Contents
spptri - compute the inverse of a real symmetric positive
definite matrix A using the Cholesky factorization A =
U**T*U or A = L*L**T computed by SPPTRF
SUBROUTINE SPPTRI(UPLO, N, A, INFO)
CHARACTER * 1 UPLO
INTEGER N, INFO
REAL A(*)
SUBROUTINE SPPTRI_64(UPLO, N, A, INFO)
CHARACTER * 1 UPLO
INTEGER*8 N, INFO
REAL A(*)
F95 INTERFACE
SUBROUTINE PPTRI(UPLO, [N], A, [INFO])
CHARACTER(LEN=1) :: UPLO
INTEGER :: N, INFO
REAL, DIMENSION(:) :: A
SUBROUTINE PPTRI_64(UPLO, [N], A, [INFO])
CHARACTER(LEN=1) :: UPLO
INTEGER(8) :: N, INFO
REAL, DIMENSION(:) :: A
C INTERFACE
#include <sunperf.h>
void spptri(char uplo, int n, float *a, int *info);
void spptri_64(char uplo, long n, float *a, long *info);
spptri computes the inverse of a real symmetric positive
definite matrix A using the Cholesky factorization A =
U**T*U or A = L*L**T computed by SPPTRF.
UPLO (input)
= 'U': Upper triangular factor is stored in A;
= 'L': Lower triangular factor is stored in A.
N (input) The order of the matrix A. N >= 0.
A (input/output) REAL array, dimension (N*(N+1)/2)
On entry, the triangular factor U or L from the
Cholesky factorization A = U**T*U or A = L*L**T,
packed columnwise as a linear array. The j-th
column of U or L is stored in the array A as fol-
lows: if UPLO = 'U', A(i + (j-1)*j/2) = U(i,j)
for 1<=i<=j; if UPLO = 'L', A(i + (j-1)*(2n-j)/2)
= L(i,j) for j<=i<=n.
On exit, the upper or lower triangle of the (sym-
metric) inverse of A, overwriting the input factor
U or L.
INFO (output)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an ille-
gal value
> 0: if INFO = i, the (i,i) element of the factor
U or L is zero, and the inverse could not be com-
puted.