Dependency Edge Hotfix (#1513)

This PR adds an additional check for dependency edges during codegen for
CPU and omits the copy operation generation accordingly.

---------

Co-authored-by: Tal Ben-Nun <[email protected]>
Co-authored-by: alexnick83 <[email protected]>

dace/codegen/targets/cpu.py

@@ -644,6 +644,9 @@ def _emit_copy(
         elif isinstance(src_node, nodes.CodeNode) and isinstance(dst_node, nodes.CodeNode):
             # Code->Code copy (not read nor write)
             raise RuntimeError("Copying between code nodes is only supported as part of the participating nodes")
+        elif uconn is None and vconn is None and memlet.data is None and dst_schedule == dtypes.ScheduleType.Sequential:
+            # Sequential dependency edge
+            return
         else:
             raise LookupError("Memlet does not point to any of the nodes")
 

tests/codegen/dependency_edge_test.py

@@ -0,0 +1,67 @@
+# Copyright 2019-2022 ETH Zurich and the DaCe authors. All rights reserved.
+
+import pytest
+import dace
+import numpy as np
+
+@pytest.mark.parametrize("reverse", [True, False])
+def test_mapped_dependency_edge(reverse):
+    """ Tests dependency edges in a map scope """
+
+    sdfg = dace.SDFG("mapped_dependency_edge")
+    state = sdfg.add_state()
+
+    sdfg.add_array("A", shape=[2], dtype=dace.int32)
+    sdfg.add_array("B", shape=[2], dtype=dace.int32)
+    sdfg.add_transient("tmp_A", shape=[1], dtype=dace.int32)
+    sdfg.add_transient("tmp_B", shape=[1], dtype=dace.int32)
+
+    map_entry, map_exit = state.add_map("map", {"i": "0:2"}, schedule=dace.dtypes.ScheduleType.Sequential)
+    map_entry.add_in_connector("IN_A")
+    map_entry.add_in_connector("IN_B")
+    map_entry.add_out_connector("OUT_A")
+    map_entry.add_out_connector("OUT_B")
+    map_exit.add_in_connector("IN_A")
+    map_exit.add_out_connector("OUT_A")
+
+    A1 = state.add_read("A")
+    A2 = state.add_write("A")
+    A3 = state.add_write("A")
+    A4 = state.add_write("A")
+    B = state.add_read("B")
+    tmp_A = state.add_write("tmp_A")
+    tmp_B = state.add_write("tmp_B")
+
+    state.add_edge(A1, None, map_entry, "IN_A", dace.Memlet("A[0:2]"))
+    state.add_edge(B, None, map_entry, "IN_B", dace.Memlet("B[0:2]"))
+
+    state.add_edge(map_entry, "OUT_A", tmp_A, None, dace.Memlet("A[i]"))
+    state.add_edge(map_entry, "OUT_B", tmp_B, None, dace.Memlet("B[i]"))
+
+    state.add_edge(tmp_A, None, A2, None, dace.Memlet("tmp_A[0] -> ((i+1)%2)"))
+    if not reverse:
+      state.add_edge(A2, None, tmp_B, None, dace.Memlet()) # Dependency Edge
+    state.add_edge(A2, None, map_exit, "IN_A", dace.Memlet("A[0:2]"))
+
+    state.add_edge(tmp_B, None, A3, None, dace.Memlet("tmp_B[0] -> ((i+1)%2)"))
+    if reverse:
+      state.add_edge(A3, None, tmp_A, None, dace.Memlet()) # Dependency Edge
+    state.add_edge(A3, None, map_exit, "IN_A", dace.Memlet("A[0:2]"))
+
+    state.add_edge(map_exit, "OUT_A", A4, None, dace.Memlet("A[0:2]"))
+
+    sdfg.validate()
+    a = np.random.randint(0, 100, 2).astype(np.int32)
+    b = np.random.randint(0, 100, 2).astype(np.int32)
+    sdfg(A=a, B=b)
+
+    if reverse:
+      assert a[0] == a[1]
+    else:
+      assert a[0] == b[1] and a[1] == b[0]
+
+
+if __name__ == "__main__":
+    test_mapped_dependency_edge(False)
+    test_mapped_dependency_edge(True)
+