1function [L,U,P] = lu_rightpr (A)
2%LU_RIGHTPR recursive right-looking LU, with partial pivoting.
3%
4% Example:
5%   [L,U,P] = lu_rightpr (A)
6% See also: cs_demo
7
8% Copyright 2006-2012, Timothy A. Davis, http://www.suitesparse.com
9
10n = size (A,1) ;
11if (n == 1)
12    P = 1 ;
13    L = 1 ;
14    U = A ;
15else
16    [x,i] = max (abs (A (1:n,1))) ;                           % partial pivoting
17    P1 = eye (n) ;
18    P1 ([1 i],:) = P1 ([i 1], :) ;
19    A = P1*A ;
20    u11 = A (1,1) ;                                           % (6.10)
21    u12 = A (1,2:n) ;                                         % (6.11)
22    l21 = A (2:n,1) / u11 ;                                   % (6.12)
23    [L22,U22,P2] = lu_rightpr (A (2:n,2:n) - l21*u12) ;       % (6.9) or (6.13)
24    o = zeros(1,n-1) ;
25    L = [ 1 o ; P2*l21 L22 ] ;                                % (6.14)
26    U = [ u11 u12 ; o' U22 ] ;
27    P = [ 1 o ; o' P2] * P1 ;
28end
29