spotri3lapack
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 spotrf
Usage
- SUBROUTINE SPOTRI(
-
UPLO, N, A, LDA, INFO )
- CHARACTER
-
UPLO
- INTEGER
-
INFO, LDA, N
- REAL
-
A( LDA, * )
Purpose
SPOTRI 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 SPOTRF.
Arguments
- UPLO (input) CHARACTER*1
-
= 'U': Upper triangle of A is stored;
= 'L': Lower triangle of A is stored.
- N (input) INTEGER
-
The order of the matrix A. N >= 0.
- A (input/output) REAL array, dimension (LDA,N)
-
On entry, the triangular factor U or L from the Cholesky factorization A = U**T*U or A = L*L**T, as computed by SPOTRF. On exit, the upper or lower triangle of the (symmetric) inverse of A, overwriting the input factor U or L.
- LDA (input) INTEGER
-
The leading dimension of the array A. LDA >= max(1,N).
- INFO (output) INTEGER
-
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, the (i,i) element of the factor U or L is zero, and the inverse could not be computed.