[yt-dev] Issue #909: calculate_isocontour_flux function raises error in parallel analysis interface (yt_analysis/yt)

[Nathan Goldbaum]

New issue 909: calculate_isocontour_flux function raises error in parallel analysis interface
https://bitbucket.org/yt_analysis/yt/issue/909/calculate_isocontour_flux-function-raises

Nathan Goldbaum:

The following test script:

```
import yt
ds = yt.load('IsolatedGalaxy/galaxy0030/galaxy0030')
dd = ds.all_data()
dd.calculate_isocontour_flux('density', 1e-23, 'x-velocity', 'y-velocity', 'z-velocity', 'density')
```

raises the following error:


```
#!python

AttributeError                            Traceback (most recent call last)
/home/goldbaum/Documents/yt-hg/yt/mods.pyc in <module>()
----> 1 dd.calculate_isocontour_flux('density', 1e-23, 'x-velocity', 'y-velocity', 'z-velocity', 'density')

/home/goldbaum/Documents/yt-hg/yt/data_objects/data_containers.pyc in calculate_isocontour_flux(self, field, value, field_x, field_y, field_z, fluxing_field)
   1106         """
   1107         flux = 0.0
-> 1108         for g in self._get_grid_objs():
   1109             flux += self._calculate_flux_in_grid(g, field, value,
   1110                     field_x, field_y, field_z, fluxing_field)

/home/goldbaum/Documents/yt-hg/yt/utilities/parallel_tools/parallel_analysis_interface.pyc in _get_grid_objs(self)
   1065         if self._distributed:
   1066             return ParallelObjectIterator(self, True, attr='_grids')
-> 1067         return ObjectIterator(self, True, attr='_grids')
   1068 
   1069     def get_dependencies(self, fields):

/home/goldbaum/Documents/yt-hg/yt/utilities/parallel_tools/parallel_analysis_interface.pyc in __init__(self, pobj, just_list, attr)
    146             gs = getattr(pobj, attr)
    147         else:
--> 148             gs = getattr(pobj._data_source, attr)
    149         if len(gs) == 0:
    150             raise YTNoDataInObjectError(pobj)

AttributeError: 'YTRegion' object has no attribute '_data_source'
```

I think the parallel analysis interface should be using the chunking system here, but I'm not sure.  I also a little mystified why the unit tests for this function didn't pick this up.


Responsible: MatthewTurk