faster fanout generator function

src/kyupy/circuit.py

@@ -614,20 +614,24 @@ class Circuit:
             if marks[n]:
                 yield n
 
-    def fanout(self, origin_nodes):
+    def fanout(self, origin_nodes: list[Node], node_filter = lambda n: 'dff' not in n.name.lower()):
         """Generator function to iterate over the fan-out cone of a given list of origin nodes.
 
-        Nodes are yielded in topological order.
+        origin_nodes are yielded first, followed by nodes driven by them in a breadth-first manner.
+        The search stops at nodes for which node_filter returns False.
+        Only origin_nodes and nodes for which node_filter returned True are yielded.
+        By default, search stops at flip-flops.
         """
-        marks = [False] * len(self.nodes)
-        for n in origin_nodes:
-            marks[n] = True
-        for n in self.topological_order():
-            if not marks[n]:
-                for line in n.ins.without_nones():
-                    marks[n] |= marks[line.driver]
-            if marks[n]:
-                yield n
+        queue = deque(origin_nodes)
+        yielded = set()
+        while len(queue) > 0:
+            n = queue.popleft()
+            for line in n.outs.without_nones():
+                succ = line.reader
+                if succ not in yielded and node_filter(succ):
+                    yielded.add(succ)
+                    queue.append(succ)
+            yield n
 
     def fanout_free_regions(self):
         for stem in self.reversed_topological_order():