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dpptri

 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.