test and doc IR Graph

paddle/fluid/framework/ir/graph.h

@@ -28,6 +28,38 @@ namespace paddle {
 namespace framework {
 namespace ir {
 
+/*
+ * The graph is a Directed Acyclic Single Static Assignment Graph.
+ *
+ * In more detail, the following properties must hold:
+ *
+ *   The graph shouldn't contain cycle. Each node is a black-box to the graph
+ *   so the node itself could be a loop operator.
+ *
+ *   Each Variable-type node has only one input (thus single static assignment).
+ *
+ *   The output/input of operator is variable and the output/input of variable
+ *   is operator.
+ *
+ * The following data harzards in Program are addressed in the Graph:
+ *
+ *   Write-After-Read
+ *     a = op1(x)
+ *     x = op2(b)
+ *     A control-dependency connection is created bettwen op1 and op2 such that
+ *     op1->op2, so as to ensure correct order.
+ *
+ *   Write-After-Write
+ *     x = op1(a)
+ *     x = op2(b)
+ *     A control-dependency connection is created between op1 and op2 such that
+ *     op1->op2, so as to ensure correct order.
+ *
+ * Other properties currently hold, but is not enforced yet:
+ *
+ *   Variable-type node (not control dep) with the same variable name share
+ *   the same underlying VarDesc.
+ */
 class Graph {
  public:
   explicit Graph(const ProgramDesc &program);

paddle/fluid/framework/ir/graph_test.cc

@@ -36,7 +36,7 @@ class SumOpMaker : public OpProtoAndCheckerMaker {
  public:
   void Make() {
     AddInput("X", "").AsDuplicable();
-    AddOutput("Out", "");
+    AddOutput("Out", "").AsDuplicable();
     AddComment("");
   }
 };
@@ -59,11 +59,27 @@ class SumOpVarTypeInference : public VarTypeInference {
     block->Var(out_var_name)->SetType(default_var_type);
   }
 };
+
+class DummyOpMaker : public OpProtoAndCheckerMaker {
+ public:
+  void Make() {
+    AddInput("X", "").AsDuplicable();
+    AddOutput("Out", "").AsDuplicable();
+    AddComment("");
+  }
+};
+
+class DummyOpVarTypeInference : public VarTypeInference {
+ public:
+  void operator()(const OpDesc &op_desc, BlockDesc *block) const override {}
+};
 }  // namespace framework
 }  // namespace paddle
 
 REGISTER_OPERATOR(sum, paddle::framework::NOP, paddle::framework::SumOpMaker,
                   paddle::framework::SumOpVarTypeInference);
+REGISTER_OPERATOR(dummy, paddle::framework::NOP, paddle::framework::SumOpMaker,
+                  paddle::framework::SumOpVarTypeInference);
 REGISTER_OPERATOR(sum_without_infer_var_type, paddle::framework::NOP,
                   paddle::framework::SumOpMaker);
 
@@ -110,5 +126,83 @@ TEST(GraphTest, Basic) {
   }
   ASSERT_EQ(nodes.size(), 5);
 }
+
+TEST(GraphTest, WriteAfterRead) {
+  // void Test() {
+  ProgramDesc prog;
+  auto *op = prog.MutableBlock(0)->AppendOp();
+  op->SetType("sum");
+  op->SetInput("X", {"a"});
+  op->SetOutput("Out", {"b"});
+  op->SetAttr("op_role", 1);
+
+  op = prog.MutableBlock(0)->AppendOp();
+  op->SetType("dummy");
+  op->SetInput("X", {"c"});
+  op->SetOutput("Out", {"a"});
+  op->SetAttr("op_role", 1);
+
+  prog.MutableBlock(0)->Var("a")->SetType(proto::VarType::LOD_TENSOR);
+  prog.MutableBlock(0)->Var("b")->SetType(proto::VarType::LOD_TENSOR);
+  prog.MutableBlock(0)->Var("c")->SetType(proto::VarType::LOD_TENSOR);
+
+  std::unique_ptr<ir::Graph> g(new ir::Graph(prog));
+  ir::Node *control_dep1 = nullptr;
+  ir::Node *control_dep2 = nullptr;
+  for (ir::Node *n : g->Nodes()) {
+    if (n->Name() == "sum") {
+      ASSERT_EQ(n->outputs[0]->Name(), "b");
+      ASSERT_TRUE(ir::IsControlDepVar(*n->outputs[1]));
+      control_dep1 = n->outputs[1];
+      ASSERT_EQ(n->outputs.size(), 2);
+    }
+    if (n->Name() == "dummy") {
+      ASSERT_EQ(n->inputs[0]->Name(), "c");
+      ASSERT_TRUE(ir::IsControlDepVar(*n->inputs[1]));
+      control_dep2 = n->inputs[1];
+      ASSERT_EQ(n->inputs.size(), 2);
+    }
+  }
+  ASSERT_EQ(control_dep1, control_dep2);
+}
+
+TEST(GraphTest, WriteAfterWrite) {
+  // void Test() {
+  ProgramDesc prog;
+  auto *op = prog.MutableBlock(0)->AppendOp();
+  op->SetType("sum");
+  op->SetInput("X", {"a"});
+  op->SetOutput("Out", {"b"});
+  op->SetAttr("op_role", 1);
+
+  op = prog.MutableBlock(0)->AppendOp();
+  op->SetType("dummy");
+  op->SetInput("X", {"c"});
+  op->SetOutput("Out", {"b"});
+  op->SetAttr("op_role", 1);
+
+  prog.MutableBlock(0)->Var("a")->SetType(proto::VarType::LOD_TENSOR);
+  prog.MutableBlock(0)->Var("b")->SetType(proto::VarType::LOD_TENSOR);
+  prog.MutableBlock(0)->Var("c")->SetType(proto::VarType::LOD_TENSOR);
+
+  std::unique_ptr<ir::Graph> g(new ir::Graph(prog));
+  ir::Node *control_dep1 = nullptr;
+  ir::Node *control_dep2 = nullptr;
+  for (ir::Node *n : g->Nodes()) {
+    if (n->Name() == "sum") {
+      ASSERT_EQ(n->outputs[0]->Name(), "b");
+      ASSERT_TRUE(ir::IsControlDepVar(*n->outputs[1]));
+      ASSERT_EQ(n->outputs.size(), 2);
+      control_dep1 = n->outputs[1];
+    }
+    if (n->Name() == "dummy") {
+      ASSERT_EQ(n->inputs[0]->Name(), "c");
+      ASSERT_TRUE(ir::IsControlDepVar(*n->inputs[1]));
+      control_dep2 = n->inputs[1];
+      ASSERT_EQ(n->inputs.size(), 2);
+      ASSERT_EQ(control_dep1, control_dep2);
+    }
+  }
+}
 }  // namespace framework
 }  // namespace paddle