faster topological sort (#1886)

src/ngraph/descriptor/input.hpp

@@ -42,6 +42,8 @@ namespace ngraph
             /// \return the node that this is an input of
             std::shared_ptr<Node> get_node() const;
 
+            /// \return the raw pointer to the node that this is an input of
+            Node* get_raw_pointer_node() const { return m_node; }
             /// \return the position within all supplied tensors of this input
             size_t get_index() const { return m_index; }
             /// \return the connected output

src/ngraph/graph_util.hpp

@@ -75,13 +75,13 @@ namespace ngraph
             {
                 for (auto cd : node->get_control_dependencies())
                 {
+                    control_deps_count++;
                     control_deps_users[cd.get()].insert(node.get());
                 }
-                control_deps_count = node->get_control_dependencies().size();
             }
 
             node_map[node.get()] = node;
-            size_t deps_count = node->get_arguments().size() + control_deps_count;
+            size_t deps_count = node->get_inputs().size() + control_deps_count;
             node_dependency_count[node.get()] = deps_count;
             if (deps_count == 0)
             {
@@ -96,9 +96,11 @@ namespace ngraph
             result_list.push_back(node_map[independent_node]);
             independent_nodes.pop_front();
 
-            for (auto user_sp : independent_node->get_users())
+            for (auto& output : independent_node->get_outputs())
             {
-                Node* user = user_sp.get();
+                for (auto& input : output.get_inputs())
+                {
+                    auto user = input->get_raw_pointer_node();
                     node_dependency_count[user] -= 1;
                     size_t count = node_dependency_count[user];
                     if (count == 0)
@@ -106,6 +108,7 @@ namespace ngraph
                         independent_nodes.push_back(user);
                     }
                 }
+            }
 
             if (include_control_deps)
             {