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