added get_all_dag_edges_between function

src/copapy/_compiler.py

@@ -55,6 +55,43 @@ def stable_toposort(edges: Iterable[tuple[Node, Node]]) -> list[Node]:
     return result
 
 
+def get_all_dag_edges_between(roots: Iterable[Node], leaves: Iterable[Node]) -> Generator[tuple[Node, Node], None, None]:
+    """Get all edges in the DAG connecting given roots with given leaves
+
+    Arguments:
+        nodes: Iterable of nodes to start the traversal from
+
+    Yields:
+        Tuples of (source_node, target_node) representing edges in the DAG
+    """
+    # Walk the full DAG starting from given roots to final leaves
+    parent_lookup: dict[Node, set[Node]] = dict()
+    node_list: list[Node] = [n for n in roots]
+    while(node_list):
+        node = node_list.pop()
+        for net in node.args:
+            if net.source in parent_lookup:
+                parent_lookup[net.source].add(node)
+            else:
+                parent_lookup[net.source] = {node}
+                node_list.append(net.source)
+
+    # Walk the DAG in reverse direction starting from given leaves to given roots
+    emitted_edges: set[tuple[Node, Node]] = set()
+    node_list = [n for n in leaves]
+    while(node_list):
+        child_node = node_list.pop()
+        if child_node in parent_lookup:
+            for node in parent_lookup[child_node]:
+                edge = (child_node, node)
+                if edge not in emitted_edges:
+                    yield edge
+                    node_list.append(node)
+                    emitted_edges.add(edge)
+
+    assert all(r in {e[0] for e in emitted_edges} for r in leaves)
+
+
 def get_all_dag_edges(nodes: Iterable[Node]) -> Generator[tuple[Node, Node], None, None]:
     """Get all edges in the DAG by traversing from the given nodes
 
@@ -64,15 +101,17 @@ def get_all_dag_edges(nodes: Iterable[Node]) -> Generator[tuple[Node, Node], Non
     Yields:
         Tuples of (source_node, target_node) representing edges in the DAG
     """
-    emitted_nodes: set[tuple[Node, Node]] = set()
+    emitted_edges: set[tuple[Node, Node]] = set()
+    node_list: list[Node] = [n for n in nodes]
 
-    for node in nodes:
-        yield from get_all_dag_edges(net.source for net in node.args)
+    while(node_list):
+        node = node_list.pop()
         for net in node.args:
             edge = (net.source, node)
-            if edge not in emitted_nodes:
+            if edge not in emitted_edges:
                 yield edge
-                emitted_nodes.add(edge)
+                node_list.append(net.source)
+                emitted_edges.add(edge)
 
 
 def get_const_nets(nodes: list[Node]) -> list[Net]:

src/copapy/backend.py

@@ -1,7 +1,7 @@
 from ._target import add_read_command
 from ._basic_types import Net, Op, Node, CPConstant, Write, stencil_db_from_package
 from ._compiler import compile_to_dag, \
-    stable_toposort, get_const_nets, get_all_dag_edges, add_read_ops, \
+    stable_toposort, get_const_nets, get_all_dag_edges, add_read_ops, get_all_dag_edges_between, \
     add_write_ops
 
 __all__ = [
@@ -15,6 +15,7 @@ __all__ = [
     "stable_toposort",
     "get_const_nets",
     "get_all_dag_edges",
+    "get_all_dag_edges_between",
     "add_read_ops",
     "add_write_ops",
     "stencil_db_from_package"