Merge pull request #580 from sandialabs/bugfix-deterministicFOGI

Bugfix deterministic fogi

Author: coreyostrove

pygsti/baseobjs/errorgenbasis.py

@@ -231,6 +231,7 @@ def overlaps(sslbls):
 
             sub_labels, sub_indices = zip(*[(lbl, i) for i, lbl in enumerate(self._labels)
                                             if overlaps(lbl[0])])
+            sub_sslbls = sorted(sub_sslbls)
             sub_state_space = self.state_space.create_subspace(sub_sslbls)
         else:
             sub_labels = []
@@ -262,7 +263,7 @@ def union(self, other_basis):
         #Get the union of the two bases labels.
         union_labels = set(self._labels) | set(other_basis.labels)
         union_state_space = self.state_space.union(other_basis.state_space)
-        return ExplicitElementaryErrorgenBasis(union_state_space, union_labels, self._basis_1q)
+        return ExplicitElementaryErrorgenBasis(union_state_space, sorted(union_labels, key=lambda label: label.__str__()), self._basis_1q)
 
     def intersection(self, other_basis):
         """
@@ -277,7 +278,7 @@ def intersection(self, other_basis):
 
         intersection_labels = set(self._labels) & set(other_basis.labels)
         intersection_state_space = self.state_space.intersection(other_basis.state_space)
-        return ExplicitElementaryErrorgenBasis(intersection_state_space, intersection_labels, self._basis_1q)
+        return ExplicitElementaryErrorgenBasis(intersection_state_space, sorted(intersection_labels, key=lambda label: label.__str__()), self._basis_1q)
 
     def difference(self, other_basis):
         """
@@ -295,7 +296,7 @@ def difference(self, other_basis):
         #that relied on the old (kind of incorrect behavior). Revert back to old version temporarily.
         #difference_state_space = self.state_space.difference(other_basis.state_space)
         difference_state_space = self.state_space
-        return ExplicitElementaryErrorgenBasis(difference_state_space, difference_labels, self._basis_1q)
+        return ExplicitElementaryErrorgenBasis(difference_state_space, sorted(difference_labels, key=lambda label: label.__str__()), self._basis_1q)
 
 class CompleteElementaryErrorgenBasis(ElementaryErrorgenBasis):
     """