strtri(3F)

NAME
     STRTRI - compute the inverse of a real upper or lower triangular matrix A

SYNOPSIS
     SUBROUTINE STRTRI( UPLO, DIAG, N, A, LDA, INFO )

         CHARACTER      DIAG, UPLO

         INTEGER        INFO, LDA, N

         REAL           A( LDA, * )

PURPOSE
     STRTRI computes the inverse of a real upper or lower triangular matrix A.

     This is the Level 3 BLAS version of the algorithm.


ARGUMENTS
     UPLO    (input) CHARACTER*1
             = 'U':  A is upper triangular;
             = 'L':  A is lower triangular.

     DIAG    (input) CHARACTER*1
             = 'N':  A is non-unit triangular;
             = 'U':  A is unit triangular.

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

     A       (input/output) REAL array, dimension (LDA,N)
             On entry, the triangular matrix A.  If UPLO = 'U', the leading
             N-by-N upper triangular part of the array A contains the upper
             triangular matrix, and the strictly lower triangular part of A is
             not referenced.  If UPLO = 'L', the leading N-by-N lower
             triangular part of the array A contains the lower triangular
             matrix, and the strictly upper triangular part of A is not
             referenced.  If DIAG = 'U', the diagonal elements of A are also
             not referenced and are assumed to be 1.  On exit, the
             (triangular) inverse of the original matrix, in the same storage
             format.

     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, A(i,i) is exactly zero.  The triangular matrix
             is singular and its inverse can not be computed.