
sgttrf.f(3) LAPACK sgttrf.f(3)
NAME
sgttrf.f 
SYNOPSIS
Functions/Subroutines
subroutine sgttrf (N, DL, D, DU, DU2, IPIV, INFO)
SGTTRF
Function/Subroutine Documentation
subroutine sgttrf (integerN, real, dimension( * )DL, real, dimension( * )D, real, dimension( *
)DU, real, dimension( * )DU2, integer, dimension( * )IPIV, integerINFO)
SGTTRF
Purpose:
SGTTRF 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 REAL array, dimension (N1)
On entry, DL must contain the (n1) subdiagonal elements of
A.
On exit, DL is overwritten by the (n1) multipliers that
define the matrix L from the LU factorization of A.
D
D is REAL 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 REAL array, dimension (N1)
On entry, DU must contain the (n1) superdiagonal elements
of A.
On exit, DU is overwritten by the (n1) elements of the first
superdiagonal of U.
DU2
DU2 is REAL array, dimension (N2)
On exit, DU2 is overwritten by the (n2) elements of the
second superdiagonal 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 kth 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 sgttrf.f.
Author
Generated automatically by Doxygen for LAPACK from the source code.
Version 3.4.2 Tue Sep 25 2012 sgttrf.f(3) 
