How to use parpool for independent expressions

Question

Ole 2021-9-23

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1459449-how-to-use-parpool-for-independent-expressions

评论： Raymond Norris 2021-9-24

采纳的回答： Mohammad Sami

在 MATLAB Online 中打开

How to evaluate independent expressions in local parpool on laptop.

When I try the code below, the parpool is idle.

How to force matlab to evaluate the expressions in parallel.

x = 1; y =2; z=3;
parpool('local',4)   
s = x + y + z; 
a = 2*x + z; 
w = 3*y + 2*z;  
f = 3*x + 2*z;  

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Raymond Norris 2021-9-24

在 MATLAB Online 中打开

Let me ask you this. Using a pool of workers (i.e. processes) cancels out any implicit threadedness. So will there be any value in doing as your requesting?

To see the impact, try the following:

maxNumCompThreads(1);
tic
< run code >
toc
maxNumCompThreads('auto');
tic
< run code >
toc

Next, run your code using a parallel pool of workers and parfeval (as Mohammad has suggested) and see how close it gets to your timings with maxNumCompThreads set to 'auto'. You might see it's a wash.

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Answer 1

Mohammad Sami 2021-9-24

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1459449-how-to-use-parpool-for-independent-expressions#answer_793949

在 MATLAB Online 中打开

You can use the parfeval function to make these calculations on a worker thread.

x = 1; y =2; z=3;
p=parpool('local',4)   
Fs = parfeval(p,@(x,y,z) x + y + z,1,x,y,z); 
Fa = parfeval(p,@(x,z)2*x + z,1,x,z);
Fw = parfeval(p,@(y,z)3*y + 2*z,1,y,z);  
Ff = parfeval(p,@(x,z)3*x + 2*z,1,x,z);
s = Fs.fetchOutputs;
a = Fa.fetchOutputs;
w = Fw.fetchOutputs;
f = Ff.fetchOutputs;