Contents
dtbcon - estimate the reciprocal of the condition number of
a triangular band matrix A, in either the 1-norm or the
infinity-norm
SUBROUTINE DTBCON(NORM, UPLO, DIAG, N, KD, A, LDA, RCOND, WORK,
WORK2, INFO)
CHARACTER * 1 NORM, UPLO, DIAG
INTEGER N, KD, LDA, INFO
INTEGER WORK2(*)
DOUBLE PRECISION RCOND
DOUBLE PRECISION A(LDA,*), WORK(*)
SUBROUTINE DTBCON_64(NORM, UPLO, DIAG, N, KD, A, LDA, RCOND, WORK,
WORK2, INFO)
CHARACTER * 1 NORM, UPLO, DIAG
INTEGER*8 N, KD, LDA, INFO
INTEGER*8 WORK2(*)
DOUBLE PRECISION RCOND
DOUBLE PRECISION A(LDA,*), WORK(*)
F95 INTERFACE
SUBROUTINE TBCON(NORM, UPLO, DIAG, [N], KD, A, [LDA], RCOND, [WORK],
[WORK2], [INFO])
CHARACTER(LEN=1) :: NORM, UPLO, DIAG
INTEGER :: N, KD, LDA, INFO
INTEGER, DIMENSION(:) :: WORK2
REAL(8) :: RCOND
REAL(8), DIMENSION(:) :: WORK
REAL(8), DIMENSION(:,:) :: A
SUBROUTINE TBCON_64(NORM, UPLO, DIAG, [N], KD, A, [LDA], RCOND,
[WORK], [WORK2], [INFO])
CHARACTER(LEN=1) :: NORM, UPLO, DIAG
INTEGER(8) :: N, KD, LDA, INFO
INTEGER(8), DIMENSION(:) :: WORK2
REAL(8) :: RCOND
REAL(8), DIMENSION(:) :: WORK
REAL(8), DIMENSION(:,:) :: A
C INTERFACE
#include <sunperf.h>
void dtbcon(char norm, char uplo, char diag, int n, int kd,
double *a, int lda, double *rcond, int *info);
void dtbcon_64(char norm, char uplo, char diag, long n, long
kd, double *a, long lda, double *rcond, long
*info);
dtbcon 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)) ).
NORM (input)
Specifies whether the 1-norm condition number or
the infinity-norm condition number is required:
= '1' or 'O': 1-norm;
= 'I': Infinity-norm.
UPLO (input)
= 'U': A is upper triangular;
= 'L': A is lower triangular.
DIAG (input)
= 'N': A is non-unit triangular;
= 'U': A is unit triangular.
N (input) The order of the matrix A. N >= 0.
KD (input)
The number of superdiagonals or subdiagonals of
the triangular band matrix A. KD >= 0.
A (input) 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 A as follows: if UPLO = 'U', A(kd+1+i-
j,j) = A(i,j) for max(1,j-kd)<=i<=j; if UPLO =
'L', A(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.
LDA (input)
The leading dimension of the array A. LDA >=
KD+1.
RCOND (output)
The reciprocal of the condition number of the
matrix A, computed as RCOND = 1/(norm(A) *
norm(inv(A))).
WORK (workspace)
dimension(3*N)
WORK2 (workspace)
dimension(N)
INFO (output)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille-
gal value