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.

       AP        (input/output)   DOUBLE   PRECISION   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  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 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 com­
               puted.


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