Some advice on an unusual field case
Hi folks, I’d like to get some feedback from you all on a new yt development issue I’ve run into. So Arepo has passive tracer particles. The way these are handled is that in the snapshot file the tracer particle IDs are stored and the gas Voronoi cell IDs that they are matched to are stored. So if you want any quantity, including position, velocity, density, etc, of the tracer, you’d want to map them from the gas cell ID. So we need a mapping from PartType0 to PartType3. This seems complicated for a couple of reasons: 1. Since we do things in chunks, how would we get chunks that have the particles of both types that you’d want in the same chunk? Or would this be two chunks at once? 2. Ideally you’d just want to be able to map every gas field to a tracer field, even derived gas fields like angular momentum and entropy, etc. This does not seem like a trivial thing. Does anyone have any thoughts here? I think this is kind of a new type of issue for us. Best, John
Hi John,
Just so I am completely sure I understand, are we operating on the
assumption that the tracer particles will *not* be in the same *file* (not
necessarily chunk) as the gas particles they're assigned to?
On Wed, Aug 26, 2020 at 10:46 AM John ZuHone
Hi folks,
I’d like to get some feedback from you all on a new yt development issue I’ve run into.
So Arepo has passive tracer particles. The way these are handled is that in the snapshot file the tracer particle IDs are stored and the gas Voronoi cell IDs that they are matched to are stored. So if you want any quantity, including position, velocity, density, etc, of the tracer, you’d want to map them from the gas cell ID.
So we need a mapping from PartType0 to PartType3. This seems complicated for a couple of reasons:
1. Since we do things in chunks, how would we get chunks that have the particles of both types that you’d want in the same chunk? Or would this be two chunks at once? 2. Ideally you’d just want to be able to map every gas field to a tracer field, even derived gas fields like angular momentum and entropy, etc. This does not seem like a trivial thing.
Does anyone have any thoughts here? I think this is kind of a new type of issue for us.
Best,
John _______________________________________________ yt-dev mailing list -- yt-dev@python.org To unsubscribe send an email to yt-dev-leave@python.org https://mail.python.org/mailman3/lists/yt-dev.python.org/ Member address: matthewturk@gmail.com
Hi Matt,
On Aug 26, 2020, at 11:48 AM, Matthew Turk
wrote: Just so I am completely sure I understand, are we operating on the assumption that the tracer particles will *not* be in the same *file* (not necessarily chunk) as the gas particles they're assigned to?
Hmm, good question. I do not know how this works in terms of multiple files (I always just dump one file per snapshot). But maybe let’s assume they are in the same file.
Ok, in *that* case, I think we might be able to mock up a way of reading a
given file at a time in total for one particle type, then iterating for the
other particle type.
The other option that immediately comes to mind, which isn't precisely
ideal, would be to do a dual iteration over chunks using cloned data
sources. I'm sure there is a better way but it's not immediately coming to
me.
Although, maybe this would be a good match for the particle_operation
function in octree_subset. In principle the gas particles should be the
nearest neighbors to the tracer particles, right?
On Wed, Aug 26, 2020 at 10:51 AM John ZuHone
Hi Matt,
On Aug 26, 2020, at 11:48 AM, Matthew Turk
wrote: Just so I am completely sure I understand, are we operating on the assumption that the tracer particles will *not* be in the same *file* (not necessarily chunk) as the gas particles they're assigned to?
Hmm, good question. I do not know how this works in terms of multiple files (I always just dump one file per snapshot). But maybe let’s assume they are in the same file.
_______________________________________________ yt-dev mailing list -- yt-dev@python.org To unsubscribe send an email to yt-dev-leave@python.org https://mail.python.org/mailman3/lists/yt-dev.python.org/ Member address: matthewturk@gmail.com
participants (2)
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John ZuHone
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Matthew Turk