Parallel Processing code question, with error Subscripted assignment between dissimilar structures
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I am trying to become familiar with the parallel toolbox and wrote what I think is a simple script that is failing and I don't understand why. I have included the code below.
clear all
close all
dataSetSize = 1024;
for x = 1:4:dataSetSize
Data(x).dataSet = rand(128,256);
Data(x+1).dataSet = rand(128,512);
Data(x+2).dataSet = rand(64,128);
Data(x+3).dataSet = rand(32,64);
end
parpool(4);
parfor x=1:dataSetSize
Data(x).plotData = 20*log10(abs(fft(Data(x).dataSet)));
end
I get the error
Error using parallelTest (line 15)
Subscripted assignment between dissimilar structures.
Line 15 is the line of the parfor loop. When I execute this as a regular loop it executes fine. I don't see any dependencies and think this should be able to run in parallel.
Any help would be greatly appreciated.
Thanks
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Accepted Answer
Walter Roberson
on 27 May 2015
You need to initialize the PlotData field before the loop. Even if you initialize it to [] that would be fine. In your code, the result of the parfor is a structure with a different set of fields than the original, and there are problems copying the data back because of that. Don't create new struct fields inside a parfor.
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