spotri(3S)

NAME
     SPOTRI - 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
     SPOTRF

SYNOPSIS
     SUBROUTINE SPOTRI( UPLO, N, A, LDA, INFO )

         CHARACTER      UPLO

         INTEGER        INFO, LDA, N

         REAL           A( LDA, * )

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
     SPOTRI 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
     SPOTRF.

ARGUMENTS
     UPLO    (input) CHARACTER*1
             = 'U':  Upper triangle of A is stored;
             = 'L':  Lower triangle of A is stored.

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

     A       (input/output) REAL array, dimension (LDA,N)
             On entry, the triangular factor U or L from the Cholesky
             factorization A = U**T*U or A = L*L**T, as computed by SPOTRF.
             On exit, the upper or lower triangle of the (symmetric) inverse
             of A, overwriting the input factor U or L.

     LDA     (input) INTEGER
             The leading dimension of the array A.  LDA >= max(1,N).

     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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