[yt-dev] New default particle union?

[Michael Zingale]

I think the name n-body only makes sense for datasets with active
particles, not those with passive particles.  The latter are the ones that
I typically deal with.  So maybe a different name?  or maybe a way for a
code to register if it is using active or passive particles?

On Wed, Mar 29, 2017 at 5:36 PM, Nathan Goldbaum <nathan12343 at gmail.com>
wrote:

>
>
> On Wed, Mar 29, 2017 at 4:33 PM, Cameron Hummels <chummels at gmail.com>
> wrote:
>
>> Wait, so we'd have both an 'all' ftype and an 'n-body' ftype and the
>> 'n-body' ftype would just include non-gas particles (ie ones without the
>> 'smoothing_length' field)?  I'm assuming this won't add more computational
>> load when reading in the dataset?
>>
>
> I doubt it. There will just be some more fields in ds.derived_field_list
> (one 'n-body' field for each of the 'all' fields).
>
>
>> If that's the case, then I'm +0.5 on it.  I haven't had a need for it up
>> to this point, but maybe other people really need it?
>>
>> On Wed, Mar 29, 2017 at 2:21 PM, John ZuHone <jzuhone at gmail.com> wrote:
>>
>>> +1.
>>>
>>> "n_body"?
>>>
>>> On Mar 29, 2017, at 5:19 PM, Matthew Turk <matthewturk at gmail.com> wrote:
>>>
>>> +1, and I think updating YTEP-0031 is sufficient.  Not sure that
>>> "n-body" specifically is my preference, since it's not tokenizable, but
>>> maybe it's fine.
>>>
>>> On Wed, Mar 29, 2017 at 4:18 PM, Nathan Goldbaum <nathan12343 at gmail.com>
>>> wrote:
>>>
>>>> Hi all,
>>>>
>>>> I'd like to propose adding a new particle union that should be defined
>>>> for all datasets that include particles. This came up in the context of the
>>>> demeshening work (see https://bitbucket.org/yt_
>>>> analysis/ytep/pull-requests/67 for more details).
>>>>
>>>> Right now many of the derived quantities make a distinction between
>>>> calculating results using just the gas or just the particles or both. Up
>>>> until now they have calculated the results for particles using particle
>>>> fields from the 'all' particle union. This makes perfect sense for AMR data
>>>> but doesn't really make sense for SPH data, since it will double-count SPH
>>>> particles. In fact, I think this is an issue even without the demeshening,
>>>> but the demeshening makes it more starkly apparent.
>>>>
>>>> I'd like to propose defining a new "n-body" particle union (suggestions
>>>> for alternate names are very welcome) that will be defined for all yt
>>>> datasets. This union will be identical to the 'all' particle union for AMR
>>>> data and N-body particle data, but for SPH data will only include the
>>>> particle types that aren't SPH particles (if any). That means the "n-body"
>>>> particle type represents infinitesimal particles but not particles that
>>>> have finite extents (e.g. an SPH particle's smoothing region).
>>>>
>>>> I think this new particle type would probably be generically useful
>>>> beyond just the derived quantities, maybe even more useful than "all". I
>>>> also kind of prefer the name "n-body" to "all" since it more prominently
>>>> indicates that it's associated with particle data.
>>>>
>>>> Please let me know if you have thoughts or suggestions about this
>>>> proposal. I'm happy to draft a YTEP or update YTEP-0031 with more details
>>>> if people want to see that.
>>>>
>>>> -Nathan
>>>>
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>>>>
>>>>
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>>
>>
>> --
>> Cameron Hummels
>> NSF Postdoctoral Fellow
>> Department of Astronomy
>> California Institute of Technology
>> http://chummels.org
>>
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>>
>
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-- 
Michael Zingale
Associate Professor

Dept. of Physics & Astronomy • Stony Brook University • Stony Brook, NY
11794-3800
*phone*:  631-632-8225
*e-mail*: Michael.Zingale at stonybrook.edu
*web*: http://www.astro.sunysb.edu/mzingale
github: http://github.com/zingale
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