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## NAME

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

```

## SYNOPSIS

```       SUBROUTINE CDTTRF( N, DL, D, DU, INFO )

INTEGER        INFO, N

COMPLEX        D( * ), DL( * ), DU( * )

```

## PURPOSE

```       CDTTRF 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
diagonal 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
triangular 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.
```