Fixes for TaskletFusion, AugAssignToWCR and MapExpansion (#1432)

- The PR fixes two minor bugs for corner cases of the AugAssignToWCR and
TaskletFusion which are reflected in additional test cases:
- TaskletFusion: Should not remove array from SDFG, since it could be
used elsewhere
- AugAssignToWCR: Handle tasklets where all inputs come from same array
- The PR re-writes MapExpansion to create only one memlet path per out
connector to be more efficient. I experienced MapExpansion running for
literally hours because it uses add_memlet_path for each edge to a
tasklet. This is too expensive for >4 dimensional stencils with >50
edges

dace/transformation/dataflow/map_expansion.py

@@ -3,13 +3,15 @@
 
 from dace.sdfg.utils import consolidate_edges
 from typing import Dict, List
+import copy
 import dace
 from dace import dtypes, subsets, symbolic
 from dace.properties import EnumProperty, make_properties
 from dace.sdfg import nodes
 from dace.sdfg import utils as sdutil
 from dace.sdfg.graph import OrderedMultiDiConnectorGraph
 from dace.transformation import transformation as pm
+from dace.sdfg.propagation import propagate_memlets_scope
 
 
 @make_properties
@@ -66,14 +68,28 @@ def apply(self, graph: dace.SDFGState, sdfg: dace.SDFG):
         # 1. If there are no edges coming from the outside, use empty memlets
         # 2. Edges with IN_* connectors replicate along the maps
         # 3. Edges for dynamic map ranges replicate until reaching range(s)
-        for edge in graph.out_edges(map_entry):
+        for edge in list(graph.out_edges(map_entry)):
+            if edge.src_conn is not None and edge.src_conn not in entries[-1].out_connectors:
+                entries[-1].add_out_connector(edge.src_conn)
+
+            graph.add_edge(entries[-1], edge.src_conn, edge.dst, edge.dst_conn, memlet=copy.deepcopy(edge.data))
             graph.remove_edge(edge)
-            graph.add_memlet_path(map_entry,
-                                  *entries,
-                                  edge.dst,
-                                  src_conn=edge.src_conn,
-                                  memlet=edge.data,
-                                  dst_conn=edge.dst_conn)
+
+        if graph.in_degree(map_entry) == 0:
+            graph.add_memlet_path(map_entry, *entries, memlet=dace.Memlet())
+        else:
+            for edge in graph.in_edges(map_entry):
+                if not edge.dst_conn.startswith("IN_"):
+                    continue
+
+                in_conn = edge.dst_conn
+                out_conn = "OUT_" + in_conn[3:]
+                if in_conn not in entries[-1].in_connectors:
+                    graph.add_memlet_path(map_entry,
+                                          *entries,
+                                          memlet=copy.deepcopy(edge.data),
+                                          src_conn=out_conn,
+                                          dst_conn=in_conn)
 
         # Modify dynamic map ranges
         dynamic_edges = dace.sdfg.dynamic_map_inputs(graph, map_entry)
@@ -116,6 +132,7 @@ def apply(self, graph: dace.SDFGState, sdfg: dace.SDFG):
         else:
             raise ValueError('Cannot find scope in state')
 
+        propagate_memlets_scope(sdfg, state=graph, scopes=scope)
         consolidate_edges(sdfg, scope)
 
         return [map_entry] + entries

dace/transformation/dataflow/tasklet_fusion.py

@@ -267,5 +267,5 @@ def apply(self, graph: dace.SDFGState, sdfg: dace.SDFG):
         graph.remove_node(t1)
         if data is not None:
             graph.remove_node(data)
-            sdfg.remove_data(data.data, True)
+
         graph.remove_node(t2)

dace/transformation/dataflow/wcr_conversion.py

@@ -75,6 +75,12 @@ def can_be_applied(self, graph, expr_index, sdfg, permissive=False):
 
             outedge = graph.edges_between(tasklet, mx)[0]
 
+            # If in map, only match if the subset is independent of any
+            # map indices (otherwise no conflict)
+            if not permissive and len(outedge.data.subset.free_symbols & set(me.map.params)) == len(
+                    me.map.params):
+                return False
+
         # Get relevant output connector
         outconn = outedge.src_conn
 
@@ -131,17 +137,7 @@ def can_be_applied(self, graph, expr_index, sdfg, permissive=False):
                 if edge.data.subset != outedge.data.subset:
                     continue
 
-                # If in map, only match if the subset is independent of any
-                # map indices (otherwise no conflict)
-                if expr_index == 1:
-                    if not permissive and len(outedge.data.subset.free_symbols & set(me.map.params)) == len(
-                            me.map.params):
-                        continue
-
                 return True
-        else:
-            # Only Python/C++ tasklets supported
-            return False
 
         return False
 
@@ -182,11 +178,13 @@ def apply(self, state: SDFGState, sdfg: SDFG):
             rhs: ast.BinOp = ast_node.value
             op = AugAssignToWCR._PYOP_MAP[type(rhs.op)]
             inconns = list(edge.dst_conn for edge in inedges)
-            for n in (rhs.left, rhs.right):
-                if isinstance(n, ast.Name) and n.id in inconns:
-                    inedge = inedges[inconns.index(n.id)]
-                else:
-                    new_rhs = n
+            if isinstance(rhs.left, ast.Name) and rhs.left.id in inconns:
+                inedge = inedges[inconns.index(rhs.left.id)]
+                new_rhs = rhs.right
+            else:
+                inedge = inedges[inconns.index(rhs.right.id)]
+                new_rhs = rhs.left
+
             new_node = ast.copy_location(ast.Assign(targets=[lhs], value=new_rhs), ast_node)
             tasklet.code.code = [new_node]
 

tests/transformations/map_expansion_test.py

@@ -0,0 +1,119 @@
+# Copyright 2019-2023 ETH Zurich and the DaCe authors. All rights reserved.
+import dace
+import numpy as np
+from dace.transformation.dataflow import MapExpansion
+
+def test_expand_with_inputs():
+    @dace.program
+    def toexpand(A: dace.float64[4, 2], B: dace.float64[2, 2]):
+        for i, j in dace.map[1:3, 0:2]:
+            with dace.tasklet:
+                a1 << A[i, j]
+                a2 << A[i + 1, j]
+                a3 << A[i - 1, j]
+                b >> B[i-1, j]
+                b = a1 + a2 + a3
+
+    sdfg = toexpand.to_sdfg()
+    sdfg.simplify()
+
+    # Init conditions
+    sdfg.validate()
+    assert len([node for node in sdfg.start_state.nodes() if isinstance(node, dace.nodes.MapEntry)]) == 1
+    assert len([node for node in sdfg.start_state.nodes() if isinstance(node, dace.nodes.MapExit)]) == 1
+
+    # Expansion
+    assert sdfg.apply_transformations_repeated(MapExpansion) == 1
+    sdfg.validate()
+
+    map_entries = set()
+    state = sdfg.start_state
+    for node in state.nodes():
+        if not isinstance(node, dace.nodes.MapEntry):
+            continue
+
+        # (Fast) MapExpansion should not add memlet paths for each memlet to a tasklet
+        if sdfg.start_state.entry_node(node) is None:
+            assert state.in_degree(node) == 1
+            assert state.out_degree(node) == 1
+            assert len(node.out_connectors) == 1
+        else:
+            assert state.in_degree(node) == 1
+            assert state.out_degree(node) == 3
+            assert len(node.out_connectors) == 1
+
+        map_entries.add(node)
+
+    assert len(map_entries) == 2
+
+def test_expand_without_inputs():
+    @dace.program
+    def toexpand(B: dace.float64[4, 4]):
+        for i, j in dace.map[0:4, 0:4]:
+            with dace.tasklet:
+                b >> B[i, j]
+                b = 0
+
+    sdfg = toexpand.to_sdfg()
+    sdfg.simplify()
+
+    # Init conditions
+    sdfg.validate()
+    assert len([node for node in sdfg.start_state.nodes() if isinstance(node, dace.nodes.MapEntry)]) == 1
+    assert len([node for node in sdfg.start_state.nodes() if isinstance(node, dace.nodes.MapExit)]) == 1
+
+    # Expansion
+    assert sdfg.apply_transformations_repeated(MapExpansion) == 1
+    sdfg.validate()
+
+    map_entries = set()
+    state = sdfg.start_state
+    for node in state.nodes():
+        if not isinstance(node, dace.nodes.MapEntry):
+            continue
+
+        # (Fast) MapExpansion should not add memlet paths for each memlet to a tasklet
+        if sdfg.start_state.entry_node(node) is None:
+            assert state.in_degree(node) == 0
+            assert state.out_degree(node) == 1
+            assert len(node.out_connectors) == 0
+        else:
+            assert state.in_degree(node) == 1
+            assert state.out_degree(node) == 1
+            assert len(node.out_connectors) == 0
+
+        map_entries.add(node)
+
+    assert len(map_entries) == 2
+
+def test_expand_without_dynamic_inputs():
+    @dace.program
+    def expansion(A: dace.float32[20, 30, 5], rng: dace.int32[2]):
+        @dace.map
+        def mymap(i: _[0:20], j: _[rng[0]:rng[1]], k: _[0:5]):
+            a << A[i, j, k]
+            b >> A[i, j, k]
+            b = a * 2
+
+    A = np.random.rand(20, 30, 5).astype(np.float32)
+    b = np.array([5, 10], dtype=np.int32)
+    expected = A.copy()
+    expected[:, 5:10, :] *= 2
+
+    sdfg = expansion.to_sdfg()
+    sdfg(A=A, rng=b)
+    diff = np.linalg.norm(A - expected)
+    print('Difference (before transformation):', diff)
+
+    sdfg.apply_transformations(MapExpansion)
+
+    sdfg(A=A, rng=b)
+    expected[:, 5:10, :] *= 2
+    diff2 = np.linalg.norm(A - expected)
+    print('Difference:', diff2)
+    assert (diff <= 1e-5) and (diff2 <= 1e-5)
+
+if __name__ == '__main__':
+    test_expand_with_inputs()
+    test_expand_without_inputs()
+    test_expand_without_dynamic_inputs()

tests/transformations/tasklet_fusion_test.py

@@ -3,6 +3,7 @@
 import dace
 from dace import dtypes
 from dace.transformation.dataflow import TaskletFusion, MapFusion
+from dace.transformation.optimizer import Optimizer
 import pytest
 
 datatype = dace.float32
@@ -257,6 +258,33 @@ def sdfg_none_connector(A: dace.float32[32], B: dace.float32[32]):
     assert sdfg.start_state.out_degree(map_entry) == 1
     assert len([edge.src_conn for edge in sdfg.start_state.out_edges(map_entry) if edge.src_conn is None]) == 0
 
+
+def test_intermediate_transients():
+    @dace.program
+    def sdfg_intermediate_transients(A: dace.float32[10], B: dace.float32[10]):
+        tmp = dace.define_local_scalar(dace.float32)
+
+        # Use tmp twice to test removal of data
+        tmp = A[0] + 1
+        tmp = tmp * 2
+        B[0] = tmp
+
+
+    sdfg = sdfg_intermediate_transients.to_sdfg(simplify=True)
+    assert len([node for node in sdfg.start_state.data_nodes() if node.data == "tmp"]) == 2
+
+    xforms = Optimizer(sdfg=sdfg).get_pattern_matches(patterns=(TaskletFusion,))
+    applied = False
+    for xform in xforms:
+        if xform.data.data == "tmp":
+            xform.apply(sdfg.start_state, sdfg)
+            applied = True
+            break
+
+    assert applied
+    assert len([node for node in sdfg.start_state.data_nodes() if node.data == "tmp"]) == 1
+    assert "tmp" in sdfg.arrays
+
 if __name__ == '__main__':
     test_basic()
     test_same_name()
@@ -268,3 +296,4 @@ def sdfg_none_connector(A: dace.float32[32], B: dace.float32[32]):
     test_map_with_tasklets(language='CPP', with_data=False)
     test_map_with_tasklets(language='CPP', with_data=True)
     test_none_connector()
+    test_intermediate_transients()

tests/transformations/wcr_conversion_test.py

@@ -245,3 +245,21 @@ def sdfg_free_map_permissive(A: dace.float64[32], B: dace.float64[32]):
 
     applied = sdfg.apply_transformations_repeated(AugAssignToWCR, permissive=True)
     assert applied == 1
+
+def test_aug_assign_same_inconns():
+
+    @dace.program
+    def sdfg_aug_assign_same_inconns(A: dace.float64[32]):
+        for i in dace.map[0:31]:
+            with dace.tasklet(language=dace.Language.Python):
+                a << A[i]
+                b << A[i+1]
+                c >> A[i]
+
+                c = a * b
+
+    sdfg = sdfg_aug_assign_same_inconns.to_sdfg()
+    sdfg.simplify()
+
+    applied = sdfg.apply_transformations_repeated(AugAssignToWCR, permissive=True)
+    assert applied == 1