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# spotri

```
NAME
SPOTRI - 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 SPOTRF

SYNOPSIS
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, overwrit-
ing 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.
```