[Yt-dev] treecode thoughts

Sam Skillman samskillman at gmail.com
Sat Mar 26 09:11:04 PDT 2011


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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