dgttrf.f man page

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.

Referenced By

dgttrf(3) is an alias of dgttrf.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK