CHPTRI - compute the inverse of a complex Hermitian indef­
       inite matrix A in packed storage using the factorization A
       = U*D*U**H or A = L*D*L**H computed by CHPTRF


SYNOPSIS

       SUBROUTINE CHPTRI( UPLO, N, AP, IPIV, WORK, INFO )

           CHARACTER      UPLO

           INTEGER        INFO, N

           INTEGER        IPIV( * )

           COMPLEX        AP( * ), WORK( * )


PURPOSE

       CHPTRI computes the inverse of a complex Hermitian indefi­
       nite matrix A in packed storage using the factorization  A
       = U*D*U**H or A = L*D*L**H computed by CHPTRF.


ARGUMENTS

       UPLO    (input) CHARACTER*1
               Specifies whether the details of the factorization
               are stored as an upper or lower triangular matrix.
               = 'U':  Upper triangular, form is A = U*D*U**H;
               = 'L':  Lower triangular, form is A = L*D*L**H.

       N       (input) INTEGER
               The order of the matrix A.  N >= 0.

       AP      (input/output) COMPLEX array, dimension
               (N*(N+1)/2)
               On entry, the block diagonal matrix D and the mul­
               tipliers  used to obtain the factor U or L as com­
               puted by CHPTRF, stored  as  a  packed  triangular
               matrix.

               On  exit,  if INFO = 0, the (Hermitian) inverse of
               the original matrix, stored as a packed triangular
               matrix. The j-th column of inv(A) is stored in the
               array AP  as  follows:  if  UPLO  =  'U',  AP(i  +
               (j-1)*j/2)  =  inv(A)(i,j)  for 1<=i<=j; if UPLO =
               'L', AP(i  +  (j-1)*(2n-j)/2)  =  inv(A)(i,j)  for
               j<=i<=n.

       IPIV    (input) INTEGER array, dimension (N)
               Details  of  the interchanges and the block struc­
               ture of D as determined by CHPTRF.

       WORK    (workspace) COMPLEX array, dimension (N)

       INFO    (output) INTEGER
               = 0: successful exit

               gal value
               > 0: if INFO = i, D(i,i) = 0; the matrix is singu­
               lar and its inverse could not be computed.


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