[yt-dev] Question: adding new fields for GAMER

[Matthew Turk]

Hi Hsi-Yu,

On Mon, Oct 29, 2012 at 9:54 AM, Hsi-Yu Schive <hyschive at ntu.edu.tw> wrote:
> Dear all,
>
> I'm trying to add new fields used in GAMER by editing the file "field.py",
> but I'm confused about the following declarations.
>
>    KnownGAMERFields = FieldInfoContainer()
>    add_gamer_field = KnownGAMERFields.add_field
>
>    GAMERFieldInfo = FieldInfoContainer.create_with_fallback(FieldInfo)
>    add_field = GAMERFieldInfo.add_field
>
> What is the difference between "KnownGAMERField" and "GAMERFieldInfo"?
> To me, it seems that they are both instantiations of the class
> FieldInfoContainer,
> except that GAMERFieldInfo has a fallback function "FieldInfo".
> Similarly, what's the difference between "add_gamer_field" and "add_field"?

Ah, this is something that should be made a bit clearer in the
documentation.  The distinction is somewhat subtle, and relies on
whether a field is something that could reasonably be expected to
exist in a file, or

A "known" field would be one that can exist in an output file.  The
others are fields that could be derived from output from the
particular code.  It's a bit of a semantic difference, but it helps
with how derived fields are detected.  So if you know a field is going
to (potentially) exist inside a data dump, it gets added with
add_gamer_field.  As an example, FLASH has the field "dens".  We want
to be able to access this field with either "dens" or "Density", so we
do:

add_flash_field("dens", function=NullFunc, ...)

and then we add a translation (i.e., a *flash-specific* derived field) with:

add_field("Density", function=TranslationFunc("dens"))

I hope that helps!

Also, thanks for adding support for GAMER!

-Matt

>
> Thanks in advance for the help!!
>
> Sincerely,
> Hsi-Yu
>
>
>
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