<meta http-equiv="Content-Type" content="text/html; charset=utf-8"><div dir="ltr">I think this is a good idea and would be helpful to a lot of people! I have a couple (minor) concerns/questions<div><br></div><div>1. The difference between accessing the attributes of a halo catalog and accessing the attributes of a halo's particles needs to be really well documented and continuously restated throughout any docs examples. In those two lines (below), it took me a little bit to think about whether I'd expect that to return the halo's mass (considering the halo as a "particle") or a list of the masses of the particles that make up the halo - and I've used this machinery a lot! </div><div><br></div><div><div style="font-size:12.8000001907349px">my_halo = ds.halo(some_id)</div><div style="font-size:12.8000001907349px">my_halo["particle_mass"]</div></div><div style="font-size:12.8000001907349px"><br></div><div style="font-size:12.8000001907349px">2. On a similar note, we should be more deliberate with the naming conventions of the various fields in a halo catalog. At the moment, the default mass of the particle is stored as 'particle_mass', which seems misleading if thats also what we want to call the mass of constituent particle field. Maybe something like "particle_mass" vs "halo_mass" and "particle_position_x" vs "halo_position_x"? I haven't completely thought this through, but its at least a question we should consider.</div><div style="font-size:12.8000001907349px"><span style="font-size:12.8000001907349px"><br></span></div><div style="font-size:12.8000001907349px"><span style="font-size:12.8000001907349px">By a similar (but pretty unrelated) token, we also should be more careful about what we store as the halo radius. Right now we store a field "virial_radius" in the halo catalog by default, which I think confuses a lot of users, because of its similarity to the virial_quantities callback. </span></div><div style="font-size:12.8000001907349px"><span style="font-size:12.8000001907349px"><br></span></div><div style="font-size:12.8000001907349px"><span style="font-size:12.8000001907349px">3. Is a data container the right way to go? Is there enough overlap between the functionality we would want from a halo and the functionality of a (generally) geometric subset of some original dataset? Given my lack of familiarity with that infrastructure, I have absolutely no idea.</span></div><div style="font-size:12.8000001907349px"><br></div><div style="font-size:12.8000001907349px">-Hilary</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, May 7, 2015 at 9:15 AM, Ben Thompson <span dir="ltr"><<a href="mailto:bthompson2090@gmail.com" target="_blank">bthompson2090@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div><div><div>Hi Britton.<br></div><div><br></div>Probably should not be too difficult to port across my code for that.<br><br></div>Sorry to also distract from the original topic too. I think the idea is good, but I don't have much experience on the data selector side of things myself, so I do not know how much help I would be on that part in particular.<span class="HOEnZb"><font color="#888888"><br><br></font></span></div><span class="HOEnZb"><font color="#888888">Ben.<br></font></span></div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br><div class="gmail_quote">On Thu, May 7, 2015 at 12:11 PM, Britton Smith <span dir="ltr"><<a href="mailto:brittonsmith@gmail.com" target="_blank">brittonsmith@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Hi Ben,<div><br></div><div>I have added frontends for the outputs of a couple different halo finders now and found it to be pretty straightforward. If you're interested in doing this, you should have a look at either the rockstar or owls_subfind frontends.</div><span><font color="#888888"><div><br></div><div>Britton</div></font></span></div><div><div><div class="gmail_extra"><br><div class="gmail_quote">On Thu, May 7, 2015 at 11:08 AM, Ben Thompson <span dir="ltr"><<a href="mailto:bthompson2090@gmail.com" target="_blank">bthompson2090@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div><div>+1 for this idea. I have essentially been using yt.sphere data contains with the virial radius as my way of querying the particles within the halo. When in fact depending on the halo finder, halos do not necessary have to be spherical. Likewise rockstar and other halo finders also have machinery to tell you what particles are currently in the halo too.<br><br></div>On topic of halo finders, how easy do you guys think would it be to implement other halo finders? Or at least be able to read in the results of other halo finders? With machinery like this, it would potentially be easier to "at least" include the results of other halo finders too. I have been using AHF for a lot of my work recently but am currently working with a custom version of the pynbody halo catalog (pretty much a direct rip but using YT to handle the units upon initialisation). I imagine with machinery like this it would be easier to do so.<br><br></div>Ben.<br></div><div class="gmail_extra"><br><div class="gmail_quote"><div><div>On Thu, May 7, 2015 at 11:57 AM, Britton Smith <span dir="ltr"><<a href="mailto:brittonsmith@gmail.com" target="_blank">brittonsmith@gmail.com</a>></span> wrote:<br></div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div><div><div dir="ltr">Hi everyone,<div><br></div><div>Myself and one other who should be joining this list soon are interested in implementing some new functionality and I would like to solicit some advice.</div><div><br></div><div>What we have are halo catalog datasets that, for the most part, are already loadable in yt. They are loadable in that each individual halo is a particle such that querying the mass field returns the mass of each halo. However, these datasets also store the particles from the simulation snapshot that are the members of each halo. We currently do not have the machinery to query them and this is what we would like to add.</div><div><br></div><div>It seems the most sensible idea is to create a halo data container such that something like the following returns the mass of all the particles in a halo:</div><div><br></div><div>my_halo = ds.halo(some_id)</div><div>my_halo["particle_mass"]</div><div><br></div><div>This is somewhat different from the existing data containers as it is not geometric. The member particles are explicitly known. I don't have much experience with making data containers so I can't tell if this makes things easier or harder. Anyway, this is the plan.</div><div><br></div><div>If anyone has reasons this may be too difficult or simply not work, I would appreciate hearing them. Any general advice or other ideas for making this functionality work would also be welcome.</div><div><br></div><div>Thanks!</div><span><font color="#888888"><div><br></div><div>Britton</div></font></span></div>
<br></div></div>_______________________________________________<br>
yt-dev mailing list<br>
<a href="mailto:yt-dev@lists.spacepope.org" target="_blank">yt-dev@lists.spacepope.org</a><br>
<a href="http://lists.spacepope.org/listinfo.cgi/yt-dev-spacepope.org" target="_blank">http://lists.spacepope.org/listinfo.cgi/yt-dev-spacepope.org</a><br>
<br></blockquote></div><br></div>
<br>_______________________________________________<br>
yt-dev mailing list<br>
<a href="mailto:yt-dev@lists.spacepope.org" target="_blank">yt-dev@lists.spacepope.org</a><br>
<a href="http://lists.spacepope.org/listinfo.cgi/yt-dev-spacepope.org" target="_blank">http://lists.spacepope.org/listinfo.cgi/yt-dev-spacepope.org</a><br>
<br></blockquote></div><br></div>
</div></div><br>_______________________________________________<br>
yt-dev mailing list<br>
<a href="mailto:yt-dev@lists.spacepope.org" target="_blank">yt-dev@lists.spacepope.org</a><br>
<a href="http://lists.spacepope.org/listinfo.cgi/yt-dev-spacepope.org" target="_blank">http://lists.spacepope.org/listinfo.cgi/yt-dev-spacepope.org</a><br>
<br></blockquote></div><br></div>
</div></div><br>_______________________________________________<br>
yt-dev mailing list<br>
<a href="mailto:yt-dev@lists.spacepope.org">yt-dev@lists.spacepope.org</a><br>
<a href="http://lists.spacepope.org/listinfo.cgi/yt-dev-spacepope.org" target="_blank">http://lists.spacepope.org/listinfo.cgi/yt-dev-spacepope.org</a><br>
<br></blockquote></div><br></div>