get_subgraph_outputs (towards checking that intermediate nodes in a matched graph not used) (#1207)

* get_subgraph_outputs

* simplify the condition

src/ngraph/graph_util.cpp

@@ -465,6 +465,33 @@ bool ngraph::is_one(std::shared_ptr<Node> reduce_constant)
     return result_bool;
 }
 
+NodeVector ngraph::get_subgraph_outputs(const NodeVector& nodes,
+                                        const NodeVector& exclusions,
+                                        bool ignore_unused)
+{
+    std::set<shared_ptr<Node>> exclusions_set(exclusions.begin(), exclusions.end());
+    std::set<shared_ptr<Node>> nodes_set(nodes.begin(), nodes.end());
+
+    NodeVector outputs;
+
+    for (auto n : nodes)
+    {
+        if (exclusions_set.count(n) != 0)
+        {
+            continue;
+        }
+
+        for (auto u : n->get_users())
+        {
+            if (nodes_set.count(u) == 0 && (!ignore_unused || is_used(u.get())))
+            {
+                outputs.push_back(n);
+            }
+        }
+    }
+    return outputs;
+}
+
 bool ngraph::is_used(Node* node)
 {
     std::unordered_set<Node*> instances_seen;

src/ngraph/graph_util.hpp

@@ -133,6 +133,10 @@ namespace ngraph
 
     bool is_zero(std::shared_ptr<Node> reduce_constant);
 
+    NodeVector get_subgraph_outputs(const NodeVector& nodes,
+                                    const NodeVector& exclusions,
+                                    bool ignore_unused = false);
+
     bool is_one(std::shared_ptr<Node> reduce_constant);
 
     // Returns true if `node` is live in the graph i.e. a result op

test/util.cpp

@@ -324,3 +324,44 @@ TEST(util, parse_string)
     EXPECT_FLOAT_EQ(-numeric_limits<double>::infinity(), parse_string<double>("-INFINITY"));
     EXPECT_TRUE(std::isnan(parse_string<double>("NaN")));
 }
+
+TEST(graph_util, get_subgraph_outputs_trivial_tests)
+{
+    auto outputs = ngraph::get_subgraph_outputs(NodeVector{}, NodeVector{});
+    ASSERT_EQ(outputs.size(), 0);
+
+    Shape shape{};
+    auto A = make_shared<op::Parameter>(element::f32, shape);
+    auto absn = make_shared<op::Abs>(A);
+    auto neg_absn = make_shared<op::Negative>(absn);
+    outputs = ngraph::get_subgraph_outputs(NodeVector{A}, NodeVector{});
+    ASSERT_EQ(outputs, (NodeVector{A}));
+
+    outputs = ngraph::get_subgraph_outputs(NodeVector{A}, NodeVector{A});
+    ASSERT_EQ(outputs, (NodeVector{}));
+
+    outputs = ngraph::get_subgraph_outputs(NodeVector{A, absn}, NodeVector{});
+    ASSERT_EQ(outputs, (NodeVector{absn}));
+
+    auto B = make_shared<op::Parameter>(element::f32, shape);
+    auto abs_b = make_shared<op::Abs>(B);
+    auto neg_b = make_shared<op::Negative>(B);
+    auto abs_b_neg = make_shared<op::Negative>(abs_b);
+    outputs = ngraph::get_subgraph_outputs(NodeVector{B, abs_b}, NodeVector{});
+    ASSERT_EQ(outputs, (NodeVector{B, abs_b}));
+
+    outputs = ngraph::get_subgraph_outputs(NodeVector{B, abs_b}, NodeVector{B});
+    ASSERT_EQ(outputs, (NodeVector{abs_b}));
+
+    outputs = ngraph::get_subgraph_outputs(NodeVector{B, abs_b, abs_b_neg}, NodeVector{});
+    ASSERT_EQ(outputs, (NodeVector{B}));
+
+    auto add_b = make_shared<op::Add>(neg_b, abs_b_neg);
+    outputs =
+        ngraph::get_subgraph_outputs(NodeVector{B, abs_b, neg_b, abs_b_neg, add_b}, NodeVector{});
+    ASSERT_EQ(outputs, (NodeVector{}));
+
+    //now add_b uses abs_b_neg
+    outputs = ngraph::get_subgraph_outputs(NodeVector{B, abs_b, abs_b_neg}, NodeVector{});
+    ASSERT_EQ(outputs, (NodeVector{B, abs_b_neg}));
+}