why parfor-loop spend more time for-loop?

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Tao
Tao on 15 Apr 2014
Commented: Tao on 16 Apr 2014
function test_parfor
N = 1e8;
sum_all = 0; % sum all numbers
sum_odd = 0; % sum odd numbers
sum_even = 0; % sum even numbers
tic;
parfor i = 1 : N
sum_all = sum_all + i; % sum all numbers
if mod(i,2)
sum_odd = sum_odd + i; % sum odd numbers
else
sum_even = sum_even + i; % sum even numbers
end %endif
end %endfor
toc;
fprintf('sum_all=%d,\nsum_odd=%d,\nsum_even=%d.\n', ...
sum_all, sum_odd, sum_even);
I have initialized the parpool envionment and run the codes above. However, the parfor-loop took far more time than single for-loop. Why? What is wrong with my codes? Thank you very much! :-)

Answers (1)

Matt J
Matt J on 15 Apr 2014
Did you execute it in a script or a function? Try the latter.
  3 Comments
Matt J
Matt J on 15 Apr 2014
How many cores on your machine? And how many workers in your parpool?
Tao
Tao on 16 Apr 2014
Thank you for your reply. The numCores of my PC is 12. I initialize 12 workers.

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