Problem with parfor loop due to some variable that cannot be classified.

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Patrick Mboma 2023-4-5

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https://ww2.mathworks.cn/matlabcentral/answers/1942034-problem-with-parfor-loop-due-to-some-variable-that-cannot-be-classified

编辑： Matt J 2023-4-6

采纳的回答： Matt J

在 MATLAB Online 中打开

I am unable to specify a parfor loop that works due to some variable that matlab cannot classify

I tried to implement the following function

function somefunction(N,NWorkers)
counts=zeros(1,actualNworkers);
P=myprogress(N,actualNworkers);
parfor (isim=1:N,NWorkers)                     
    local_labindex=1;
    if NWorkers    
        local_labindex=labindex;
    end
    counts(local_labindex)=counts(local_labindex)+1;
    send(P,[local_labindex,counts(local_labindex)])
end
end

But Matlab complains that "The PARFOR loop cannot run due to the way counts is used"

When this failed, I tried to use a cell array instead of a vector. But that didn't work either. Finally I tried to implement a nested function as shown below but it still does not work

function somefunction(N,NWorkers)
counts=zeros(1,actualNworkers);
P=myprogress(N,actualNworkers);
parfor (isim=1:N,NWorkers)                     
    local_labindex=1;
    if NWorkers    
        local_labindex=labindex;
    end
    o=increment(local_labindex);
    send(P,[local_labindex,o])
end
function o=increment(index)          
counts(index)=counts(index)+1;
o=counts(index);
end
end

But this time the error message is : "The nested INCREMENT cannot be called from within a PARFOR loop"

Is there any workaround this problem?

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Patrick Mboma 2023-4-5

I have looked at that list but I could not find a solution to my problem that's why I posted it. I need to keep track of the number of iterations performed by each worker

Patrick Mboma 2023-4-5

编辑：Patrick Mboma 2023-4-5

As to what I am trying to do with the counts variable, I would like to take the sum to evaluate how far along the process has come.

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采纳的回答

Matt J 2023-4-5

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1942034-problem-with-parfor-loop-due-to-some-variable-that-cannot-be-classified#answer_1210004

编辑：Matt J 2023-4-5

在 MATLAB Online 中打开

It might be easier just to use for-drange loop.

spmd
    counts=0;
    for i=drange(1:N)
        counts=counts+1;
    end
end
counts{:}

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Patrick Mboma 2023-4-6

I guess this could work. One last question, if I may : Would this code work even if there are no workers?

Matt J 2023-4-6

编辑：Matt J 2023-4-6

You could try and see. Even if it does work, it might be advisable to check first to see if a pool is open before doing anything. If no pool is open, the task becomes trivial.

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