dgttrf.f(3) [centos man page]

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)

Check Out this Related Man Page

DGTTRF(l)								 )								 DGTTRF(l)

NAME

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

SYNOPSIS

       SUBROUTINE DGTTRF( N, DL, D, DU, DU2, IPIV, INFO )

	   INTEGER	  INFO, N

	   INTEGER	  IPIV( * )

	   DOUBLE	  PRECISION D( * ), DL( * ), DU( * ), DU2( * )

PURPOSE

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

ARGUMENTS

       N       (input) INTEGER
	       The order of the matrix A.

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

       IPIV    (output) 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    (output) 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.

LAPACK version 3.0						   15 June 2000 							 DGTTRF(l)

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dgttrf.f(3) [centos man page]

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