1function test27
2%TEST27 test cs_qr, cs_utsolve, cs_qrsol
3%
4% Example:
5%   test27
6% See also: testall
7
8% Copyright 2006-2012, Timothy A. Davis, http://www.suitesparse.com
9
10clear functions
11rand ('state', 0) ;
12
13Prob = ssget ('HB/ibm32') ;
14A = Prob.A ;
15A = A (1:10,:) ;
16[m n] = size (A) ;
17
18[V,Beta,p,R,q] = cs_qr (A') ;
19
20b = rand (m,1) ;
21
22Rm = R (1:m,1:m) ;
23
24bq = b (q) ;
25rtbq = Rm' \ bq ;
26
27rt2 = cs_utsolve (Rm, bq) ;
28
29norm (rtbq - rt2)
30
31x = [rt2 ; zeros(n-m,1)] ;
32
33for k = m:-1:1
34    x = x - V(:,k) * (Beta (k) * (V (:,k)' * x)) ;
35end
36
37x (p) = x ;
38
39norm (A*x-b)
40
41x2 = cs_qrsol (A,b) ;
42
43norm (A*x2-b)
44norm (x-x2)
45