parfor error with 3D matrix

Question

sunny kant 2022-1-30

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https://ww2.mathworks.cn/matlabcentral/answers/1639050-parfor-error-with-3d-matrix

评论： Matt J 2022-1-31

Hello everyone,

I am using the parfor loop for the 3D matrix. When I am executing my parfor loop and getting this error "Error: The variable TEST1 in a parfor cannot be classified. See Parallel for Loops in MATLAB, "Overview". I am replacing the zero value with nan in the loop. Any suggestion regarding this. Your help in this regard will be highly appreciated.

data  = rand (20,10,10);
data1 = rand (20,10,10);
parfor ii=1:20
    ii
    for jj=1:10
        jj
            TEST1 (ii,jj,:) = data(ii,jj,:).*data1 (ii,jj,:);
            TEST1 (TEST1==0) = nan;
        end
 end

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Answer 1

Matt J 2022-1-30

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https://ww2.mathworks.cn/matlabcentral/answers/1639050-parfor-error-with-3d-matrix#answer_884845

在 MATLAB Online 中打开

Move that line outside the loop.

parfor ii=1:20
    ii
    for jj=1:10
        jj
            TEST1 (ii,jj,:) = data(ii,jj,:).*data1 (ii,jj,:);
        end
end
TEST1 (TEST1==0) = nan;

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Answer 2

sunny kant 2022-1-31

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https://ww2.mathworks.cn/matlabcentral/answers/1639050-parfor-error-with-3d-matrix#answer_885180

Thanks you Matt for your suggestion on the code. However, I am applied the same thing, but when I am applying TES1 (TEST1==0) = nan inside the parfor loop in the code, it gives error. Can you suggest me that why it is happing.

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Matt J 2022-1-31

编辑：Matt J 2022-1-31

在 MATLAB Online 中打开

Additionally

TEST1 (TEST1==0) = nan;

is an operation that Matlab already does in a fast, parallelized manner without explicit loops. You should reserve parfor only for things that cannot easily be replaced with vectorized expressions.

Matt J 2022-1-31

sunny kant's comment moved here

Thanks Walter for explaining me why my code is not working. As you suggested, I appllied for my code, and now it is working. Thanks for your suggestion on my code and clearing my doubts.

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