[yt-dev] Halo Catalog unit error

[Nathan Goldbaum]

On Sun, Jun 12, 2016 at 6:47 PM, Rasmi Elasmar <re2300 at columbia.edu> wrote:

> Hi all,
>
> I'm running into more issues with Halo Catalogs and units. I'm not sure if
> the last PR <https://bitbucket.org/yt_analysis/yt/pull-requests/2208/> is
> causing this or not.
>

It might very well be.


> I'm running the latest code from the repo as of right now (fd8796c8e06d).
> Here's the error, generated on this data
> <https://drive.google.com/open?id=0BwK-7Z3S5X_yMDNyZ1RTcG56SFU> with this
> script <https://gist.github.com/rasmi/6cf6017b50277390735dd484c120855f>.
>

Thanks! If you don't spot the fix, I'll try to take a look at this tomorrow.


>
> /work/03330/tg826294/applications/pythonenv/lib/python2.7/site-packages/yt-3.3.dev0-py2.7-linux-x86_64.egg/yt/units/yt_array.py:976:
>> RuntimeWarning: divide by zero encountered in divide
>>   return super(YTArray, self).__div__(ro)
>> Traceback (most recent call last):
>>   File "/work/03330/tg826294/applications/scripts/findhalos.py", line 65,
>> in <module>
>>     hc.create()
>>   File
>> "/work/03330/tg826294/applications/pythonenv/lib/python2.7/site-packages/yt-3.3.dev0-py2.7-linux-x86_64.egg/yt/analysis_modules/halo_analysis/halo_catalog.py",
>> line 335, in create
>>     self._run(save_halos, save_catalog, njobs=njobs, dynamic=dynamic)
>>   File
>> "/work/03330/tg826294/applications/pythonenv/lib/python2.7/site-packages/yt-3.3.dev0-py2.7-linux-x86_64.egg/yt/utilities/parallel_tools/parallel_analysis_interface.py",
>> line 302, in barrierize
>>     return func(*args, **kwargs)
>>   File
>> "/work/03330/tg826294/applications/pythonenv/lib/python2.7/site-packages/yt-3.3.dev0-py2.7-linux-x86_64.egg/yt/analysis_modules/halo_analysis/halo_catalog.py",
>> line 427, in _run
>>     action(new_halo)
>>   File
>> "/work/03330/tg826294/applications/pythonenv/lib/python2.7/site-packages/yt-3.3.dev0-py2.7-linux-x86_64.egg/yt/analysis_modules/halo_analysis/halo_callbacks.py",
>> line 60, in __call__
>>     self.function(halo, *self.args, **self.kwargs)
>>   File
>> "/work/03330/tg826294/applications/pythonenv/lib/python2.7/site-packages/yt-3.3.dev0-py2.7-linux-x86_64.egg/yt/analysis_modules/halo_analysis/halo_callbacks.py",
>> line 571, in iterative_center_of_mass
>>     sphere = halo.halo_catalog.data_ds.sphere(center_orig,
>> halo.quantities[radius_field])
>>   File
>> "/work/03330/tg826294/applications/pythonenv/lib/python2.7/site-packages/yt-3.3.dev0-py2.7-linux-x86_64.egg/yt/data_objects/selection_data_containers.py",
>> line 649, in __init__
>>     if radius < self.index.get_smallest_dx():
>>   File
>> "/work/03330/tg826294/applications/pythonenv/lib/python2.7/site-packages/yt-3.3.dev0-py2.7-linux-x86_64.egg/yt/units/yt_array.py",
>> line 1095, in __lt__
>>     return super(YTArray, self).__lt__(oth)
>>   File
>> "/work/03330/tg826294/applications/pythonenv/lib/python2.7/site-packages/yt-3.3.dev0-py2.7-linux-x86_64.egg/yt/units/yt_array.py",
>> line 1225, in __array_wrap__
>>     raise YTUfuncUnitError(context[0], unit1, unit2)
>> yt.utilities.exceptions.YTUfuncUnitError: The NumPy <ufunc 'less'>
>> operation is only allowed on objects with identical units. Convert one of
>> the arrays to the other's units first. Received units (code_length) and
>> (code_length).
>
>
>
This means you're directly comparing units from two different datasets
(maybe the halo catalog dataset and the original dataset?). If these two
are identical, this should work, but maybe there's a bug in the handling
for that.

In fact, `validate_comparison_units` (see
https://bitbucket.org/yt_analysis/yt/src/fd8796c8e06dabb5deee71b1a40a6e7c37adc9b3/yt/units/yt_array.py?at=yt&fileviewer=file-view-default#yt_array.py-166)
is supposed to take care of this case - so I guess the bug is there? I
don't think users should hit this exception unless they're using a ufunc
directly. (i.e. np.less, not a < b).


> Has anyone run into this before? yt seems to think these two units aren't
> the same -- is it possible the HaloCatalog unit import is being done
> incorrectly? At this point, I haven't written anything to the disk, so I'm
> not sure what the issue might be.
>

Sorry for the trouble and thanks for the careful report. If you file an
issue to track this we can move further discussion there:

https://bitbucket.org/yt_analysis/yt/issues/new


>
>
> Thanks,
>
> Rasmi
>
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