DTRTI2(3)                  MathKeisan LAPACK routine                 DTRTI2(3)



NAME
       DTRTI2 - 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 ref-
               erenced.  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



 LAPACK routine (version 3.1)    November 2006                       DTRTI2(3)