---
name: "spotri"
section: "3lapack"
platform: "linux"
package: "liblapack-doc"
version: "3.2.1-8"
release: "Debian 6.0 (Squeeze)"
platforms: ["linux"]
url: "https://new.carta.tech/spotri/3lapack"
---

# spotri(3lapack)

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

## NAME

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

## 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, 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.