[yt-dev] Particle Deposition fields and grid boundaries

Nathan Goldbaum nathan12343 at gmail.com
Tue Oct 7 20:40:14 PDT 2014


On Tue, Oct 7, 2014 at 7:45 PM, Matthew Turk <matthewturk at gmail.com> wrote:

> On Tue, Oct 7, 2014 at 7:55 PM, Andrew Myers <atmyers2 at gmail.com> wrote:
> > Hi Folks,
> >
> > I'm trying to understand how the particle deposition fields work for
> > grid-based codes. Specifically, how does yt handle particles that are
> close
> > to the grid boundaries, so that the CIC interpolation stencil involves
> cells
> > on grid(s) other than the one that contains the particle position?. Like,
> > say I did:
> >
> > import yt
> > ds = yt.load(fn)
> > g = ds.index.grids[0]
> > print g['deposit', 'all_cic']
> >
> > How does yt handle the fact that particles other than those living on "g"
> > can contribute to the total CIC density? Does it grab a layer of "ghost
> > particles" somehow? I can't seem to find where that happens.
> >
> > Sorry if I'm just missing something obvious here...
>

Andrew's original e-mail prompted me to make the following notebook, which
might prove useful for constructing a unit test:

http://nbviewer.ipython.org/gist/ngoldbaum/eb40dfe74cd58a4e16ba


>
> It doesn't, and you're not.  This is something it should do, but does
> not currently.  If you're using a "smoothing" operation, it will, as
> then it handles non-local particles, but deposit operations don't do
> ghost zones.
>

Smoothing is also only implemented for octrees.


>
> This is something we should fix, and that we probably could by simply
> making all the CIC fields ValidateSpatial(1).  Can you give that a
> shot?
>

Will this have interactions with https://trello.com/c/SFuSSoIo ?

I think the answer is no, since we're querying particle fields and
selection doesn't require cascading interpolation, but I just want to
double-check.


> >
> > Best,
> > Andrew
> >
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> > http://lists.spacepope.org/listinfo.cgi/yt-dev-spacepope.org
> >
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