[yt-dev] advice on implementing halo member particle loading

[Britton Smith]

Hi Ben,

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.

Britton

On Thu, May 7, 2015 at 11:08 AM, Ben Thompson <bthompson2090 at gmail.com>
wrote:

> +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.
>
> 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.
>
> Ben.
>
> On Thu, May 7, 2015 at 11:57 AM, Britton Smith <brittonsmith at gmail.com>
> wrote:
>
>> Hi everyone,
>>
>> 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.
>>
>> 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.
>>
>> 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:
>>
>> my_halo = ds.halo(some_id)
>> my_halo["particle_mass"]
>>
>> 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.
>>
>> 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.
>>
>> Thanks!
>>
>> Britton
>>
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>>
>
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