Updated Python API MultiGroupXS.load_from_statepoint(...) to properly handle tally slicing of distribcell tallies

docs/source/pythonapi/examples/multi-group-cross-sections.rst

@@ -0,0 +1,11 @@
+====================================
+Multi-Group Cross Section Generation
+====================================
+
+.. only:: html
+
+    .. notebook:: multi-group-cross-sections.ipynb
+
+.. only:: latex
+
+    IPython notebooks must be viewed in the online HTML documentation.

docs/source/pythonapi/index.rst

@@ -65,6 +65,7 @@ on a given module or class.
     examples/post-processing
     examples/pandas-dataframes
     examples/tally-arithmetic
+    examples/multi-group-cross-sections
 
 .. _Jupyter: https://jupyter.org/
 .. _NumPy: http://www.numpy.org/

openmc/mgxs/mgxs.py

@@ -441,14 +441,24 @@ class MultiGroupXS(object):
         # Create Tallies to search for in StatePoint
         self.create_tallies()
 
+        # Use tally "slicing" to ensure that tallies correspond to our domain
+        # NOTE: This is important if tally merging was used
+        if self.domain_type != 'distribcell':
+            filters = [self.domain_type]
+            filter_bins = [(self.domain.id,)]
+        # Distribcell filters only accept single cell - neglect it when slicing
+        else:
+            filters = []
+            filter_bins = []
+
         # Find, slice and store Tallies from StatePoint
         # The tally slicing is needed if tally merging was used
         for tally_type, tally in self.tallies.items():
             sp_tally = statepoint.get_tally(tally.scores, tally.filters,
                                             tally.nuclides,
                                             estimator=tally.estimator)
-            sp_tally = sp_tally.get_slice(tally.scores, [self.domain_type],
-                                          [(self.domain.id,)], tally.nuclides)
+            sp_tally = sp_tally.get_slice(tally.scores, filters,
+                                          filter_bins, tally.nuclides)
             self.tallies[tally_type] = sp_tally
 
     def get_xs(self, groups='all', subdomains='all', nuclides='all',

openmc/tallies.py

@@ -2366,7 +2366,8 @@ class Tally(object):
                     if filter_type in ['energy', 'energyout']:
                         bin_indices.extend([bin_index, bin_index+1])
                     elif filter_type == 'distribcell':
-                        bin_indices.append(0)
+                        indices = [(bin,) for bin in range(filter.num_bins)]
+                        bin_indices.extend(indices)
                     else:
                         bin_indices.append(bin_index)