Broadcast Variable Warning in MATLAB Parallel Computing Toolbox

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Kareem Elgindy 2022-4-15

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评论： Kareem Elgindy 2022-5-16

采纳的回答： Matt J

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When I ran a MATLAB code using MATLAB Parallel Computing Toolbox, I got messages like:

The entire array or structure 'a' is a broadcast variable. This might result in unnecessary communication overhead.

The entire array or structure 'b' is a broadcast variable. This might result in unnecessary communication overhead.

The entire array or structure 'L' is a broadcast variable. This might result in unnecessary communication overhead.

I then got lost. The code is still running though, but I don't know what to do exactly to avoid the messages above. Below is a description of the main part of my code:

a = (5:5:100)'; b = (-0.4:0.1:2)'; L = (0.25:0.25:10)'; la = length(a); lb = length(b); lL = length(L);
parfor jj = 1:2
    err1 = zeros(la,lb,lL);
    for i = 1:la
        if jj == 1, bla bla bla; else, bla bla bla; end
        for j = 1:lb
            for k = 1:lL
                err1(i,j,k) = methods(a(i),b(j),L(k));
            end
        end
    end
end

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采纳的回答

Matt J 2022-4-15

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编辑：Matt J 2022-4-15

In this case, the warnings can probably be ignored because a, b, and L are very small.

However, I don't really understand the parallelization stratgy, since the outer parfor loop is very short, and you seem to be doing almost nothing with the loop variable jj. If the intensive work is being done by methods(), I would think you would want to paralleilize over (i,j,k).

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Matt J 2022-4-15

编辑：Matt J 2022-4-15

在 MATLAB Online 中打开

I still need err1 as a matrix of 3 dimensions to do further postprocessing using commands like squeeze along the i dimension, etc. So, reshape here remains useful as suggested by

It should have been 3-dimensional from the beginning and remained so throughout. The shape was established in the declaration line,

err1 = zeros(la,lb,lL);

Kareem Elgindy 2022-5-16