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NAME DPPTRI - 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 DPPTRF SYNOPSIS SUBROUTINE DPPTRI( UPLO, N, AP, INFO ) CHARACTER UPLO INTEGER INFO, N DOUBLE PRECISION AP( * ) PURPOSE DPPTRI 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 DPPTRF. 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. (N*(N+1)/2) AP (input/output) DOUBLE PRECISION array, dimension On entry, the triangular factor U or L from the Cholesky factorization A = U**T*U or A = L*L**T, packed columnwise as a linear array. The j-th column of U or L is stored in the array AP as fol- lows: 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 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.