[Yt-dev] treecode thoughts

Matthew Turk matthewturk at gmail.com
Sat Mar 26 09:16:00 PDT 2011


Hey all,

There's cython.profile support as a decorator, which outputs
cProfile-style stuff, but slows Cython code down substantially.  If
you're doing JUST python code, I've recently been using hotshot with
lineevents=True, which gives line-by-line timings.  pyprof2html is
handy for visualizing it and so is kchachegrind.

-Matt

On Sat, Mar 26, 2011 at 12:11 PM, Sam Skillman <samskillman at gmail.com> wrote:
> I use gprof2dot to visualize the output from python cProfile quite a lot.
>  You may want to try that out:
> http://code.google.com/p/jrfonseca/wiki/Gprof2Dot
>
> It only breaks it down between functions, but it should give an idea of
> where most the time is being spent.
> Sam
> On Sat, Mar 26, 2011 at 11:38 AM, Stephen Skory <stephenskory at yahoo.com>
> wrote:
>>
>> Hi Matt,
>>
>> > >
>> > > In summary, for medium to very large sized clumps (in terms of number
>> > > of
>> > cells), the treecode is showing it's usefulness. My tests are not
>> > complete,
>> > but the break even line with the standard opening angle (==approximation
>> > control) of 1.0, is about 100,000 cells. For example, a spherical clump
>> > with
>> > three levels and 120,000 cells takes 272 seconds with the O(N^2) method,
>> > 175
>> > seconds with the treecode, and has a 0.05% error.
>> >
>> > That's interesting.  To be perfectly honest, I kind of expected it to
>> > perform a bit better.  Any insight where the overhead comes from?
>>
>>
>> I'm not sure. I haven't timed individual steps of the code yet to see if
>> something is unreasonably slow. Any useful tool recommendations are
>> welcomed.
>>
>> > It should be on by default.  What is the performance difference, for a
>> > small/medium clump?  10%?  50%?  Factor of 10?
>>
>>
>> It looks like it's no worse than a factor of two slower for
>> opening_angle=1.0 at around 30,000 cells. I plan on making a figure showing
>> this stuff soon.
>>
>> > Very nice work!  I have reviewed your changes and I think you should
>> > merge them.  This will be a shining addition to the 2.1 release.
>>
>>
>> Thanks for the praise, I appreciate it.
>>
>> > Could you post a script verifying that it works for clumps on the edge
>> > and in the center, to be added to the answer tests?
>>
>>
>> Sure, I can do that.
>>
>>
>> Stephen Skory
>> stephenskory at yahoo.com
>> http://stephenskory.com/
>> 510.621.3687 (google voice)
>>
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>
>
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