MATLAB: Program runtime question

runtime

Hi,

I have a program that (for what I've done so far) takes a long time to run (~4s per loop). In the final version of the code I will be performing hundreds of loops. Would it be quicker if I assigned parts of the code as functions, or would this actually increase the run time?

Thanks

Richard

Best Answer

It is difficult to predict exactly how MATLAB will optimize code. Especially before 2010b, the details how how the code was written in the file could make a substantial difference. This is one of those "You'd have to try it and see" matters.

Have you used the profiler to track down the portion of your code that is taking a lot of time?

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maxNumCompThreads
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How many cores your code actually uses on any given code is far more difficult. MATLAB can sometimes launch extra threads for large problems, but ONLY if it decides there will be a gain in so doing. So any given code may vary in the number of cores it will end up using. With some effort, I can force all of my cores to run flat out, but most simple computations never launch any additional cores.

I would suggest that you test run your code, watching a system monitor that will tell how many cores are active for MATLAB. How you do that will depend on what computer you are using. On my Mac, it is the activity monitor utility that I would use.

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You would have to change the program itself to display its own progress. You can do this very simply with DISP, or you could use the progress bar shown by WAITBAR. Your function should be able to work out roughly how far through it is by counting iterations of its main loop.

It makes sense to save the state of your computation periodically, using the SAVE function. Call this every N iterations of the main loop, where you choose N to make a reasonable interval. You should probably save to a sequence of files, or at least to two files alternately, to protect against the computer going down during a save. You need to ensure that SAVE has access to all the variables that you need to save in order to restart the computation. Then, if you need to restart the computation, you can use LOAD to restore the latest state that was saved.

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