Update struct field in parfor

I'm wondering hwo to go around the issue below (this is a simplified version of my code)

method = struct('Len', 1);

parfor nf = 1:3

method.Len = nf^2;

res(nf) = mean(nf+randn(method.Len, 1));

end

The issue is that the struct field cannot be updated within parfor. Is there any workaround to update struct field in a parfor?

Answer 1

[Voss]

I don't know whether it's feasible in your actual code, but you might try making method an array of structs and accessing one element of method within the parfor loop:

try
    method = struct('Len', 1)
    parfor nf = 1:3
        method.Len = nf^2;
        res(nf) = mean(nf+randn(method.Len, 1));
    end
catch ME
    disp(ME.message);
end

method = struct with fields:
    Len: 1

Error: Unable to classify the variable 'method' in the body of the parfor-loop. For more information, see Parallel for Loops in MATLAB, "Solve Variable Classification Issues in parfor-Loops".

method = struct('Len', num2cell(ones(1,3)))

method = 1×3 struct array with fields:
    Len

parfor nf = 1:3
    method(nf).Len = nf^2;
    res(nf) = mean(nf+randn(method(nf).Len, 1));
end
disp(res);

    0.6226    2.1194    2.9470

[Amir Tadayon]

Thanks Benjamin. This workaround works for me. The way I use your idea was to make an array of struct and update the desired field before parfor.