[ONNX] remove dangling Parameters from graph (#3774)

We have models with inputs with no initializer and not connected to any other node.

ngraph/frontend/onnx_import/include/onnx_import/core/graph_cache.hpp

@@ -43,12 +43,17 @@ namespace ngraph
         public:
             /// \brief      Add node to the cache or override the existing one.
             ///
-            /// \note       GraphCahce takes ownership of the node.
+            /// \note       GraphCache takes ownership of the node.
             ///
             /// \param[in]  name       The name of node added to the cache.
             /// \param[in]  node       The node added to the cache.
             void emplace_node(const std::string& name, Output<ngraph::Node>&& node);
 
+            /// \brief      Remove node from the cache
+            ///
+            /// \param[in]  name       The name of node to be removed
+            void remove_node(const std::string& name);
+
             /// \brief      Get the node from the cache
             ///
             /// \note       If the node is not found the ngraph_error exception is thrown.

ngraph/frontend/onnx_import/src/core/graph.cpp

@@ -66,6 +66,25 @@ namespace ngraph
         Graph::Graph(const ONNX_NAMESPACE::GraphProto& graph_proto, Model& model)
             : Graph(graph_proto, model, std::unique_ptr<GraphCache>(new GraphCache()))
         {
+            // Remove dangling Parameters
+            for (auto param_it = m_parameters.begin(); param_it != m_parameters.end();)
+            {
+                if ((*param_it)->get_output_target_inputs(0).size() == 0)
+                {
+                    const auto& name = (*param_it)->get_friendly_name();
+                    auto out_it = std::find_if(
+                        m_outputs.begin(), m_outputs.end(), [&name](const ValueInfo& info) {
+                            return info.get_name() == name;
+                        });
+                    if (out_it == m_outputs.end())
+                    {
+                        m_cache->remove_node(name);
+                        param_it = m_parameters.erase(param_it);
+                        continue;
+                    }
+                }
+                param_it++;
+            }
         }
 
         Graph::Graph(const ONNX_NAMESPACE::GraphProto& graph_proto,

ngraph/frontend/onnx_import/src/core/graph_cache.cpp

@@ -26,6 +26,15 @@ namespace ngraph
             m_graph_cache_map[name] = std::move(node);
         }
 
+        void GraphCache::remove_node(const std::string& name)
+        {
+            auto it = m_graph_cache_map.find(name);
+            if (it != m_graph_cache_map.end())
+            {
+                m_graph_cache_map.erase(it);
+            }
+        }
+
         Output<ngraph::Node> GraphCache::get_node(const std::string& name) const
         {
             try

ngraph/test/models/onnx/dangling_parameter.prototxt

@@ -0,0 +1,53 @@
+ir_version: 4
+producer_name: "pytorch"
+producer_version: "1.2"
+graph {
+  node {
+    input: "X"
+    output: "Y"
+    op_type: "Abs"
+  }
+  name: "torch-jit-export"
+  input {
+    name: "X"
+    type {
+      tensor_type {
+        elem_type: 1
+        shape {
+          dim {
+            dim_value: 3
+          }
+        }
+      }
+    }
+  }
+  input {
+    name: "unused_bool"
+    type {
+      tensor_type {
+        elem_type: 9
+        shape {
+          dim {
+            dim_value: 1
+          }
+        }
+      }
+    }
+  }
+  output {
+    name: "Y"
+    type {
+      tensor_type {
+        elem_type: 1
+        shape {
+          dim {
+            dim_value: 3
+          }
+        }
+      }
+    }
+  }
+}
+opset_import {
+  version: 9
+}

ngraph/test/onnx/onnx_import.in.cpp

@@ -765,7 +765,6 @@ NGRAPH_TEST(${BACKEND_NAME}, onnx_model_softmax_0D)
         file_util::path_join(SERIALIZED_ZOO, "onnx/softmax_0D.prototxt"));
 
     auto test_case = test::TestCase<TestEngine>(function);
-    test_case.add_input<float>({3.141592});
     test_case.add_expected_output<float>({1.0});
     test_case.run();
 }
@@ -2597,7 +2596,6 @@ NGRAPH_TEST(${BACKEND_NAME}, onnx_model_eye_like)
         file_util::path_join(SERIALIZED_ZOO, "onnx/eye_like.prototxt"));
 
     auto test_case = test::TestCase<TestEngine>(function);
-    test_case.add_input<float>({0.f, 0.f, 0.f, 0.f, 0.f, 0.f, 0.f, 0.f, 0.f, 0.f, 0.f, 0.f});
     test_case.add_expected_output<float>(
         Shape{3, 4}, {0.f, 0.f, 0.f, 0.f, 1.f, 0.f, 0.f, 0.f, 0.f, 1.f, 0.f, 0.f});
 
@@ -3287,3 +3285,15 @@ NGRAPH_TEST(${BACKEND_NAME}, onnx_model_hard_sigmoid)
     test_case.add_expected_output<float>(Shape{4}, {1.0f, 0.0f, 0.5f, 0.699999988079071f});
     test_case.run();
 }
+
+NGRAPH_TEST(${BACKEND_NAME}, onnx_model_dangling_parameter)
+{
+    auto function = onnx_import::import_onnx_model(
+        file_util::path_join(SERIALIZED_ZOO, "onnx/dangling_parameter.prototxt"));
+
+    auto test_case = test::TestCase<TestEngine>(function);
+
+    test_case.add_input<float>({-1.0f, 2.0f, -3.0f});
+    test_case.add_expected_output<float>(Shape{3}, {1.0f, 2.0f, 3.0f});
+    test_case.run();
+}