New issue 1220: sz_kinetic field fails on FLASH datasets for certain axes https://bitbucket.org/yt_analysis/yt/issues/1220/sz_kinetic-field-fails-on-f...

John ZuHone:

The following simple script fails mysteriously when projecting `"sz_kinetic"` along either the y or z-axis, but not the x-axis:

```python import yt ds = yt.load("GasSloshing/sloshing_nomag2_hdf5_plt_cnt_0100") prj = ds.proj("sz_kinetic", 2) ```

```pycon --------------------------------------------------------------------------- RuntimeError Traceback (most recent call last) <ipython-input-3-fec24ac2f48f> in <module>() ----> 1 prj = ds.proj("sz_kinetic", 2)

/Users/jzuhone/Source/yt/yt/data_objects/construction_data_containers.py in __init__(self, field, axis, weight_field, center, ds, data_source, style, method, field_parameters, max_level) 260 261 if not self.deserialize(field): --> 262 self.get_data(field) 263 self.serialize() 264

/Users/jzuhone/Source/yt/yt/data_objects/construction_data_containers.py in get_data(self, fields) 334 self._initialize_projected_units(fields, chunk) 335 _units_initialized = True --> 336 self._handle_chunk(chunk, fields, tree) 337 # Note that this will briefly double RAM usage 338 if self.method == "mip":

/Users/jzuhone/miniconda3/lib/python3.5/contextlib.py in __exit__(self, type, value, traceback) 75 value = type() 76 try: ---> 77 self.gen.throw(type, value, traceback) 78 raise RuntimeError("generator didn't stop after throw()") 79 except StopIteration as exc:

/Users/jzuhone/Source/yt/yt/data_objects/data_containers.py in _field_parameter_state(self, field_parameters) 953 new_field_parameters.update(old_field_parameters) 954 self.field_parameters = new_field_parameters --> 955 yield 956 self.field_parameters = old_field_parameters 957

/Users/jzuhone/Source/yt/yt/data_objects/construction_data_containers.py in get_data(self, fields) 334 self._initialize_projected_units(fields, chunk) 335 _units_initialized = True --> 336 self._handle_chunk(chunk, fields, tree) 337 # Note that this will briefly double RAM usage 338 if self.method == "mip":

/Users/jzuhone/Source/yt/yt/data_objects/construction_data_containers.py in _handle_chunk(self, chunk, fields, tree) 434 v = np.empty((chunk.ires.size, len(fields)), dtype="float64") 435 for i, field in enumerate(fields): --> 436 d = chunk[field] * dl 437 v[:,i] = d 438 if self.weight_field is not None:

/Users/jzuhone/Source/yt/yt/data_objects/data_containers.py in __getitem__(self, key) 268 return self.field_data[f] 269 else: --> 270 self.get_data(f) 271 # fi.units is the unit expression string. We depend on the registry 272 # hanging off the dataset to define this unit object.

/Users/jzuhone/Source/yt/yt/data_objects/data_containers.py in get_data(self, fields) 1182 1183 fields_to_generate += gen_fluids + gen_particles -> 1184 self._generate_fields(fields_to_generate) 1185 for field in list(self.field_data.keys()): 1186 if field not in ofields:

/Users/jzuhone/Source/yt/yt/data_objects/data_containers.py in _generate_fields(self, fields_to_generate) 1240 for f in gip.fields: 1241 if f not in fields_to_generate: -> 1242 fields_to_generate.append(f) 1243 1244 @contextmanager

/Users/jzuhone/miniconda3/lib/python3.5/contextlib.py in __exit__(self, type, value, traceback) 75 value = type() 76 try: ---> 77 self.gen.throw(type, value, traceback) 78 raise RuntimeError("generator didn't stop after throw()") 79 except StopIteration as exc:

/Users/jzuhone/Source/yt/yt/data_objects/data_containers.py in _field_lock(self) 1245 def _field_lock(self): 1246 self._locked = True -> 1247 yield 1248 self._locked = False 1249

/Users/jzuhone/Source/yt/yt/data_objects/data_containers.py in _generate_fields(self, fields_to_generate) 1202 fi = self.ds._get_field_info(*field) 1203 try: -> 1204 fd = self._generate_field(field) 1205 if fd is None: 1206 raise RuntimeError

/Users/jzuhone/Source/yt/yt/data_objects/data_containers.py in _generate_field(self, field) 308 if tr is None: 309 raise YTCouldNotGenerateField(field, self.ds) --> 310 return tr 311 312 def _generate_fluid_field(self, field):

/Users/jzuhone/miniconda3/lib/python3.5/contextlib.py in __exit__(self, type, value, traceback) 75 value = type() 76 try: ---> 77 self.gen.throw(type, value, traceback) 78 raise RuntimeError("generator didn't stop after throw()") 79 except StopIteration as exc:

/Users/jzuhone/Source/yt/yt/data_objects/data_containers.py in _field_type_state(self, ftype, finfo, obj) 965 else: 966 obj._current_fluid_type = ftype --> 967 yield 968 obj._current_particle_type = old_particle_type 969 obj._current_fluid_type = old_fluid_type

/Users/jzuhone/Source/yt/yt/data_objects/data_containers.py in _generate_field(self, field) 305 tr = self._generate_particle_field(field) 306 else: --> 307 tr = self._generate_fluid_field(field) 308 if tr is None: 309 raise YTCouldNotGenerateField(field, self.ds)

/Users/jzuhone/Source/yt/yt/data_objects/data_containers.py in _generate_fluid_field(self, field) 325 rv = self._generate_spatial_fluid(field, ngt_exception.ghost_zones) 326 else: --> 327 rv = finfo(gen_obj) 328 return rv 329

/Users/jzuhone/Source/yt/yt/fields/derived_field.py in __call__(self, data) 193 raise RuntimeError( 194 "Something has gone terribly wrong, _function is NullFunc " + --> 195 "for %s" % (self.name,)) 196 with self.unit_registry(data): 197 dd = self._function(self, data)

RuntimeError: Something has gone terribly wrong, _function is NullFunc for ('flash', 'velz') ```

Responsible: jzuhone