parallel execution of loop

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D_coder 2019-3-22

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https://ww2.mathworks.cn/matlabcentral/answers/451748-parallel-execution-of-loop

评论： Walter Roberson 2019-3-23

I have the following structure

for i = 1:N
    
    %some lines of code
    
    for j = 1:M
        
        %some lines of code and M<N
        
    end
end

How do I perform following parallel execution : i = 1 perform j = 1, i = 2 perform j = 1, i = 3 perform j = 1 and then i = 2 perform j = 1 and so on ?

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Adam 2019-3-22

在 MATLAB Online 中打开

I'm not sure I really get your description at the bottom. That basically just boils down to the for loops as you have shown them that you want parallelising?

If you have the Parallel Computing Toolbox then

doc parfor

can do this, depending what is in the body of the for loops. You would usually want to put the parfor on the outer loop. for obvious reasons you can't make both loops parfors.

Walter Roberson 2019-3-23

在 MATLAB Online 中打开

Performing the iterations in the order you request would not be equivalent to doing them in serial.

A = 0;
for i = 1 : 10
    B = 0;
    for j = 1 : 5
        A = A + 1;
        B = B + 1;
    end
end

When i = 2, j = 1, then A has to be 5 if you executed in serial mode. But if all of the j = 1 iterations for each possible i are executed first, as you request, then A would have been incremented to 10.

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