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Undocumented profiler options

The Matlab profiler is a powerful tool for debugging performance-related issues in Matlab applications. However, it also has some undocumented options that facilitate other forms of debugging, namely memory bottlenecks and JIT (Just-In-Time compilation) problems.

To turn on memory stats in the profile report, run this (only once is necessary - will be remembered for future profiling runs):

profile -memory on;
profile('-memory','on');  % an alternative

To turn on JIT information, run this (again, only once is necessary, prior to profile report):

setpref('profiler','showJitLines',1);

You will then see additional JIT and memory (allocated, freed and peak) information displayed in the profile report, as well as the options to sort by allocated, freed and peak memory:


Profile report with memory & JIT infoProfile report with memory & JIT info

Profile report with memory & JIT info

Profile report with memory & JIT info

For those interested, the references to these two options appear within the code of profview.m (line 1199 on R2007b), for the JIT option:

showJitLines = getpref('profiler','showJitLines',false);

…and profile.m (lines 163-165 on R2007b), for the memory option:

if memory ~= -1
    callstats('memory', memory);
end

Note that there appears to be two undocumented additional memory-related options in profile.m (lines 311-312):

options = {'detail', 'timer', 'history', 'nohistory', 'historysize', ...
           'timestamp', 'memory', 'callmemory', 'nomemory' };

However, ‘-nomemory’ appears to simply turn the memory stats collection off, and ‘-callmemory’ is not recognized because of a bug in line 349, which looks for ‘callnomemory’…:

    case 'callnomemory'   % should be 'callmemory'
           memory = 2;

When this bug is fixed, we see that we get only partial memory information, so the ‘-callmemory’ option is really not useful - use ‘-memory’ instead.

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This entry was posted on Thursday, April 2nd, 2009 at 3:24 pm and is filed under Desktop, Medium risk of breaking in future versions, Memory, Stock Matlab function. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.

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5 Responses to “Undocumented profiler options”

  1. Scott Hirsch Scott Hirsch says:
    April 3, 2009 at 4:17 am

    Yair -

    Thanks for another interesting post. I’d like to share a couple of comments:

    - We would love feedback on the memory profiling feature. We know there’s a lot of interest in tools to help figure out where and how memory is chewed up in code, but it turns out to be not so obvious as to what information to present and how. I’ll keep an eye out here for comments, or readers can feel free to email me directly. My address is on my MATLAB Central page.

    - I would advise a bit of caution when working with the JIT profiler results. We turned them off after MATLAB 6.5 primarily because the JIT was such a moving target (changing every release) that we really didn’t want to encourage users to code against it. That being said, your readers all know the standard warning that comes with your posts - so have fun poking around!!

  2. Mark Westwood Mark Westwood says:
    April 8, 2009 at 12:40 am

    Yair

    This is rapidly becoming one of my favourite blog sites. keep up the excellent work.

    Mark

  3. Marcel Marcel says:
    May 20, 2009 at 6:07 am

    Profiling the memory sounds really interresting - unfortunately it does NOT work on my computer (Win XP, Maltab R2009a)

    Marcel

  4. tic / toc - undocumented option | Undocumented Matlab tic / toc - undocumented option | Undocumented Matlab says:
    May 22, 2009 at 6:12 am

    [...] I have recently discussed undocumented features in Matlab’s built-in profiler. Another tool often used for ad-hoc performance profiling of Matlab code are the built-in duo functions tic and toc [...]

  5. Mark Mark says:
    July 12, 2009 at 11:40 pm

    Good Work

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