[yt-dev] rockstar

[Stephen Skory]

Hi all (especially Chris & Matt),

this morning I've spent some time trying to get rockstar to work for
me, and I've made some progress, I think, but I'm getting answers I
don't trust, and a crash, besides, so there's more to be done.

What I've done is to pull and merge Chris' current PR for rockstar
(https://bitbucket.org/yt_analysis/yt/pull-request/247/art-rockstar-camera-updates)
into a copy of the current tip of yt. Then upon that, I've made the
following changes (http://paste.yt-project.org/show/2671/). In
particular, here's the substantive things I've done:

- I modified the part of RockstarHaloFinder.__init__ that finds the
total number of particles to work in parallel (meaning, not all the
particles are loaded on all processors).

- I am running on only one data output in my time series. I think this
is why I've had to comment out one of the ProcessorPool() blocks, but
frankly, I don't really understand the ProcessorPool stuff. If I keep
both blocks, the second one in the sequence complains that there are
no workers available.

- My test data does not have the 'particle_type' field, which the
rockstar wrapper was relying on. I've made a few changes that
basically assume that if there is no 'particle_type' field, everything
is a DM particle (which is the case for my test data). This has
required a few changes in rockstar.py and rockstar_interface.pyx (look
for the rh.dm_type stuff).

With these changes, I can get some stuff to run. Here are the most
interesting lines I see:

[     0s] Accepting connections...
[     0s] Accepted all reader / writer connections.
[     0s] Verified all reader / writer connections.
[     0s] Reading 1 blocks for snapshot 0...
(snip)
reading from particle filename ./inline.0: data0012
[    21s] Transferring particles to writers...
[    22s] Analyzing for halos / subhalos...
[    33s] Constructing merger tree...
[    33s] [Success] Done with snapshot 0.

Immediately after this I see some unhelpful crash error messages.

I do get a "halos_0.0.ascii" file (and some other stuff) in my
xxx_rockstar directory, but the centers of mass for the halos are very
fishy (and likely everything else). I think this might be related to
the fact that I'm getting a crash. I think that the centers are fishy
because, for example, the largest halo in the rockstar text file is no
where near the largest that HOP finds, although they do have a similar
number of particles.

There was a bit of momentum on rockstar a couple weeks ago, and I'm
hoping that we can try to get this thing working. I can share the
dataset I'm using for my tests, if anyone wants it (it's similar to
one of the compendium datasets, if not identical), and my script as
well.

Thanks!

-- 
Stephen Skory
s at skory.us
http://stephenskory.com/
510.621.3687 (google voice)