use of cell arrays to store matrices... but parfor gives an error

Question

Michael 2013-3-15

2
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/67339-use-of-cell-arrays-to-store-matrices-but-parfor-gives-an-error

Hi,

I've got a loop which creates three matrices, and I want to store these for each iteration. Previously I've been saving them as indexed files, but I've just discovered cell arrays which appear to be ideal for this purpose.

My code looks like this:

mat_array = cell(3,50);
parfor i = 1:50
    [A,B,C] = matrixgenerator(~);
    mat_array {1,i} = A;
    mat_array {2,i} = B;
    mat_array {3,i} = C;
end

However, I'm getting an error message that mat_array is "indexed in different way, potentially causing dependencies between iterations". I don't understand this error, and don't see where any conflict could arise. Can anyone help me with a workaround?

Thanks

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Answer 1

Edric Ellis 2013-3-15

3
链接

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https://ww2.mathworks.cn/matlabcentral/answers/67339-use-of-cell-arrays-to-store-matrices-but-parfor-gives-an-error#answer_78774

在 MATLAB Online 中打开

Try:

mat_array = cell(3,50);
parfor i = 1:50
  [a,b,c] = matrixgenerator(~);
  mat_array(:,i) = {a,b,c};
end

In this way, you're performing a single indexing operation into mat_array, in a way that the PARFOR infrastructure can understand (i.e. the subscripts are a combination of the loop variable, and the literal ':').

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Michael 2013-3-15

This works very well, thank you. Out of curiosity, why have the brackets been switched to normal () ? Am I saving a 3x1 cell array {A,B,C} in a single cell of mat_array now?

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