Recommended steps to deal with a slow loop
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Hi,
If a "for loop" is slow and each iteration is taking 2 hours what are the recommended steps that I should follow to deal with this issue?
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Conrad
am 27 Jul. 2012
I would recommend that you first focus on what happens inside the for loop... why is it taking so long? Get a complete breakdown of how much time is spend at every step, then you can decide where you can possibly optimise.
Further details would be great.
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Sean de Wolski
am 27 Jul. 2012
- Listen to mlint. If it is warning you about a variable changing size within a loop, that will slow it down immensely
- Remove every calculation from every loop that does not depend on the loop.
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Sean de Wolski
am 27 Jul. 2012
Use the profiler to identify the bottlenecks. Just run two or three files with profiler and it will show you where to focus your efforts. Some obvious things:
- try/catch is slow. I would try and write the code to avoid those.
- Skip the call to find here:
x0=find(ismember(s2(:,1),ID(k,1)));
- regexp can be slow, perhaps csvread or dlmread?
- Conversions to and from cell is slow (s2=num2cell(nan(size(V,1)-1,size(scol,2)));) avoid this if possible.
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