DDTTRF(3)     ScaLAPACK routine of NEC Numeric Library Collection    DDTTRF(3)



NAME
       DDTTRF  - compute an LU factorization of a complex tridiagonal matrix A
       using elimination without partial pivoting

SYNOPSIS
       SUBROUTINE DDTTRF( N, DL, D, DU, INFO )

           INTEGER        INFO, N

           DOUBLE         PRECISION D( * ), DL( * ), DU( * )

PURPOSE
       DDTTRF computes an LU factorization of a complex tridiagonal  matrix  A
       using  elimination without partial pivoting.  The factorization has the
       form
          A = L * U
       where L is a product of unit lower bidiagonal
       matrices and U is upper triangular with nonzeros in only the main diag-
       onal and first superdiagonal.


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

       DL      (input/output) COMPLEX array, dimension (N-1)
               On  entry, DL must contain the (n-1) subdiagonal elements of A.
               On exit, DL is overwritten by the (n-1) multipliers that define
               the matrix L from the LU factorization of A.

       D       (input/output) COMPLEX array, dimension (N)
               On  entry, D must contain the diagonal elements of A.  On exit,
               D is overwritten by the n diagonal elements of the upper trian-
               gular matrix U from the LU factorization of A.

       DU      (input/output) COMPLEX array, dimension (N-1)
               On  entry,  DU must contain the (n-1) superdiagonal elements of
               A.  On exit, DU is overwritten by the  (n-1)  elements  of  the
               first superdiagonal of U.

       INFO    (output) INTEGER
               = 0:  successful exit
               < 0:  if INFO = -i, the i-th argument had an illegal value
               >  0:   if  INFO = i, U(i,i) is exactly zero. The factorization
               has been completed, but the factor U is exactly  singular,  and
               division  by zero will occur if it is used to solve a system of
               equations.



ScaLAPACK routine               31 October 2017                      DDTTRF(3)