Parfor or parfeval, what is better?

Question

Andrea Stevanato 2018-7-14

0
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https://ww2.mathworks.cn/matlabcentral/answers/410364-parfor-or-parfeval-what-is-better

回答： Edric Ellis 2018-7-16

if I have some code that could be writed in same way with parfeval o parfor, what i have to use? What is better? Which is more advantageous, faster... e.g:

parfor i = 1:n
  result = function(data);
end

or

for i = 1:n
  F(i) = parfeval(@function, 1, data);
end
for i = 1:n
  [index, value] = fetchNext(F);
end

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Rik 2018-7-14

I couldn't find any comparisons with a quick search, although I did find that parfeval is (or used to be?) 'plagued by memory a leak'. I checked the release notes for mentions of parfeval, but nothing popped up.

In general I would assume that parfor is a better choice, but that might be a knee jerk reaction because of the feval part of its name.

Edric Ellis 2018-7-16

The memory leak described in that bug report is shown as being fixed in R2015a.

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Answer 1

Edric Ellis 2018-7-16

4
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https://ww2.mathworks.cn/matlabcentral/answers/410364-parfor-or-parfeval-what-is-better#answer_328944

At least some of the trade-offs are:

parfor is generally easier to use, and the code probably looks much more like your serial code
parfor loops can be used by people who don't have Parallel Computing Toolbox
parfor loops perform a degree of load-balancing to try and minimise overheads
parfeval gives you complete control over how the work is chunked up for the workers
parfeval is asynchronous, and lets the MATLAB client get on with other stuff while the workers are busy (e.g. updating plots or other visualisations)