fetchOutputs() results in an error when the preceding parfeval() was called using the backgroundPool

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Lionel Pöffel 2021-12-18

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https://ww2.mathworks.cn/matlabcentral/answers/1613800-fetchoutputs-results-in-an-error-when-the-preceding-parfeval-was-called-using-the-backgroundpool

评论： Lionel Pöffel 2021-12-20

I have a code piece that works fine:

function [ServerVersInfo,VersInfoObtained,ExcInfo]=GetVersionInfoFromServer(URL)
    %init outputs 
    try
        %access server, update outputs accordingly
    catch ME
        %set fall-back values for outputs
    end
end
%calling code
p = gcp('nocreate');
if isempty(p)
    p = parpool('local',1);
end
FunHandle = parfeval(p,@GetVersionInfoFromServer,3,StoredUrl);
% wait until FunHandle.State is 'finished'...
[LatestVersInfo,VersInfoObtained,ExcInfo]=fetchOutputs(FunHandle);

When I just replace the pool from the parallel computing toolbox with the backgroundPool, the fetchOutputs throws a MATLAB:parallel:future:ExecutionErrors failure. What's the difference?

(P.S. I tried the backgroundPool because starting the pool from the parallel computing toolbox takes a huge amount of time...)

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Edric Ellis 2021-12-20

Can you show us the full error message you get from fetchOutputs? The error identifier you mention is a generic one that "wraps" all errors that happen on the workers. It's probable that the code you're trying to run on the workers isn't supported for thread-based pools - see the doc for more.

Lionel Pöffel 2021-12-20