Contents
dgbcon - estimate the reciprocal of the condition number of
a real general band matrix A, in either the 1-norm or the
infinity-norm,
SUBROUTINE DGBCON(NORM, N, NSUB, NSUPER, A, LDA, IPIVOT, ANORM,
RCOND, WORK, WORK2, INFO)
CHARACTER * 1 NORM
INTEGER N, NSUB, NSUPER, LDA, INFO
INTEGER IPIVOT(*), WORK2(*)
DOUBLE PRECISION ANORM, RCOND
DOUBLE PRECISION A(LDA,*), WORK(*)
SUBROUTINE DGBCON_64(NORM, N, NSUB, NSUPER, A, LDA, IPIVOT, ANORM,
RCOND, WORK, WORK2, INFO)
CHARACTER * 1 NORM
INTEGER*8 N, NSUB, NSUPER, LDA, INFO
INTEGER*8 IPIVOT(*), WORK2(*)
DOUBLE PRECISION ANORM, RCOND
DOUBLE PRECISION A(LDA,*), WORK(*)
F95 INTERFACE
SUBROUTINE GBCON(NORM, [N], NSUB, NSUPER, A, [LDA], IPIVOT, ANORM,
RCOND, [WORK], [WORK2], [INFO])
CHARACTER(LEN=1) :: NORM
INTEGER :: N, NSUB, NSUPER, LDA, INFO
INTEGER, DIMENSION(:) :: IPIVOT, WORK2
REAL(8) :: ANORM, RCOND
REAL(8), DIMENSION(:) :: WORK
REAL(8), DIMENSION(:,:) :: A
SUBROUTINE GBCON_64(NORM, [N], NSUB, NSUPER, A, [LDA], IPIVOT, ANORM,
RCOND, [WORK], [WORK2], [INFO])
CHARACTER(LEN=1) :: NORM
INTEGER(8) :: N, NSUB, NSUPER, LDA, INFO
INTEGER(8), DIMENSION(:) :: IPIVOT, WORK2
REAL(8) :: ANORM, RCOND
REAL(8), DIMENSION(:) :: WORK
REAL(8), DIMENSION(:,:) :: A
C INTERFACE
#include <sunperf.h>
void dgbcon(char norm, int n, int nsub, int nsuper, double
*a, int lda, int *ipivot, double anorm, double
*rcond, int *info);
void dgbcon_64(char norm, long n, long nsub, long nsuper,
double *a, long lda, long *ipivot, double anorm,
double *rcond, long *info);
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
SGBTRF.
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)) ).
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.
N (input) The order of the matrix A. N >= 0.
NSUB (input)
The number of subdiagonals within the band of A.
NSUB >= 0.
NSUPER (input)
The number of superdiagonals within the band of A.
NSUPER >= 0.
A (input) Details of the LU factorization of the band matrix
A, as computed by SGBTRF. U is stored as an upper
triangular band matrix with NSUB+NSUPER superdiag-
onals in rows 1 to NSUB+NSUPER+1, and the multi-
pliers used during the factorization are stored in
rows NSUB+NSUPER+2 to 2*NSUB+NSUPER+1.
LDA (input)
The leading dimension of the array A. LDA >=
2*NSUB+NSUPER+1.
IPIVOT (input)
The pivot indices; for 1 <= i <= N, row i of the
matrix was interchanged with row IPIVOT(i).
ANORM (input)
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 (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