dspcon

NAME

dspcon - estimate the reciprocal of the condition number (in the 1-norm) of a real symmetric packed matrix A using the factorization A = U*D*U**T or A = L*D*L**T computed by SSPTRF

SYNOPSIS

  SUBROUTINE DSPCON( UPLO, N, A, IPIVOT, ANORM, RCOND, WORK, IWORK2, 
 *      INFO)
  CHARACTER * 1 UPLO
  INTEGER N, INFO
  INTEGER IPIVOT(*), IWORK2(*)
  DOUBLE PRECISION ANORM, RCOND
  DOUBLE PRECISION A(*), WORK(*)
 
  SUBROUTINE DSPCON_64( UPLO, N, A, IPIVOT, ANORM, RCOND, WORK, 
 *      IWORK2, INFO)
  CHARACTER * 1 UPLO
  INTEGER*8 N, INFO
  INTEGER*8 IPIVOT(*), IWORK2(*)
  DOUBLE PRECISION ANORM, RCOND
  DOUBLE PRECISION A(*), WORK(*)

F95 INTERFACE

  SUBROUTINE SPCON( UPLO, [N], A, IPIVOT, ANORM, RCOND, [WORK], 
 *       [IWORK2], [INFO])
  CHARACTER(LEN=1) :: UPLO
  INTEGER :: N, INFO
  INTEGER, DIMENSION(:) :: IPIVOT, IWORK2
  REAL(8) :: ANORM, RCOND
  REAL(8), DIMENSION(:) :: A, WORK
 
  SUBROUTINE SPCON_64( UPLO, [N], A, IPIVOT, ANORM, RCOND, [WORK], 
 *       [IWORK2], [INFO])
  CHARACTER(LEN=1) :: UPLO
  INTEGER(8) :: N, INFO
  INTEGER(8), DIMENSION(:) :: IPIVOT, IWORK2
  REAL(8) :: ANORM, RCOND
  REAL(8), DIMENSION(:) :: A, WORK

C INTERFACE

#include <sunperf.h>

void dspcon(char uplo, int n, double *a, int *ipivot, double anorm, double *rcond, int *info);

void dspcon_64(char uplo, long n, double *a, long *ipivot, double anorm, double *rcond, long *info);

PURPOSE

dspcon estimates the reciprocal of the condition number (in the 1-norm) of a real symmetric packed matrix A using the factorization A = U*D*U**T or A = L*D*L**T computed by SSPTRF.

An estimate is obtained for norm(inv(A)), and the reciprocal of the condition number is computed as RCOND = 1 / (ANORM * norm(inv(A))).

ARGUMENTS

* UPLO (input): Specifies whether the details of the factorization are stored as an upper or lower triangular matrix.
* N (input): The order of the matrix A. N >= 0.
* A (input): The block diagonal matrix D and the multipliers used to obtain the factor U or L as computed by SSPTRF, stored as a packed triangular matrix.
* IPIVOT (input): Details of the interchanges and the block structure of D as determined by SSPTRF.
* ANORM (input): The 1-norm of the original matrix A.
* RCOND (output): The reciprocal of the condition number of the matrix A, computed as RCOND = 1/(ANORM * AINVNM), where AINVNM is an estimate of the 1-norm of inv(A) computed in this routine.
* WORK (workspace): dimension(2*N)
* IWORK2 (workspace)
* INFO (output)