DGECON
Modified to call DLACN2 in place of DLACON, 5 Feb 03, SJH.
Purpose
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)) ).
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)) ).
Arguments
| NORM |
(input) 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 |
(input) INTEGER
The order of the matrix A. N >= 0.
|
| A |
(input) DOUBLE PRECISION array, dimension (LDA,N)
The factors L and U from the factorization A = P*L*U
as computed by DGETRF. |
| LDA |
(input) INTEGER
The leading dimension of the array A. LDA >= max(1,N).
|
| ANORM |
(input) 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 |
(output) DOUBLE PRECISION
The reciprocal of the condition number of the matrix A,
computed as RCOND = 1/(norm(A) * norm(inv(A))). |
| WORK |
(workspace) DOUBLE PRECISION array, dimension (4*N)
|
| IWORK |
(workspace) INTEGER array, dimension (N)
|
| INFO |
(output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value |