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# ctrcon.f

ctrcon.f −

## SYNOPSIS

Functions/Subroutines

subroutine ctrcon (NORM, UPLO, DIAG, N, A, LDA, RCOND, WORK, RWORK, INFO)
CTRCON

## Function/Subroutine Documentation

subroutine ctrcon (characterNORM, characterUPLO, characterDIAG, integerN, complex, dimension( lda, * )A, integerLDA, realRCOND, complex, dimension( * )WORK, real, dimension( * )RWORK, integerINFO)
CTRCON

Purpose:

CTRCON estimates the reciprocal of the condition number of a
triangular matrix A, in either the 1-norm or the infinity-norm.

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 1-norm condition number or the
infinity-norm condition number is required:
= ’1’ or ’O’: 1-norm;
= ’I’: Infinity-norm.

UPLO

UPLO is CHARACTER*1
= ’U’: A is upper triangular;
= ’L’: A is lower triangular.

DIAG

DIAG is CHARACTER*1
= ’N’: A is non-unit triangular;
= ’U’: A is unit triangular.

N

N is INTEGER
The order of the matrix A. N >= 0.

A

A is COMPLEX array, dimension (LDA,N)
The triangular matrix A. If UPLO = ’U’, the leading N-by-N
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 N-by-N 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.

LDA

LDA is INTEGER
The leading dimension of the array A. LDA >= max(1,N).

RCOND

RCOND is REAL
The reciprocal of the condition number of the matrix A,
computed as RCOND = 1/(norm(A) * norm(inv(A))).

WORK

WORK is COMPLEX array, dimension (2*N)

RWORK

RWORK is REAL array, dimension (N)

INFO

INFO is INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th 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 ctrcon.f.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

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