dgecon

NAME

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 SGETRF

SYNOPSIS

  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, double anorm, double *rcond, long *info);

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 SGETRF.

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): Specifies whether the 1-norm condition number or the infinity-norm condition number is required:
* 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 SGETRF.
* 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(2*N)
* WORK2 (workspace)
* INFO (output)