fix of router hanging #2282 (#2619)

break if no adjacent connections
quantumlib · Dec 6, 2019 · 6d81ddb · 6d81ddb
1 parent 2b88d34
commit 6d81ddb
Showing 1 changed file with 7 additions and 1 deletion.
diff --git a/cirq/contrib/routing/greedy.py b/cirq/contrib/routing/greedy.py
@@ -284,7 +284,13 @@ def apply_next_swaps(self):
                 ]
                 if len(candidate_swap_sets) == 1:
                     self.apply_swap(*candidate_swap_sets[0])
-                    return
+
+                    if list(
+                            self.remaining_dag.findall_nodes_until_blocked(
+                                self.acts_on_nonadjacent_qubits)):
+                        return
+                    else:
+                        break
 
         frontier_edges = sorted(time_slices[0].edges)
         self.bring_farthest_pair_together(frontier_edges)