zgecon()

subroutine zgecon	(	character	norm,
		integer	n,
		complex*16, dimension( lda, * )	a,
		integer	lda,
		double precision	anorm,
		double precision	rcond,
		complex*16, dimension( * )	work,
		double precision, dimension( * )	rwork,
		integer	info
	)

ZGECON

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Purpose:

 ZGECON estimates the reciprocal of the condition number of a general
 complex matrix A, in either the 1-norm or the infinity-norm, using
 the LU factorization computed by ZGETRF.

 An estimate is obtained for norm(inv(A)), and the reciprocal of the
 condition number is computed as
    RCOND = 1 / ( norm(A) * norm(inv(A)) ).

Parameters

[in]	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.
[in]	N	N is INTEGER The order of the matrix A. N >= 0.
[in]	A	A is COMPLEX*16 array, dimension (LDA,N) The factors L and U from the factorization A = P*L*U as computed by ZGETRF.
[in]	LDA	LDA is INTEGER The leading dimension of the array A. LDA >= max(1,N).
[in]	ANORM	ANORM is DOUBLE PRECISION If NORM = '1' or 'O', the 1-norm of the original matrix A. If NORM = 'I', the infinity-norm of the original matrix A.
[out]	RCOND	RCOND is DOUBLE PRECISION The reciprocal of the condition number of the matrix A, computed as RCOND = 1/(norm(A) * norm(inv(A))).
[out]	WORK	WORK is COMPLEX*16 array, dimension (2*N)
[out]	RWORK	RWORK is DOUBLE PRECISION array, dimension (2*N)
[out]	INFO	INFO is INTEGER = 0: successful exit < 0: if INFO = -i, the i-th argument had an illegal value. NaNs are illegal values for ANORM, and they propagate to the output parameter RCOND. Infinity is illegal for ANORM, and it propagates to the output parameter RCOND as 0. = 1: if RCOND = NaN, or RCOND = Inf, or the computed norm of the inverse of A is 0. In the latter, RCOND = 0 is returned.

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.