Undocumented Matlab

Undocumented profiler options

Thursday, April 2nd, 2009

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 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.

Related posts:

1. tic / toc – undocumented option Matlab's built-in tic/toc functions have an undocumented option enabling multiple nested clockings...
2. Undocumented scatter plot behavior The scatter plot function has an undocumented behavior when plotting more than 100 points: it returns a single unified patch object handle, rather than a patch handle for each specific point as it returns with 100 or less points....
3. cellfun – undocumented performance boost Matlab's built-in cellfun function has an undocumented option to significantly improve performance in some cases....
4. ismembc – undocumented helper function Matlab has several undocumented internal helper functions that can be useful on their own in some cases. This post presents the ismembc function....
5. Undocumented XML functionality Matlab's built-in XML-processing functions have several undocumented features that can be used by Java-savvy users...
6. Undocumented feature() function Matlab's undocumented feature function enables access to some internal experimental features...

Tags: callstats, Memory, performance, profiler

Categories: Desktop, Medium risk of breaking in future versions, Memory, Stock Matlab function

This entry was posted on Thursday, April 2nd, 2009 at 3:24 pm PST
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7 Responses to “Undocumented profiler options”

1. 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 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 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 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 says:

   July 12, 2009 at 11:40 pm

   Good Work
6. Matthew Davidson says:

   March 29, 2010 at 12:13 pm

   It doesn’t work for me in 2007B, OS X 10.5. It gives me the following error from callstats.m: “Support for memory tracking is not available with the current memory manager.

   This is unfortunate, because lack of memory profiling is one of Matlab’s biggest performance gaps. As someone who works with massive neuroimaging data sets every day, good memory use is more important to me than CPU performance. Shaving an hour or two off an analysis is nice, but using too much memory means my analysis won’t even finish.

   As an ex-professional programmer, I’d seriously considered making and selling something like this as an add-on if I wasn’t in grad school.

   Maybe in that far-off utopia of infinite funding, I can convince my advisors to buy all the necessary copies of later matlab versions.
7. Yair Altman says:

   March 30, 2010 at 10:42 am

   @Matthew – please read Scott Hirsch’s comment above. Scott is the Matlab product manager at MathWorks and says that they “would love feedback on the memory profiling feature”. Perhaps you could contact him via the attached link and explain your use-case. There might be a workaround for your Matlab version/platform. Even if not, it might benefit other users who have similar issues. If you learn anything new, please do post it here.

   <pre lang="matlab">
   a = magic(3);
   sum(a)
   </pre>