dtrti2(3F)

NAME
     DTRTI2 - compute the inverse of a real upper or lower triangular matrix

SYNOPSIS
     SUBROUTINE DTRTI2( UPLO, DIAG, N, A, LDA, INFO )

         CHARACTER      DIAG, UPLO

         INTEGER        INFO, LDA, N

         DOUBLE         PRECISION A( LDA, * )

PURPOSE
     DTRTI2 computes the inverse of a real upper or lower triangular matrix.

     This is the Level 2 BLAS version of the algorithm.


ARGUMENTS
     UPLO    (input) CHARACTER*1
             Specifies whether the matrix A is upper or lower triangular.  =
             'U':  Upper triangular
             = 'L':  Lower triangular

     DIAG    (input) CHARACTER*1
             Specifies whether or not the matrix A is unit triangular.  = 'N':
             Non-unit triangular
             = 'U':  Unit triangular

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

     A       (input/output) DOUBLE PRECISION 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 = -k, the k-th argument had an illegal value