Contents
dgecon - estimate the reciprocal of the condition number of
a general real matrix A, in either the 1-norm or the
infinity-norm, using the LU factorization computed by DGETRF
SUBROUTINE DGECON(NORM, N, A, LDA, ANORM, RCOND, WORK, WORK2, INFO)
CHARACTER * 1 NORM
INTEGER N, LDA, INFO
INTEGER WORK2(*)
DOUBLE PRECISION ANORM, RCOND
DOUBLE PRECISION A(LDA,*), WORK(*)
SUBROUTINE DGECON_64(NORM, N, A, LDA, ANORM, RCOND, WORK, WORK2,
INFO)
CHARACTER * 1 NORM
INTEGER*8 N, LDA, INFO
INTEGER*8 WORK2(*)
DOUBLE PRECISION ANORM, RCOND
DOUBLE PRECISION A(LDA,*), WORK(*)
F95 INTERFACE
SUBROUTINE GECON(NORM, [N], A, [LDA], ANORM, RCOND, [WORK], [WORK2],
[INFO])
CHARACTER(LEN=1) :: NORM
INTEGER :: N, LDA, INFO
INTEGER, DIMENSION(:) :: WORK2
REAL(8) :: ANORM, RCOND
REAL(8), DIMENSION(:) :: WORK
REAL(8), DIMENSION(:,:) :: A
SUBROUTINE GECON_64(NORM, [N], A, [LDA], ANORM, RCOND, [WORK], [WORK2],
[INFO])
CHARACTER(LEN=1) :: NORM
INTEGER(8) :: N, LDA, INFO
INTEGER(8), DIMENSION(:) :: WORK2
REAL(8) :: ANORM, RCOND
REAL(8), DIMENSION(:) :: WORK
REAL(8), DIMENSION(:,:) :: A
C INTERFACE
#include <sunperf.h>
void dgecon(char norm, int n, double *a, int lda, double
anorm, double *rcond, int *info);
void dgecon_64(char norm, long n, double *a, long lda, dou-
ble anorm, double *rcond, long *info);
dgecon estimates the reciprocal of the condition number of a
general real matrix A, in either the 1-norm or the
infinity-norm, using the LU factorization computed by
DGETRF.
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.
A (input) The factors L and U from the factorization A =
P*L*U as computed by DGETRF.
LDA (input)
The leading dimension of the array A. LDA >=
max(1,N).
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(4*N)
WORK2 (workspace)
dimension(N)
INFO (output)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille-
gal value