switch universe deepcopying for a fresh instance on clones

openmc/universe.py

@@ -1,7 +1,6 @@
 from abc import ABC, abstractmethod
 from collections import OrderedDict
 from collections.abc import Iterable
-from copy import deepcopy
 from numbers import Integral, Real
 from pathlib import Path
 from tempfile import TemporaryDirectory
@@ -138,8 +137,14 @@ class UniverseBase(ABC, IDManagerMixin):
 
         # If no memoize'd clone exists, instantiate one
         if self not in memo:
-            clone = deepcopy(self)
-            clone.id = None
+            clone = openmc.Universe(name=self.name)
+            clone.volume = self.volume
+            # Try to set DAGMCUniverse-specific attributes on the clone
+            try:
+                clone.auto_geom_ids = self.auto_geom_ids
+                clone.auto_mat_ids = self.auto_mat_ids
+            except AttributeError:
+                pass
 
             # Clone all cells for the universe clone
             clone._cells = OrderedDict()

tests/unit_tests/test_universe.py

@@ -120,6 +120,14 @@ def test_clone():
     assert next(iter(u3.cells.values())).region ==\
          next(iter(u1.cells.values())).region
 
+    dagmc_u = openmc.DAGMCUniverse(filename="")
+    dagmc_u.auto_geom_ids = True
+    dagmc_u.auto_mat_ids = True
+    dagmc_u1 = dagmc_u.clone()
+    assert dagmc_u1.name == dagmc_u.name
+    assert dagmc_u1.auto_geom_ids == dagmc_u.auto_geom_ids
+    assert dagmc_u1.auto_mat_ids == dagmc_u.auto_mat_ids
+
 
 def test_create_xml(cell_with_lattice):
     cells = [openmc.Cell() for i in range(5)]