[yt-dev] GDF PR--call for some feedback

Cameron Hummels chummels at gmail.com
Sat Jul 12 12:06:39 PDT 2014


Hi John,

I'm not averse to the changes in the GDF standard you propose.  I think now
that yt-3.0 is incorporating units as cleanly as it is, this makes sense to
allow the format to specify an arbitary unittype instead of requiring cgs,
since it can be so easily modified within current/future versions of yt.

I honestly don't know how many people are using GDF, but it seems like
these changes would break backwards-compatibility.  Is it possible for us
to retain that compatibility by automatically running "field_to_cgs" on GDF
files which do not possess the HDF5 attributes specifying the units?  Or
perhaps since yt is the main source of GDF files, we can just move forward
without having to worry about too much backwards-compatibility issues?

Anyway, this seems like a positive change. +1 to continue on this.

Cameron


On Sat, Jul 12, 2014 at 11:48 AM, John Zuhone <jzuhone at gmail.com> wrote:

> Hi all,
>
> I have a work-in-progress PR in the hopper regarding GDF reading and
> writing:
>
>
> https://bitbucket.org/yt_analysis/yt/pull-request/1001/wip-some-gdf-writing-work/diff
>
> What it does is implement direct writing of covering grids to GDF
> files (something I've been using in my research, to work with the
> resulting files directly in yt) and clobbering existing files with the
> same path if the user allows for it.
>
> However, when fiddling around with this I determined that it was
> necessary to make GDF more unit-aware. Ultimately, I determined that
> changes were needed that would break the standard that we had
> determined for the files (http://yt-project.org/gdf.txt).
>
> The two main changes are:
>
> 1) Remove "field_to_cgs", and allow the fields to be in whatever units
> we wish them to be in the file (which are specified as HDF5
> attributes).
>
> 2) Add a new top-level group containing the information for
> "length","mass", and "time" units. These will be used when the file is
> opened up in yt to determine the units.
>
> Since (for now) we do automatic conversion to cgs, that is something
> that is still left unimplemented, but otherwise I think this is all to
> do for now.
>
> I'm writing the email in case anyone has any suggestions or objections
> to the format changes--particularly Jeff or Kacper. We'll obviously
> need to document them if they are accepted.
>
> Best,
>
> John
>
> --
> John ZuHone
>
> Postdoctoral Researcher
> NASA/Goddard Space Flight Center
>
> jzuhone at gmail.com
> john.zuhone at nasa.gov
> _______________________________________________
> yt-dev mailing list
> yt-dev at lists.spacepope.org
> http://lists.spacepope.org/listinfo.cgi/yt-dev-spacepope.org
>



-- 
Cameron Hummels
Postdoctoral Researcher
Steward Observatory
University of Arizona
http://chummels.org
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