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function test25
%TEST25 test sdmult on a large matrix
% Example:
% test25
% See also cholmod_test
% Copyright 2007, Timothy A. Davis, http://www.suitesparse.com
fprintf ('=================================================================\n');
fprintf ('test25: test sdmult on a large matrix\n') ;
Prob = ssget (936) ;
A = Prob.A ;
n = size (A,1) ;
nz = nnz (A) ;
fprintf ('\nTest matrix: %d-by-%d, nnz %d\n', n, n, nz) ;
Z = rand (n, 500) ;
fprintf ('\nA*X where X is %d-by-k\n', n) ;
for k = [0:10 10:10:50 100:100:500]
X = Z (:, 1:k) ;
tic ;
D = A*X ;
t1 = toc ;
tic ;
C = sdmult (A,X) ;
t2 = toc ;
err = norm (C-D,1) ;
fprintf (...
'k: %3d time: MATLAB %8.2f CHOLMOD %8.2f speedup %8.2f err %6.0e',...
k, t1, t2, t1/t2, err) ;
fl = 2*nz*k ;
fprintf (' mflop: MATLAB %8.1f CHOLMOD %8.1f\n', 1e-6*fl/t1, 1e-6*fl/t2) ;
clear C D X
end
fprintf ('\nFor comparison, here is CHOLMOD''s x=A\\b time:\n') ;
for k = [1 100:100:500]
B = Z (:, 1:k) ;
tic
x = cholmod2 (A,B) ;
t2 = toc ;
err2 = norm (sdmult(A,x)-B,1) ;
fprintf (...
'CHOLMOD x=A\\b time: %8.2f (b is n-by-%d) resid %6.0e\n', t2, k, err2) ;
clear x B
end
b = Z (:,1) ;
clear Z
tic
x = A\b ;
t1 = toc ;
err1 = norm (A*x-b,1) ;
fprintf ('\nMATLAB x=A\\b time: %8.2f (b is n-by-1) resid %6.0e\n', t1, err1) ;
fprintf ('test25 passed\n') ;
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