[Yt-dev] Particles

[Matthew Turk]

Hi guys,

Thanks for the feedback.  I think we'll go with the example y'all
liked.  I think we can get going on this in a couple weeks or a month
at the outside, but it should be made a priority.  I also agree, this
should not be exclusive for dataspace access, but instead that should
just be the most optimized way of accessing the data.

Thanks!

-Matt

PS I've stuck up a new front page at yt.enzotools.org.  If anybody has
any images for the gallery, send them my way...

On Thu, Sep 10, 2009 at 4:27 AM, John Wise <john.h.wise at nasa.gov> wrote:
> Hi,
> I like the first example the best because usually the user has some idea of
> the volume they're interested in, such as looking for stars or tracer
> particles in a particular halo or searching for all of the stars in the
> simulation.
> The dataspace framework is pretty cool because it removes the intensive need
> of searching through the *entire* particle list for only (in most cases) a
> handful of particles.  Of course because this feature is new, we'd still
> have to support searching for certain particles if the dataspace doesn't
> exist.
> Cheers,
> John
> On 10 Sep 2009, at 00:11, Britton Smith wrote:
>
> I think something like the first example you gave would be the best.  It's
> definitely more in keeping with the data_object[field] notation for getting
> grid data.  In a very similar vein, I find it much more intuitive to think
> of asking for the particles or grid data associated with a particular object
> than say start with some larger structure for handling particles for the
> entire pf, and give me only the ones in some sphere or other object (this is
> my interpretation of the second example you gave).
>
> Additionally, I think particle data-space stuff you done in Enzo is great.
> It seems silly to have to read in an entire set of particles only to filter
> most of them back out, like with star particles.  This will also come in
> handy for other people who are working with tracer particles.
>
> Britton
>
> On Wed, Sep 9, 2009 at 8:47 PM, Matthew Turk <matthewturk at gmail.com> wrote:
>>
>> Hi guys,
>>
>> I've noticed several of you making commits about particles.  (John,
>> Britton, looking at you guys.)  In recent versions of Enzo, I stuck in
>> a dataspace supplement that pre-computes dataspaces for different
>> particle types in each grid, which should makes things really cheap to
>> read *only* star particles, or particles of a different type.  I've
>> put in support for this in the yt-hg repo, but the biggest problem
>> with it was that I couldn't figure out the right way to address it --
>> so I'd like to put out there a question to you guys.
>>
>> In an ideal world, if you have some data object:
>>
>> data_obj
>>
>> what is the best way to be able to address particles of different
>> types, and only get those particles?  (Let's pretend either that IO is
>> cheap, or we have the dataspace hack.)
>>
>> For instance,
>>
>> data_object.particles[type]["x"] # for instance
>>
>> or maybe,
>>
>> pf.h.particles[type].sphere(...)
>>
>> or something?  What do you think?  Any off-the-wall ideas?
>>
>> -Matt
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