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

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. = 'U': Upper triangular, form is A = U*D*U**T;

   = 'L':  Lower triangular, form is A  = L*D*L**T.

• 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)
  

   = 0: successful exit

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

   > 0: if INFO  = i, D(i,i)  = 0; the matrix is singular and its
  inverse could not be computed.