPLO = 'U', the leading NbyN upper triangular part of the array A contains the upper triangular matrix, and the strictly lower triangular part of A is not referenced. If UPLO = 'L', the leading NbyN lower triangular part of the array A contains the lower triangular matrix, and the strictly upper triangular part of A is not referenced. If DIAG = 'U', the diagonal elements of A are also not referenced and are assumed to be 1.
LDALDA is INTEGER The leading dimension of the array A. LDA >= max(1,N).
RCONDRCOND is DOUBLE PRECISION The reciprocal of the condition number of the matrix A, computed as RCOND = 1/(norm(A) * norm(inv(A))).
WORKWORK is DOUBLE PRECISION array, dimension (3*N)
IWORKIWORK is INTEGER array, dimension (N)
INFOINFO is INTEGER = 0: successful exit < 0: if INFO = i, the ith argument had an illegal value
Author:

Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
 November 2011
Definition at line 137 of file dtrcon.f.
Author
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