spptri(3)

NAME

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

SYNOPSIS

SUBROUTINE SPPTRI( UPLO, N, AP, INFO )
    CHARACTER      UPLO
    INTEGER        INFO, N
    REAL           AP( * )

PURPOSE

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.

ARGUMENTS

UPLO (input) CHARACTER*1

= 'U': Upper triangular factor is stored in AP;
= 'L': Lower triangular factor is stored in AP.

N (input) INTEGER

The order of the matrix A. N >= 0.

AP (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 column

wise as a linear array. The j-th column of U or L is stored in

the array AP as follows: if UPLO = 'U', AP(i + (j-1)*j/2) =

U(i,j) for 1<=i<=j; if UPLO = 'L', AP(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) INTEGER

= 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 computed.

LAPACK version 3.0 15 June 2000

SPPTRI(3)