• NAME
• SYNOPSIS
• F95 INTERFACE
• C INTERFACE
• PURPOSE
• ARGUMENTS

NAME

sgecon - 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 SGECON( NORM, N, A, LDA, ANORM, RCOND, WORK, WORK2, INFO)
  CHARACTER * 1 NORM
  INTEGER N, LDA, INFO
  INTEGER WORK2(*)
  REAL ANORM, RCOND
  REAL A(LDA,*), WORK(*)

  SUBROUTINE SGECON_64( NORM, N, A, LDA, ANORM, RCOND, WORK, WORK2, 
 *      INFO)
  CHARACTER * 1 NORM
  INTEGER*8 N, LDA, INFO
  INTEGER*8 WORK2(*)
  REAL ANORM, RCOND
  REAL 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 :: ANORM, RCOND
  REAL, DIMENSION(:) :: WORK
  REAL, 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 :: ANORM, RCOND
  REAL, DIMENSION(:) :: WORK
  REAL, DIMENSION(:,:) :: A

C INTERFACE

#include <sunperf.h>

void sgecon(char norm, int n, float *a, int lda, float anorm, float *rcond, int *info);

void sgecon_64(char norm, long n, float *a, long lda, float anorm, float *rcond, long *info);

PURPOSE

sgecon 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:

   = '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 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(4*N)

• WORK2 (workspace)
  dimension(N)

• INFO (output)
  

   = 0:  successful exit

   < 0:  if INFO  = -i, the i-th argument had an illegal value