File: lu_rightpr.m

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ufsparse 1.2-7
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function [L,U,P] = lu_rightpr (A)
n = size (A,1)
if (n == 1)
    P = 1 ;
    L = 1 ;
    U = A ;
else
    [x,i] = max (abs (A (1:n,1))) ;			      % partial pivoting
    P1 = eye (n) ;
    P1 ([1 i],:) = P1 ([i 1], :) ;
    A = P1*A ;
    u11 = A (1,1) ;					      % (7.10)
    u12 = A (1,2:n) ;					      % (7.11)
    l21 = A (2:n,1) / u11 ;				      % (7.12)
    [L22,U22,P2] = lu_rightpr (A (2:n,2:n) - l21*u12) ;	      % (7.9) or (7.13)
    o = zeros(1,n-1) ;
    L = [ 1 o ; P2*l21 L22 ] ;				      % (7.14)
    U = [ u11 u12 ; zeros(n-1,1) U22 ] ;
    P = [ 1 o ; o' P2] * P1 ;
end