[yt-users] Potential problem with the field_parameters dictionary in SlicePlot (and certainly others)

Wed Sep 3 12:09:12 PDT 2014

Hi Matt,

yt version 3.0.1 indeed solved this issue for me, that’s great thank you very much!

Antoine

Antoine STRUGAREK
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strugarek at astro.umontreal.ca
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antoine.strugarek at cea.fr
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Le 2014-09-03 à 14:41 , Matthew Turk <matthewturk at gmail.com> a écrit :

> Hi Antoine,
> 
> This should be fixed in the release put up last night, 3.0.1.  Britton
> Smith tracked this down and fixed it.  Apologies for the issue.
> 
> -Matt
> 
> On Wed, Sep 3, 2014 at 1:40 PM, Antoine Strugarek
> <strugarek at astro.umontreal.ca> wrote:
>> Thank for your answers, it confirms what I understood.
>> 
>> After digging a bit deeper in the Python and Cython codes, I think I may
>> have found another bug that adds up to the problem with ‘_set_center' I was
>> mentioning before. In ‘geometric_fields.py’, when computing the geometric
>> fields (take _cylindrical_r for instance, but it true for other fields as
>> well), the center from the field_parameters dictionary is subtracted from
>> the coords. Though, it appears that the coords are obtained from the
>> obtain_rvec function defined in geometry_utils.pyx, and in there the center
>> (from the field_parameters dictionary as well) is already subtracted. The
>> center is hence subtracted twice, which leads to weird behaviours when using
>> those geometrical fields. Please advise on what would be the best way to
>> cope with this issue, in order to use the already defined geometrical fields
>> (cylindrical and spherical).
>> 
>> Antoine
>> 
>> 
>> Le 2014-09-03 à 13:07 , Nathan Goldbaum <nathan12343 at gmail.com> a écrit :
>> 
>> 
>> 
>> On Wed, Sep 3, 2014 at 10:05 AM, Chris Malone <chris.m.malone at gmail.com>
>> wrote:
>>> 
>>> Hi Antoine,
>>> 
>>> As you hinted, the field_parameters dictionary is mainly used for derived
>>> fields and defaults to the center of the domain.  For a SlicePlot (and
>>> others), the keyword variable 'center' is actually what determines where in
>>> the domain the slice should be taken - it is completely independent of the
>>> field_parameters['center'] value.
>> 
>> 
>> You can also adjust the plot center using the set_center function that hangs
>> off of SlicePlot instances.
>> 
>>> 
>>> 
>>> Hope that helps.
>>> 
>>> Chris
>>> 
>>> 
>>> On Wed, Sep 3, 2014 at 10:45 AM, Antoine Strugarek
>>> <strugarek at astro.umontreal.ca> wrote:
>>>> 
>>>> Hi Matthew,
>>>> 
>>>> Thank you for the quick answer. I’m on 3.0 (obtained with
>>>> yt.__version__).
>>>> 
>>>> I’m not completely sure how to fix this since I’m discovering the code,
>>>> but I’m suspecting something strange there. To my understanding, the
>>>> field_parameters dictionary given in argument to SlicePlot should be used
>>>> for derived fields only, and the center keyword to specify the location
>>>> where the Slice should be taken, right?
>>>> Also, if I specify in advance the center (doing ad = ds.all_data() ;
>>>> ad.set_field_parameter("center", custom_center)), this new center does not
>>>> seem to be used in the SlicePlot to compute, e.g., the cylindrical radius
>>>> (in this latter case I try to do a SlicePlot without giving a
>>>> field_parameters dictionary in argument).
>>>> 
>>>> Antoine
>>>> 
>>>> 
>>>> Le 2014-09-03 à 12:27 , Matthew Turk <matthewturk at gmail.com> a écrit :
>>>> 
>>>>> Hi Antoine,
>>>>> 
>>>>> Thanks for reporting this!  Which version of the code are you on?  "yt
>>>>> instinfo" should be able to tell you this.
>>>>> 
>>>>> -Matt
>>>>> 
>>>>> On Wed, Sep 3, 2014 at 11:08 AM, Antoine Strugarek
>>>>> <strugarek at astro.umontreal.ca> wrote:
>>>>>> Hi,
>>>>>> 
>>>>>> I’ve been trying to specify by hand the ‘center’ entry of the
>>>>>> dictionary field_parameters to a SlicePlot so that the derived field can
>>>>>> make use of another center to compute, e.g., cylindrical coordinates. After
>>>>>> tracking why my specified center had no effect, I noticed that the function
>>>>>> _set_center is called when a SlicePlot is created, and this function erases
>>>>>> any ‘center’ entry in the field_parameters dictionary, putting there the
>>>>>> ‘center’ keyword specified as an argument to SlicePlot. It appears to me
>>>>>> this should not be the normal behaviour, but I may be misunderstanding
>>>>>> something. I would naively suggest not to update the ‘field_parameters’
>>>>>> dictionary in the _set_center function, though I’m not completely sure?
>>>>>> 
>>>>>> Thanks in advance for your help and suggestion about this issue!
>>>>>> 
>>>>>> Antoine
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