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Am I running in parallel? (best way to check)

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Is there a better way than this?
function answer = is_in_parallel ()
try
answer = ~isempty(getCurrentTask());
catch err
if ~strcmp(err.identifier, 'MATLAB:UndefinedFunction')
rethrow(err);
end
answer = false;
end
end
  8 Comments
Felipe G. Nievinski
Felipe G. Nievinski on 8 Jan 2013
Other possibilities that I considered for checking were:
~isempty(ver('distcomp'))
and:
(matlabpool('size') > 0)
but neither seemed better than:
~isempty(getCurrentTask())
Tom Holden
Tom Holden on 8 Apr 2022
getCurrentTask throws an error within a thread based parallel pool. So perhaps answer should be true if an error is thrown!

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Accepted Answer

Jan
Jan on 9 Jan 2013
Let me summarize the current discussion:
No. There seems to be no better solution.

More Answers (3)

埃博拉酱
埃博拉酱 on 3 Apr 2023
Edited: 埃博拉酱 on 3 Apr 2023
parallel.internal.pool.isPoolThreadWorker||~isempty(getCurrentJob))
This code can robustly return true if and only if run on a parallel worker either as threads or processes.

Tom Holden
Tom Holden on 8 Apr 2022
~usejava( 'desktop' ) seems to work even on thread based parallel pools.

Daniel Shub
Daniel Shub on 9 Jan 2013
MATLAB has a number of such functions that tell you about the state of the world (e.g., ispc, isdeployed, isjava). These functions seem to be necessary since there are thing you can/cannot do when they are true/false. I am not sure that something like isparallel is needed. It seems you are looking for something more like isheadless. That said, I am not sure this is the best approach. I am guessing here, but it sounds like your two uses cases are something like
parfor = 1:N
myFuncThatComputesAndPrints;
end
and
for = 1:N
myFuncThatComputesAndPrints;
end
and you want myFuncThatComputesAndPrints to know if it is running headless so that it will suppress the printing. I would suggest that you modify myFuncThatComputesAndPrints to take a flag to determine if it should print giving you
printFlag = true;
parfor = 1:N
myFuncThatComputesAndPrints(printFlag);
end
myFuncThatOnlyPrints;
and
printFlag = false;
for = 1:N
myFuncThatComputesAndPrints(printFlag);
end
This would allow you to expand the cases where you choose not to print.
  5 Comments
Felipe
Felipe on 9 Jan 2013
How would you implement isparallel that would work if called outside the parfor? I don't think any of ~isempty(ver('distcomp')), (matlabpool('size') > 0), or ~isempty(getCurrentTask()) would work.
Jan
Jan on 9 Jan 2013
getCurrentTask() works outside a PARFOR loop and replies [].

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