SPOTRI (3lapack)

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,
          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.