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dgttrf.f(3)				      LAPACK				      dgttrf.f(3)

NAME
       dgttrf.f -

SYNOPSIS
   Functions/Subroutines
       subroutine dgttrf (N, DL, D, DU, DU2, IPIV, INFO)
	   DGTTRF

Function/Subroutine Documentation
   subroutine dgttrf (integerN, double precision, dimension( * )DL, double precision, dimension(
       * )D, double precision, dimension( * )DU, double precision, dimension( * )DU2, integer,
       dimension( * )IPIV, integerINFO)
       DGTTRF

       Purpose:

	    DGTTRF computes an LU factorization of a real tridiagonal matrix A
	    using elimination with partial pivoting and row interchanges.

	    The factorization has the form
	       A = L * U
	    where L is a product of permutation and unit lower bidiagonal
	    matrices and U is upper triangular with nonzeros in only the main
	    diagonal and first two superdiagonals.

       Parameters:
	   N

		     N is INTEGER
		     The order of the matrix A.

	   DL

		     DL is DOUBLE PRECISION array, dimension (N-1)
		     On entry, DL must contain the (n-1) sub-diagonal 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

		     D is DOUBLE PRECISION 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

		     DU is DOUBLE PRECISION array, dimension (N-1)
		     On entry, DU must contain the (n-1) super-diagonal elements
		     of A.

		     On exit, DU is overwritten by the (n-1) elements of the first
		     super-diagonal of U.

	   DU2

		     DU2 is DOUBLE PRECISION array, dimension (N-2)
		     On exit, DU2 is overwritten by the (n-2) elements of the
		     second super-diagonal of U.

	   IPIV

		     IPIV is INTEGER array, dimension (N)
		     The pivot indices; for 1 <= i <= n, row i of the matrix was
		     interchanged with row IPIV(i).  IPIV(i) will always be either
		     i or i+1; IPIV(i) = i indicates a row interchange was not
		     required.

	   INFO

		     INFO is INTEGER
		     = 0:  successful exit
		     < 0:  if INFO = -k, the k-th argument had an illegal value
		     > 0:  if INFO = k, U(k,k) 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.

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   September 2012

       Definition at line 125 of file dgttrf.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.2				 Tue Sep 25 2012			      dgttrf.f(3)


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