dgbcon()

subroutine dgbcon	(	character	norm,
		integer	n,
		integer	kl,
		integer	ku,
		double precision, dimension( ldab, * )	ab,
		integer	ldab,
		integer, dimension( * )	ipiv,
		double precision	anorm,
		double precision	rcond,
		double precision, dimension( * )	work,
		integer, dimension( * )	iwork,
		integer	info )

DGBCON

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Purpose:

!>
!> DGBCON estimates the reciprocal of the condition number of a real
!> general band matrix A, in either the 1-norm or the infinity-norm,
!> using the LU factorization computed by DGBTRF.
!>
!> 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]	KL	!> KL is INTEGER !> The number of subdiagonals within the band of A. KL >= 0. !>
[in]	KU	!> KU is INTEGER !> The number of superdiagonals within the band of A. KU >= 0. !>
[in]	AB	!> AB is DOUBLE PRECISION array, dimension (LDAB,N) !> Details of the LU factorization of the band matrix A, as !> computed by DGBTRF. U is stored as an upper triangular band !> matrix with KL+KU superdiagonals in rows 1 to KL+KU+1, and !> the multipliers used during the factorization are stored in !> rows KL+KU+2 to 2*KL+KU+1. !>
[in]	LDAB	!> LDAB is INTEGER !> The leading dimension of the array AB. LDAB >= 2*KL+KU+1. !>
[in]	IPIV	!> IPIV is INTEGER array, dimension (N) !> The pivot indices; for 1 <= i <= N, row i of the matrix was !> interchanged with row IPIV(i). !>
[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 DOUBLE PRECISION array, dimension (3*N) !>
[out]	IWORK	!> IWORK is INTEGER array, dimension (N) !>
[out]	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.