[yt-dev] yt Particle Plots & openPMD Frontend

[Fabian Koller]

Wow!

Thanks for the speedy and thorough solution. It seems to work
flawlessly, based on a quick test.

I can see that the decision to produce known fields on the fly seems a
bit odd, but there's a simple reason behind it: The openPMD stadard (in
theory) allows for infinitely many different fields to exist, all of
them with different unit-dimensions. Very little is actually static:
only the basic structure of our data, not its content, not its names,
not its units and dimensions. Trying to cover as much of the standard as
is feasible, we decided to dynamically generate known fields. (Also,
having done it this way has helped me internalize the standard. A lot.)

If you're interested our reasoning more than this brief explanation, I'd
refer you to the current (well, upcoming) written standard:
https://github.com/openPMD/openPMD-standard/blob/upcoming-1.0.1/STANDARD.md,
in particular "unitDimension".


--Fabian

On 10/06/16 17:55, Nathan Goldbaum wrote:
> Hey,
>
> The issue you're having is because you're constructing
> known_other_fields dynamically. All the other frontends define it
> statically, so it's filled out by the time it's needed in the
> `setup_fluid_aliases` function defined in in
> yt/fields/field_info_container.py. The fix is to change the order of
> operations - setup known_other_fields and known_particle_fields before
> calling the __init__ method on the superclass of OpenPMDFieldInfo.
>
> You're also incorrectly setting the units of the field to a Unit
> object --- the unit entry in the known_other_fields tuple should be a
> string.
>
> The following diff allows me to set the units properly for your frontend:
>
> http://paste.yt-project.org/show/6606/
>
> Out of curiosity - why build the known_other_fields and
> known_particle_fields tuples dynamically? The reason they're static
> for all the other frotends is to make it easy to reason about which
> fields are associated with a given frontend and so that the fields
> known by a given frontend are independent of any particular dataset
> you might be looking at.
>
> By the way, it also looks like the 'all' particle union is working
> correctly - are you still having issues with that?
>
> -Nathan
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