cpptri(3S)

NAME
     CPPTRI - compute the inverse of a complex Hermitian positive definite
     matrix A using the Cholesky factorization A = U**H*U or A = L*L**H
     computed by CPPTRF

SYNOPSIS
     SUBROUTINE CPPTRI( UPLO, N, AP, INFO )

         CHARACTER      UPLO

         INTEGER        INFO, N

         COMPLEX        AP( * )

IMPLEMENTATION
     These routines are part of the SCSL Scientific Library and can be loaded
     using either the -lscs or the -lscs_mp option.  The -lscs_mp option
     directs the linker to use the multi-processor version of the library.

     When linking to SCSL with -lscs or -lscs_mp, the default integer size is
     4 bytes (32 bits). Another version of SCSL is available in which integers
     are 8 bytes (64 bits).  This version allows the user access to larger
     memory sizes and helps when porting legacy Cray codes.  It can be loaded
     by using the -lscs_i8 option or the -lscs_i8_mp option. A program may use
     only one of the two versions; 4-byte integer and 8-byte integer library
     calls cannot be mixed.

PURPOSE
     CPPTRI computes the inverse of a complex Hermitian positive definite
     matrix A using the Cholesky factorization A = U**H*U or A = L*L**H
     computed by CPPTRF.

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) COMPLEX array, dimension (N*(N+1)/2)
             On entry, the triangular factor U or L from the Cholesky
             factorization A = U**H*U or A = L*L**H, packed columnwise as a
             linear array.  The j-th column of U or L is stored in the array
             AP as follows:  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 (Hermitian) 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.

SEE ALSO
     INTRO_LAPACK(3S), INTRO_SCSL(3S)

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