
ZTRCON(l) ) ZTRCON(l)
NAME
ZTRCON  estimate the reciprocal of the condition number of a triangular matrix A, in
either the 1norm or the infinitynorm
SYNOPSIS
SUBROUTINE ZTRCON( NORM, UPLO, DIAG, N, A, LDA, RCOND, WORK, RWORK, INFO )
CHARACTER DIAG, NORM, UPLO
INTEGER INFO, LDA, N
DOUBLE PRECISION RCOND
DOUBLE PRECISION RWORK( * )
COMPLEX*16 A( LDA, * ), WORK( * )
PURPOSE
ZTRCON 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)) ).
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.
UPLO (input) CHARACTER*1
= 'U': A is upper triangular;
= 'L': A is lower triangular.
DIAG (input) CHARACTER*1
= 'N': A is nonunit triangular;
= 'U': A is unit triangular.
N (input) INTEGER
The order of the matrix A. N >= 0.
A (input) COMPLEX*16 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 trian
gular part of A is not referenced. If UPLO = 'L', the leading NbyN lower trian
gular 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 ele
ments of A are also not referenced and are assumed to be 1.
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(1,N).
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) COMPLEX*16 array, dimension (2*N)
RWORK (workspace) DOUBLE PRECISION 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 ZTRCON(l) 
