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function test21
%TEST21 test cholmod2 on diagonal or ill-conditioned matrices
% Example:
% test21
% See also cholmod_test
% Copyright 2007, Timothy A. Davis, http://www.suitesparse.com
fprintf ('=================================================================\n');
fprintf ('test21: test cholmod2 on diagonal or ill-conditioned matrices\n') ;
f = [
72 % HB/bcsstm22
315 % Bai/mhdb416
64 % HB/bcsstm09
71 % HB/bcsstm21
1207 % Oberwolfach/t2dal_e
354 % Boeing/crystm02
1211 % Oberwolfach/t3dl_e
]' ;
for i = f
Prob = ssget (i) %#ok
A = Prob.A ;
n = size (A,1) ;
x = ones (n,2) ;
b = A*x ;
fprintf ('nnz: %d\n', nnz (A)) ;
x1 = A\b ;
x2 = cholmod2 (A,b) ;
s = norm (A,1) * norm (x,1) + norm (b,1) ;
resid1 = norm (A*x1-b,1) / s ;
resid2 = norm (A*x2-b,1) / s ;
err1 = norm (x-x1,1) ;
err2 = norm (x-x2,1) ;
fprintf ('MATLAB resid %6.1e err %6.1e\n', resid1, err1) ;
fprintf ('CHOLMOD resid %6.1e err %6.1e\n', resid2, err2) ;
fprintf ('condest %6.1e\n', condest (A)) ;
end
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