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



NAME
       DTRTRI

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



PURPOSE
            DTRTRI 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)
                     UPLO is CHARACTER*1
                     = 'U':  A is upper triangular;
                     = 'L':  A is lower triangular.

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



LAPACK routine                  31 October 2017                      DTRTRI(3)