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NAME
     ssptri - compute the inverse of a real symmetric  indefinite
     matrix  A  in  packed  storage  using  the factorization A =
     U*D*U**T or A = L*D*L**T computed by SSPTRF

SYNOPSIS
     SUBROUTINE SSPTRI( UPLO, N, AP, IPIV, WORK, INFO )

     CHARACTER UPLO

     INTEGER INFO, N

     INTEGER IPIV( * )

     REAL AP( * ), WORK( * )



     #include <sunperf.h>

     void ssptri(char uplo, int n, float *sap, int  *ipivot,  int
               *info) ;

PURPOSE
     SSPTRI computes the inverse of a real  symmetric  indefinite
     matrix  A  in  packed  storage  using  the factorization A =
     U*D*U**T or A = L*D*L**T computed by SSPTRF.


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**T;
               = 'L':  Lower triangular, form is A = L*D*L**T.

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

     AP        (input/output) REAL 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 SSPTRF, stored  as  a  packed  triangular
               matrix.

               On exit, if INFO = 0, the (symmetric)  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 SSPTRF.

     WORK      (workspace) REAL array, dimension (N)

     INFO      (output) INTEGER
               = 0: successful exit
               < 0: if INFO = -i, the i-th argument had an  ille-
               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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