Fixed remove_edge_and_dangling_path()

dace/sdfg/nodes.py

@@ -192,11 +192,17 @@ def remove_in_connector(self, connector_name: str):
             :param connector_name: The name of the connector to remove.
             :return: True if the operation was successful.
         """
+        if not connector_name:
+            warnings.warn(f'Tried to remove the {connector_name} from the in-connectors of node {str(self)}',
+                          stacklevel=1)
+            return False
+
+        if connector_name not in self.in_connectors:
+            return False
 
-        if connector_name in self.in_connectors:
-            connectors = self.in_connectors
-            del connectors[connector_name]
-            self.in_connectors = connectors
+        connectors = self.in_connectors
+        del connectors[connector_name]
+        self.in_connectors = connectors
         return True
 
     def remove_out_connector(self, connector_name: str):
@@ -205,11 +211,17 @@ def remove_out_connector(self, connector_name: str):
             :param connector_name: The name of the connector to remove.
             :return: True if the operation was successful.
         """
+        if not connector_name:
+            warnings.warn(f'Tried to remove the {connector_name} from the out-connectors of node {str(self)}',
+                          stacklevel=1)
+            return False
+
+        if connector_name not in self.out_connectors:
+            return False
 
-        if connector_name in self.out_connectors:
-            connectors = self.out_connectors
-            del connectors[connector_name]
-            self.out_connectors = connectors
+        connectors = self.out_connectors
+        del connectors[connector_name]
+        self.out_connectors = connectors
         return True
 
     def _next_connector_int(self) -> int:

dace/sdfg/utils.py

@@ -857,51 +857,74 @@ def set_outer_subset(e: MultiConnectorEdge[dace.Memlet], new_subset: sbs.Subset)
     return consolidated
 
 
-def remove_edge_and_dangling_path(state: SDFGState, edge: MultiConnectorEdge):
+def remove_edge_and_dangling_path(state: SDFGState, edge: MultiConnectorEdge) -> int:
     """
-    Removes an edge and all of its parent edges in a memlet path, cleaning
-    dangling connectors and isolated nodes resulting from the removal.
+    Removes an edge and all of its parent edges in a memlet path, including now
+    unused connectors. Furthermore, all nodes that become isolated are also
+    removed from the state.
 
     :param state: The state in which the edge exists.
     :param edge: The edge to remove.
     """
-    mtree = state.memlet_tree(edge)
-    inwards = (isinstance(edge.src, nd.EntryNode) or isinstance(edge.dst, nd.EntryNode))
+
+    if edge.data.is_empty():
+        state.remove_edge(edge)
+        if state.degree(edge.dst) == 0:
+            state.remove_node(edge.dst)
+        if state.degree(edge.src) == 0:
+            state.remove_node(edge.src)
+        return 1
 
     # Traverse tree upwards, removing edges and connectors as necessary
-    curedge = mtree
-    while curedge is not None:
-        e = curedge.edge
-        state.remove_edge(e)
-        if inwards:
-            neighbors = [] if not e.src_conn else [
-                neighbor for neighbor in state.out_edges_by_connector(e.src, e.src_conn)
-            ]
-        else:
-            neighbors = [] if not e.dst_conn else [
-                neighbor for neighbor in state.in_edges_by_connector(e.dst, e.dst_conn)
-            ]
-        if len(neighbors) > 0:  # There are still edges connected, leave as-is
-            break
+    mtree = state.memlet_tree(edge)
+    curr_tree = mtree
+    nb_removed_edges = 0
+    while curr_tree is not None:
+        curr_edge = curr_tree.edge
+        assert not curr_edge.data.is_empty()
+        state.remove_edge(curr_edge)
+        nb_removed_edges += 1
+
+        if curr_tree.downwards:
+            if state.degree(curr_edge.dst) == 0:
+                # If the edge is isolated we can remove it.
+                state.remove_node(curr_edge.dst)
+            else:
+                # If the node is not isolated we must look at its connectors and clean them.
+                if isinstance(curr_edge.dst, nd.EntryNode) and curr_edge.dst_conn.startswith("IN_"):
+                    curr_edge.dst.remove_out_connector("OUT_" + curr_edge.dst_conn[3:])
+                if curr_edge.dst_conn and len(list(state.in_edges_by_connector(curr_edge.dst,
+                                                                               curr_edge.dst_conn))) == 0:
+                    curr_edge.dst.remove_in_connector(curr_edge.dst_conn)
 
-        # Remove connector and matching outer connector
-        if inwards:
-            if e.src_conn:
-                e.src.remove_out_connector(e.src_conn)
-                e.src.remove_in_connector('IN' + e.src_conn[3:])
-        else:
-            if e.dst_conn:
-                e.dst.remove_in_connector(e.dst_conn)
-                e.dst.remove_out_connector('OUT' + e.dst_conn[2:])
+            # There is a fan-out, i.e. the `curr_edge.src_conn` is still in use and we are done here.
+            if len(list(state.out_edges_by_connector(curr_edge.src, curr_edge.src_conn))) != 0:
+                return nb_removed_edges
 
-        # Continue traversing upwards
-        curedge = curedge.parent
-    else:
-        # Check if an isolated node have been created at the root and remove
-        root_edge = mtree.root().edge
-        root_node: nd.Node = root_edge.src if inwards else root_edge.dst
-        if state.degree(root_node) == 0:
-            state.remove_node(root_node)
+        else:
+            if state.degree(curr_edge.src) == 0:
+                state.remove_node(curr_edge.src)
+            else:
+                if isinstance(curr_edge.src, nd.ExitNode) and curr_edge.src_conn.startswith("OUT_"):
+                    curr_edge.src.remove_in_connector("IN_" + curr_edge.src_conn[4:])
+                if curr_edge.src_conn and len(list(state.out_edges_by_connector(curr_edge.src,
+                                                                                curr_edge.src_conn))) == 0:
+                    curr_edge.src.remove_out_connector(curr_edge.src_conn)
+
+            # The connector might be collecting.
+            if len(list(state.in_edges_by_connector(curr_edge.dst, curr_edge.dst_conn))) != 0:
+                return nb_removed_edges
+
+        # Continue traversing tree upwards
+        curr_tree = curr_tree.parent
+
+    # Check if an isolated node have been created at the root and remove
+    root_edge = mtree.root().edge
+    root_node: nd.Node = root_edge.src if mtree.downwards else root_edge.dst
+    if state.degree(root_node) == 0:
+        state.remove_node(root_node)
+
+    return nb_removed_edges
 
 
 def consolidate_edges(

tests/sdfg/remove_edge_and_dangling_path_test.py

@@ -0,0 +1,131 @@
+# Copyright 2019-2026 ETH Zurich and the DaCe authors. All rights reserved.
+import dace
+
+
+def test_remove_edge_global_scope():
+    sdfg = dace.SDFG("simple_edge_remover_test")
+    state = sdfg.add_state()
+
+    sdfg.add_array("a", shape=(1, ), dtype=dace.float64, transient=False)
+    sdfg.add_array("b", shape=(1, ), dtype=dace.float64, transient=False)
+
+    tlet = state.add_tasklet(
+        "comp",
+        inputs={"__in"},
+        outputs={"__out"},
+        code="__out = __in + 1.0",
+    )
+    a = state.add_access("a")
+    b = state.add_access("b")
+
+    up_edge = state.add_edge(a, None, tlet, "__in", dace.Memlet("a[0]"))
+    down_edge = state.add_edge(tlet, "__out", b, None, dace.Memlet("b[0]"))
+    sdfg.validate()
+
+    # Now remove the edge using the function. Note that this makes the SDFG invalid,
+    #  because the tasklet wants an input. We ignore that for now.
+    nb_removed_edges = dace.sdfg.utils.remove_edge_and_dangling_path(state, up_edge)
+    assert nb_removed_edges == 1
+    assert a not in state.nodes()
+    assert tlet in state.nodes()
+    assert b in state.nodes()
+    assert sdfg.arrays.keys() == {"a", "b"}
+    assert len(tlet.in_connectors) == 0
+    assert state.in_degree(tlet) == 0
+    assert tlet.out_connectors.keys() == {"__out"}
+    assert state.out_degree(tlet) == 1
+
+    # If we now also delete the `down_edge` then the state will become empty.
+    nb_removed_edges = dace.sdfg.utils.remove_edge_and_dangling_path(state, down_edge)
+    assert nb_removed_edges == 1
+    assert state.number_of_nodes() == 0
+
+
+def test_remove_edge_nested_scope():
+    sdfg = dace.SDFG("nested_edge_remover_test")
+    state = sdfg.add_state()
+
+    sdfg.add_array("a", shape=(10, 10), dtype=dace.float64, transient=False)
+    sdfg.add_array("b", shape=(10, 10, 2), dtype=dace.float64, transient=False)
+
+    tlet = state.add_tasklet(
+        "comp",
+        inputs={"__in1", "__in2"},
+        outputs={"__out1", "__out2"},
+        code="__out1 = __in1 + 1.0\n__out2 = __in2 - 1.0",
+    )
+    a, b = (state.add_access(name) for name in "ab")
+    me, mx = state.add_map("outer_map", ndrange={"__i": "0:10"})
+    nme, nmx = state.add_map("nested_map", ndrange={"__j": "0:10"})
+
+    state.add_edge(a, None, me, "IN_a", dace.Memlet("a[0:10, 0:10]"))
+    me.add_scope_connectors("a")
+    state.add_edge(me, "OUT_a", nme, "IN_a1", dace.Memlet("a[__i, 0:10]"))
+    state.add_edge(me, "OUT_a", nme, "IN_a2", dace.Memlet("a[0:10, __i]"))
+    nme.add_scope_connectors("a1")
+    nme.add_scope_connectors("a2")
+
+    up_edge1 = state.add_edge(nme, "OUT_a1", tlet, "__in1", dace.Memlet("a[__i, __j]"))
+    up_edge2 = state.add_edge(nme, "OUT_a2", tlet, "__in2", dace.Memlet("a[__j, __i]"))
+
+    down_edge1 = state.add_edge(tlet, "__out1", nmx, "IN_b", dace.Memlet("b[__i, __j, 0]"))
+    down_edge2 = state.add_edge(tlet, "__out2", nmx, "IN_b", dace.Memlet("b[__j, __i, 1]"))
+    nmx.add_scope_connectors("b")
+
+    state.add_edge(nmx, "OUT_b", mx, "IN_b", dace.Memlet("b[0:10, 0:10, 0:2]"))
+    mx.add_scope_connectors("b")
+    state.add_edge(mx, "OUT_b", b, None, dace.Memlet("b[0:10, 0:10, 0:2]"))
+    sdfg.validate()
+
+    assert state.number_of_nodes() == 7
+
+    # Because of the fan out, the deletion will stop.
+    nb_rm_up_edge1 = dace.sdfg.utils.remove_edge_and_dangling_path(state, up_edge1)
+    assert nb_rm_up_edge1 == 2
+    assert state.number_of_nodes() == 7
+    assert set(tlet.in_connectors.keys()) == {"__in2"}
+    assert state.in_degree(tlet) == 1
+    assert set(tlet.out_connectors.keys()) == {"__out1", "__out2"}
+    assert state.out_degree(tlet) == 2
+    assert set(nme.out_connectors.keys()) == {"OUT_a2"}
+    assert set(nme.in_connectors.keys()) == {"IN_a2"}
+    assert state.out_degree(nme) == 1
+    assert state.in_degree(nme) == 1
+    assert state.out_degree(me) == 1
+    assert state.in_degree(me) == 1
+    assert set(me.out_connectors.keys()) == {"OUT_a"}
+    assert set(me.in_connectors.keys()) == {"IN_a"}
+    assert state.degree(a) == 1
+
+    # Now the deletion will go up and remove the map entries; which leads to a
+    #  technical and functional invalid SDFG.
+    nb_rm_up_edge2 = dace.sdfg.utils.remove_edge_and_dangling_path(state, up_edge2)
+    assert nb_rm_up_edge2 == 3
+    assert state.number_of_nodes() == 4
+    assert state.number_of_edges() == 4
+    assert {tlet, nmx, mx, b} == set(state.nodes())
+    assert len(tlet.in_connectors) == 0
+    assert set(tlet.out_connectors.keys()) == {"__out1", "__out2"}
+
+    # The first down edge, will only delete one edge, due to the location of the fan
+    #  in, which is a bit different compared to the location of the upper fan out.
+    nb_rm_down_edge1 = dace.sdfg.utils.remove_edge_and_dangling_path(state, down_edge1)
+    assert nb_rm_down_edge1 == 1
+    assert state.number_of_nodes() == 4
+    assert state.number_of_edges() == 3
+    assert {tlet, nmx, mx, b} == set(state.nodes())
+    assert len(tlet.in_connectors) == 0
+    assert set(tlet.out_connectors.keys()) == {"__out2"}
+    assert len(nmx.in_connectors) == 1
+    assert len(nmx.out_connectors) == 1
+    assert len(mx.in_connectors) == 1
+    assert len(mx.out_connectors) == 1
+
+    # This will remove all nodes.
+    nb_rm_down_edge2 = dace.sdfg.utils.remove_edge_and_dangling_path(state, down_edge2)
+    assert nb_rm_up_edge2 == 3
+    assert state.number_of_nodes() == 0
+
+
+if __name__ == '__main__':
+    test_remove_edge_global_scope()