# FreeBSD Manual Pages

```CDTTRF - compute an LU factorization of	a complex tridiagonal ma-
trix A using elimination without partial pivoting SUBROUTINE CDT-
TRF( N,	DL, D, DU, INFO	)
INTEGER INFO, N
COMPLEX  D(	 * ), DL( * ), DU( * ) CDTTRF computes an LU fac-
torization 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.

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 ele-
ments 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  superdiago-
nal 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  divi-
sion  by zero will occur if it is used to solve	a system of equa-
tions.

```