DTRTI2(3)      LAPACK routine of NEC Numeric Library Collection      DTRTI2(3)



NAME
       DTRTI2

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



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

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

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

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

           INFO      (output)
                     INFO is INTEGER
                     = 0: successful exit
                     < 0: if INFO = -k, the k-th argument had an illegal value



LAPACK routine                  31 October 2017                      DTRTI2(3)