Remove regular expression re-compiles

- The only thing that changes about the regular expression is the prefix
- We can also detect the prefix with startswith, and then use the same
  regular expression across the loop
- This means that Python can cache the compiled regex internally, and we
  save some time

Author: HippocampusGirl

nipype/pipeline/engine/utils.py

@@ -1100,11 +1100,12 @@ def make_field_func(*pair):
             old_edge_dict = jedge_dict[jnode]
             # the edge source node replicates
             expansions = defaultdict(list)
-            for node in graph_in.nodes():
+            for node in graph_in:
                 for src_id in list(old_edge_dict.keys()):
                     # Drop the original JoinNodes; only concerned with
                     # generated Nodes
-                    if hasattr(node, "joinfield") and node.itername == src_id:
+                    itername = node.itername
+                    if hasattr(node, "joinfield") and itername == src_id:
                         continue
                     # Patterns:
                     #   - src_id : Non-iterable node
@@ -1113,10 +1114,12 @@ def make_field_func(*pair):
                     #   - src_id.[a-z]I.[a-z]\d+ :
                     #       Non-IdentityInterface w/ iterables
                     #   - src_idJ\d+ : JoinNode(IdentityInterface)
-                    if re.match(
-                        src_id + r"((\.[a-z](I\.[a-z])?|J)\d+)?$", node.itername
-                    ):
-                        expansions[src_id].append(node)
+                    if itername.startswith(src_id):
+                        itername = itername[len(src_id):]
+                        if re.fullmatch(
+                            r"((\.[a-z](I\.[a-z])?|J)\d+)?", itername
+                        ):
+                            expansions[src_id].append(node)
             for in_id, in_nodes in list(expansions.items()):
                 logger.debug(
                     "The join node %s input %s was expanded" " to %d nodes.",