Leverage retworkx for apply_operation* inner loop

qiskit/dagcircuit/dagcircuit.py

@@ -384,22 +384,11 @@ def apply_operation_back(self, op, qargs=None, cargs=None, condition=None):
         # Add new in-edges from predecessors of the output nodes to the
         # operation node while deleting the old in-edges of the output nodes
         # and adding new edges from the operation node to each output node
-        al = [qargs, all_cbits]
-        for q in itertools.chain(*al):
-            ie = self._multi_graph.predecessors(self.output_map[q]._node_id)
-
-            if len(ie) != 1:
-                raise DAGCircuitError("output node has multiple in-edges")
-
-            self._multi_graph.add_edge(
-                ie[0]._node_id, node_index,
-                {'name': "%s[%s]" % (q.register.name, q.index), 'wire': q})
-
-            self._multi_graph.remove_edge(ie[0]._node_id, self.output_map[q]._node_id)
-            self._multi_graph.add_edge(
-                node_index, self.output_map[q]._node_id,
-                dict(name="%s[%s]" % (q.register.name, q.index), wire=q))
 
+        al = [qargs, all_cbits]
+        self._multi_graph.insert_node_on_in_edges_multiple(
+            node_index,
+            [self.output_map[q]._node_id for q in itertools.chain(*al)])
         return self._multi_graph[node_index]
 
     def apply_operation_front(self, op, qargs, cargs, condition=None):
@@ -433,16 +422,9 @@ def apply_operation_front(self, op, qargs, cargs, condition=None):
         # operation node while deleting the old out-edges of the input nodes
         # and adding new edges to the operation node from each input node
         al = [qargs, all_cbits]
-        for q in itertools.chain(*al):
-            ie = self._multi_graph.successors(self.input_map[q]._node_id)
-            if len(ie) != 1:
-                raise DAGCircuitError("input node has multiple out-edges")
-            self._multi_graph.add_edge(node_index, ie[0]._node_id,
-                                       dict(name="%s[%s]" % (q.register.name, q.index), wire=q))
-            self._multi_graph.remove_edge(self.input_map[q]._node_id, ie[0]._node_id)
-            self._multi_graph.add_edge(self.input_map[q]._node_id, node_index,
-                                       dict(name="%s[%s]" % (q.register.name, q.index), wire=q))
-
+        self._multi_graph.insert_node_on_out_edges_multiple(
+            node_index,
+            [self.input_map[q]._node_id for q in itertools.chain(*al)])
         return self._multi_graph[node_index]
 
     def _check_edgemap_registers(self, edge_map, keyregs, valregs, valreg=True):

requirements.txt

@@ -1,7 +1,7 @@
 contextvars>=2.4;python_version<'3.7'
 jsonschema>=2.6
 networkx>=2.2
-retworkx>=0.5.0
+retworkx>=0.6.0
 numpy>=1.17
 ply>=3.10
 psutil>=5

setup.py

@@ -26,7 +26,7 @@
     "contextvars>=2.4;python_version<'3.7'",
     "jsonschema>=2.6",
     "networkx>=2.2",
-    "retworkx>=0.5.0",
+    "retworkx>=0.6.0",
     "numpy>=1.17",
     "ply>=3.10",
     "psutil>=5",