dgbcon-f(3)

dgbcon.f –

Synopsis

Functions/Subroutines

subroutine dgbcon (NORM, N, KL, KU, AB, LDAB, IPIV, ANORM, RCOND, WORK, IWORK, INFO)
DGBCON

Function/Subroutine Documentation

subroutine dgbcon (characterNORM, integerN, integerKL, integerKU, double precision, dimension( ldab, * )AB, integerLDAB, integer, dimension( * )IPIV, double precisionANORM, double precisionRCOND, double precision, dimension( * )WORK, integer, dimension( * )IWORK, integerINFO)

DGBCON

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:

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.

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

 KL is INTEGER
 The number of subdiagonals within the band of A. KL >= 0.

 KU is INTEGER
 The number of superdiagonals within the band of A. KU >= 0.

 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.

LDAB

 LDAB is INTEGER
 The leading dimension of the array AB. LDAB >= 2*KL+KU+1.

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).

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.

RCOND

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

WORK

 WORK is DOUBLE PRECISION array, dimension (3*N)

IWORK

 IWORK is INTEGER 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 146 of file dgbcon.f.

Author

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