CTRTRI  -  compute the inverse of a complex upper or lower
       triangular matrix A


SYNOPSIS

       SUBROUTINE CTRTRI( UPLO, DIAG, N, A, LDA, INFO )

           CHARACTER      DIAG, UPLO

           INTEGER        INFO, LDA, N

           COMPLEX        A( LDA, * )


PURPOSE

       CTRTRI computes the inverse of a complex  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) COMPLEX 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  ref­
               erenced  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  ille­
               gal value
               >  0:  if  INFO  = i, A(i,i) is exactly zero.  The

               not be computed.


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