1function test_qr
2%TEST_QR test various QR factorization methods
3%
4% Example:
5%   test_qr
6% See also: testall
7
8% Copyright 2006-2012, Timothy A. Davis, http://www.suitesparse.com
9
10index = ssget ;
11[ignore f] = sort (max (index.nrows,index.ncols)) ;
12
13% f = 276
14% f = 706
15f = f (1:100) ;
16
17for i = f
18
19    % Prob = ssget (i,index)
20    Prob = ssget (i) ;
21    disp (Prob) ;
22    A = Prob.A ;
23    [m n] = size (A) ;
24    if (m < n)
25        A = A' ;
26    end
27    [m n] = size (A) ;
28    if (sprank (A) < n | ~isreal (A))                                       %#ok
29        continue ;
30    end
31
32    [V,beta,p,R1,q] = cs_qr(A) ;
33    A = A (p,q) ;
34    parent = etree (A, 'col') ;                                             %#ok
35
36    R0 = qr (A) ;
37    R2 = qr_givens (full (A)) ;
38    R3 = qr_givens_full (full (A)) ;
39
40    subplot (2,2,1) ; cspy (R0) ; title ('matlab') ;
41    subplot (2,2,2) ; cspy (R3) ; title ('qr-full') ;
42    subplot (2,2,3) ; cspy (R2) ; title ('qr-givens') ;
43    subplot (2,2,4) ; cspy (R1) ; title ('cs-qr') ;
44
45    e0 = norm (A'*A-R0'*R0,1) / norm (A,1) ;
46    e1 = norm (A'*A-R1'*R1,1) / norm (A,1) ;
47    e2 = norm (A'*A-R2'*R2,1) / norm (A,1) ;
48    e3 = norm (A'*A-R3'*R3,1) / norm (A,1) ;
49    fprintf ('error %6.2e %6.2e %6.2e %6.2e\n', e0, e1, e2, e3) ;
50    drawnow
51    if (e0 > 0 && (e1 > e0*1e3 | e2 > e0*1e3))                              %#ok
52        pause
53    end
54end
55