ddttrf(3) [debian man page]

DDTTRF(l)						   LAPACK routine (version 2.0) 						 DDTTRF(l)

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 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.

modified LAPACK routine 					    12 May 1997 							 DDTTRF(l)