ctbcon-f(3)

ctbcon.f –

Synopsis

Functions/Subroutines

subroutine ctbcon (NORM, UPLO, DIAG, N, KD, AB, LDAB, RCOND, WORK, RWORK, INFO)
CTBCON

Function/Subroutine Documentation

subroutine ctbcon (characterNORM, characterUPLO, characterDIAG, integerN, integerKD, complex, dimension( ldab, * )AB, integerLDAB, realRCOND, complex, dimension( * )WORK, real, dimension( * )RWORK, integerINFO)

CTBCON

Purpose:

 CTBCON estimates the reciprocal of the condition number of a
 triangular band 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 is INTEGER
 The order of the matrix A. N >= 0.

 KD is INTEGER
 The number of superdiagonals or subdiagonals of the
 triangular band matrix A. KD >= 0.

 AB is COMPLEX array, dimension (LDAB,N)
 The upper or lower triangular band matrix A, stored in the
 first kd+1 rows of the array. The j-th column of A is stored
 in the j-th column of the array AB as follows:
 if UPLO = 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j;
 if UPLO = 'L', AB(1+i-j,j) = A(i,j) for j<=i<=min(n,j+kd).
 If DIAG = 'U', the diagonal elements of A are not referenced
 and are assumed to be 1.

LDAB

 LDAB is INTEGER
 The leading dimension of the array AB. LDAB >= KD+1.

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 143 of file ctbcon.f.

Author

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