dsptri

NAME

dsptri - compute the inverse of a real symmetric indefinite matrix A in packed storage using the factorization A = U*D*U**T or A = L*D*L**T computed by SSPTRF

SYNOPSIS 

  SUBROUTINE DSPTRI( UPLO, N, A, IPIVOT, WORK, INFO)
  CHARACTER * 1 UPLO
  INTEGER N, INFO
  INTEGER IPIVOT(*)
  DOUBLE PRECISION A(*), WORK(*)
 
  SUBROUTINE DSPTRI_64( UPLO, N, A, IPIVOT, WORK, INFO)
  CHARACTER * 1 UPLO
  INTEGER*8 N, INFO
  INTEGER*8 IPIVOT(*)
  DOUBLE PRECISION A(*), WORK(*)

F95 INTERFACE 

  SUBROUTINE SPTRI( UPLO, N, A, IPIVOT, [WORK], [INFO])
  CHARACTER(LEN=1) :: UPLO
  INTEGER :: N, INFO
  INTEGER, DIMENSION(:) :: IPIVOT
  REAL(8), DIMENSION(:) :: A, WORK
 
  SUBROUTINE SPTRI_64( UPLO, N, A, IPIVOT, [WORK], [INFO])
  CHARACTER(LEN=1) :: UPLO
  INTEGER(8) :: N, INFO
  INTEGER(8), DIMENSION(:) :: IPIVOT
  REAL(8), DIMENSION(:) :: A, WORK

C INTERFACE

#include <sunperf.h>

void dsptri(char uplo, int n, double *a, int *ipivot, int *info);

void dsptri_64(char uplo, long n, double *a, long *ipivot, long *info);

PURPOSE

dsptri computes the inverse of a real symmetric indefinite matrix A in packed storage using the factorization A = U*D*U**T or A = L*D*L**T computed by SSPTRF.

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/output)
On entry, 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.

On exit, if INFO = 0, the (symmetric) inverse of the original matrix, stored as a packed triangular matrix. The j-th column of inv(A) is stored in the array A as follows: if UPLO = 'U', A(i + (j-1)*j/2) = inv(A)(i,j) for 1<=i<=j; if UPLO = 'L', A(i + (j-1)*(2n-j)/2) = inv(A)(i,j) for j<=i<=n.

* IPIVOT (input)
Details of the interchanges and the block structure of D as determined by SSPTRF.

* WORK (workspace)
dimension(N)

* INFO (output)