[yt-dev] Field Parameters Bug

Nathan Goldbaum nathan12343 at gmail.com
Wed Oct 1 13:26:43 PDT 2014


On Wed, Oct 1, 2014 at 1:25 PM, Nathan Goldbaum <nathan12343 at gmail.com>
wrote:

>
>
> On Wed, Oct 1, 2014 at 1:22 PM, Hilary Egan <hilaryye at gmail.com> wrote:
>
>> Hi all,
>>
>> I've encountered a bug with this example
>> <http://yt-project.org/doc/developing/creating_derived_fields.html#a-more-complicated-example> in
>> the docs of getting/setting field parameters of a dataset for use in a
>> derived field. The example works fine for known yt field parameters like
>> bulk_velocity, but if you change every instance of "bulk_velocity" to
>> "my_bulk_velocity" (sample script
>> <http://paste.yt-project.org/show/5142/>), then it breaks with this error
>> <http://paste.yt-project.org/show/5140/>.
>>
>> It seems as though this breaks because `has_field_parameter` always
>> returns True
>>
>
> Note that this is specifically has_field_parameter as defined in the
> field_detector class:
>
>
> https://bitbucket.org/yt_analysis/yt/src/05de9b2f84be6cc8b933f0af75ac211a57a44d7d/yt/fields/field_detector.py?at=yt#cl-215
>
>
>> , and there is no way to know ahead of time what units a user-defined
>> field parameter will take, so the mock field data can't be set up
>> correctly. Nathan suggested via IRC that this might necessitate creating a
>> way to register user-defined field parameters, but it's probably worth
>> brain-storming about if anyone else has any other suggestions!
>>
>
> The main issue with the way field parameters work right now is that we
> can't know the units ahead of time for user-defined field parameters. We
> could either have a field parameter registry where users would encode that
> before loading their data, or we could temporarily disable the unit system
> during field detection, which I am loathe to do since it will cause bugs.
>

I meant to say "mask bugs" here.


>
>
>>
>> -Hilary
>>
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>>
>>
>
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