[yt-dev] Field units from code to code

[Casey W. Stark]

Hi Nathan.

I'm also worried about this and I agree that fields with the same name
should all be consistent. I would support some sort of cleanup of frontend
fields, and I can get the Nyx fields in line and help with Enzo.

I doubt we can do this, but I would prefer changing the field names as part
of the removing enzo-isms and geometry handling refactoring pushes. For
instance, the field in Orion could be thermal_energy_density and the field
in Enzo could be specific_thermal_energy. I also noticed this issue when I
was using "Density" in Enzo (proper density in cgs) and "density" in Nyx
(comoving density in cgs).

Best,
Casey


On Wed, Mar 28, 2012 at 1:47 PM, Nathan Goldbaum <goldbaum at ucolick.org>wrote:

> Hi all,
>
> On IRC today we noticed that Orion defines its ThermalEnergy field per
> unit volume but Enzo and FLASH define ThermalEnergy per unit mass.  Is this
> a problem?  Since yt defaults to the Enzo field names, should we try to
> make sure that all fields are defined using the same units as in Enzo?  Is
> there a convention for how different codes should define derived fields
> that are aliased to Enzo fields?
>
> One problem for this particular example is that the Pressure field is
> defined in terms of ThermalEnergy in universal_fields.py so the units of
> ThermalEnergy become important if a user merely wants the gas pressure in
> the simulation.
>
> One possible solution for this issue would be the units overhaul we're
> planning. If all fields are associated with a unit object, we can simply
> query the units to ensure that units are taken care of correctly and
> code-to-code comparisons aren't sensitive to the units chosen for fields in
> the frontend.
>
> Personally, I think it would be best if we could make sure that all of the
> fields aliased to Enzo fields have the same units.
>
> Nathan Goldbaum
> Graduate Student
> Astronomy & Astrophysics, UCSC
> goldbaum at ucolick.org
> http://www.ucolick.org/~goldbaum
>
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