Contents
ssptri - 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
SUBROUTINE SSPTRI(UPLO, N, AP, IPIVOT, WORK, INFO)
CHARACTER * 1 UPLO
INTEGER N, INFO
INTEGER IPIVOT(*)
REAL AP(*), WORK(*)
SUBROUTINE SSPTRI_64(UPLO, N, AP, IPIVOT, WORK, INFO)
CHARACTER * 1 UPLO
INTEGER*8 N, INFO
INTEGER*8 IPIVOT(*)
REAL AP(*), WORK(*)
F95 INTERFACE
SUBROUTINE SPTRI(UPLO, [N], AP, IPIVOT, [WORK], [INFO])
CHARACTER(LEN=1) :: UPLO
INTEGER :: N, INFO
INTEGER, DIMENSION(:) :: IPIVOT
REAL, DIMENSION(:) :: AP, WORK
SUBROUTINE SPTRI_64(UPLO, [N], AP, IPIVOT, [WORK], [INFO])
CHARACTER(LEN=1) :: UPLO
INTEGER(8) :: N, INFO
INTEGER(8), DIMENSION(:) :: IPIVOT
REAL, DIMENSION(:) :: AP, WORK
C INTERFACE
#include <sunperf.h>
void ssptri(char uplo, int n, float *a, int *ipivot, int
*info);
void ssptri_64(char uplo, long n, float *a, long *ipivot,
long *info);
ssptri 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.
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.
AP (input/output)
Real array, dimension (N*(N+1)/2) 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 AP as follows: if UPLO = 'U', AP(i + (j-
1)*j/2) = inv(A)(i,j) for 1<=i<=j; if UPLO = 'L',
AP(i + (j-1)*(2n-j)/2) = inv(A)(i,j) for j<=i<=n.
IPIVOT (input)
Integer array, dimension (N) Details of the inter-
changes and the block structure of D as determined
by SSPTRF.
WORK (workspace)
Real array, dimension(N)
INFO (output)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille-
gal value
> 0: if INFO = i, D(i,i) = 0; the matrix is singu-
lar and its inverse could not be computed.