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

[Hsi-Yu Schive]

Hi Matt,

Thanks for the explanation! Now it's clearer to me.

Let me describe what I understand so far, and please correct me if there is anything wrong.

When I use "add_gamer_field" to add a build-in field in GAMER,
in principle I DON'T need to set the "function" parameter since the field values can
be set directly to the loaded values, but I DO need to provide the "convert_function"
parameter to properly convert unit to cgs. 

On the other hand, when I use "add_field" to define a derived field, I DO need to set 
the "function" parameter to describe how to get the new derived field from the 
existing fields, but in principle I DON'T need to provide the "convert_function" again
since all existing fields are already in cgs units. Is that correct?

One more question. In the field.py file of flash, I saw the following lines.

   def _get_convert(fname):
       def _conv(data):
           return data.convert(fname)
    return _conv

    add_flash_field("divb", function=NullFunc, take_log=False,
                               convert_function=_get_convert("divb"),
                                units = r"\mathrm{Gau\ss}\/\rm{cm}")

My question is:
1. Where can I explicitly set the operations performed by data.convert("divb")?

2. What "field" variables can be put into data["field"] (may all the fields
that have been added by add_field and gamer_add_field)?


Thank you very much for the help. The YT group is so active and I
will be more than willing to have GAMER supported in YT ASAP !!

Sincerely,
Hsi-Yu



  ----- Original Message ----- 
  From: Matthew Turk 
  To: yt-dev at lists.spacepope.org 
  Sent: Monday, October 29, 2012 10:42 PM
  Subject: Re: [yt-dev] Question: adding new fields for GAMER


  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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