[yt-dev] memory usage with --parallel and periodic radius

[Michael Kuhlen]

Hi all and Nathan specifically

I've found that the changes having to do with periodic fields are causing
excessive memory usage for me when doing parallel halo profiling, to the
point where I can no longer do analysis that used to work fine on my 24GB
memory workstation.

A simple HaloProfiler script (http://paste.yt-project.org/show/3211/), run
in parallel on 8 processors on the halo catalog obtained from one of my
cosmology simulations, currently almost immediate runs out of memory, while
it used to complete without problems.

I tried to use hg bisect to find the problematic changeset but had to skip
the testing of several revisions because of runtime yt errors, so in the
end bisect only gave me a range of potentially bad revisions:
http://paste.yt-project.org/show/3210/. As you can see, they're all related
to the periodic radius mods from about a month ago.

I tried replicating this with the standard Enzo_64 example dataset from
http://yt-project.org/data/, but I guess that one is too small to produce
this problem on my machine. If you want to see the problem for yourself,
then you can download this tarball (
http://astro.berkeley.edu/~mqk/transfer/RD0003.tar 4.5GB) and run this
script (http://paste.yt-project.org/show/3211/) on it, like so:

$ mpirun -np 8 python ./profile_halos.py --parallel

When I run this with the current tip (ccfe34e70803) the total memory usage
grows to >24GB. With the last good changeset the total memory usage never
gets above ~8.5GB (estimated from top).

It'd be great if we could find out what the problem is and fix it, because
this is a major performance regression for me, that, as I already said, is
seriously impacting my ability to do analysis with the current yt tip. Let
me know if I should file a BB issue about this, and/or if there's some way
I can assist with fixing this.

Cheers,
Mike

-- 
*********************************************************************
*                                                                   *
*  Dr. Michael Kuhlen              Theoretical Astrophysics Center  *
*  email: mqk at astro.berkeley.edu   UC Berkeley                      *
*  cell phone: (831) 588-1468      B-116 Hearst Field Annex # 3411  *
*  skype username: mikekuhlen      Berkeley, CA 94720               *
*                                                                   *
*********************************************************************
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