From 8d6b8b45b6450747146e6c9c7a11e2102903b146 Mon Sep 17 00:00:00 2001
From: Aleksandr Rybnikov <arrybn@gmail.com>
Date: Tue, 1 Aug 2017 16:58:34 +0300
Subject: [PATCH] Added ELU and test for it

---
 .../dnn/include/opencv2/dnn/all_layers.hpp    |  6 +++
 modules/dnn/src/init.cpp                      |  1 +
 modules/dnn/src/layers/elementwise_layers.cpp | 37 +++++++++++++++++++
 modules/dnn/src/tensorflow/tf_importer.cpp    |  7 ++++
 modules/dnn/test/test_layers.cpp              | 18 +++++++++
 5 files changed, 69 insertions(+)

diff --git a/modules/dnn/include/opencv2/dnn/all_layers.hpp b/modules/dnn/include/opencv2/dnn/all_layers.hpp
index 4f01227573..333656a3cf 100644
--- a/modules/dnn/include/opencv2/dnn/all_layers.hpp
+++ b/modules/dnn/include/opencv2/dnn/all_layers.hpp
@@ -349,6 +349,12 @@ CV__DNN_EXPERIMENTAL_NS_BEGIN
         static Ptr<ChannelsPReLULayer> create(const LayerParams& params);
     };
 
+    class CV_EXPORTS ELULayer : public ActivationLayer
+    {
+    public:
+        static Ptr<ELULayer> create(const LayerParams &params);
+    };
+
     class CV_EXPORTS TanHLayer : public ActivationLayer
     {
     public:
diff --git a/modules/dnn/src/init.cpp b/modules/dnn/src/init.cpp
index 97ea169f81..32ff69ecec 100644
--- a/modules/dnn/src/init.cpp
+++ b/modules/dnn/src/init.cpp
@@ -96,6 +96,7 @@ void initializeLayerFactory()
     CV_DNN_REGISTER_LAYER_CLASS(ChannelsPReLU,  ChannelsPReLULayer);
     CV_DNN_REGISTER_LAYER_CLASS(Sigmoid,        SigmoidLayer);
     CV_DNN_REGISTER_LAYER_CLASS(TanH,           TanHLayer);
+    CV_DNN_REGISTER_LAYER_CLASS(ELU,            ELULayer);
     CV_DNN_REGISTER_LAYER_CLASS(BNLL,           BNLLLayer);
     CV_DNN_REGISTER_LAYER_CLASS(AbsVal,         AbsLayer);
     CV_DNN_REGISTER_LAYER_CLASS(Power,          PowerLayer);
diff --git a/modules/dnn/src/layers/elementwise_layers.cpp b/modules/dnn/src/layers/elementwise_layers.cpp
index 95afd96580..9c929a0098 100644
--- a/modules/dnn/src/layers/elementwise_layers.cpp
+++ b/modules/dnn/src/layers/elementwise_layers.cpp
@@ -302,6 +302,35 @@ struct SigmoidFunctor
     int64 getFLOPSPerElement() const { return 3; }
 };
 
+struct ELUFunctor
+{
+    typedef ELULayer Layer;
+
+    explicit ELUFunctor() {}
+
+    void apply(const float* srcptr, float* dstptr, int len, size_t planeSize, int cn0, int cn1) const
+    {
+        for( int cn = cn0; cn < cn1; cn++, srcptr += planeSize, dstptr += planeSize )
+        {
+            for(int i = 0; i < len; i++ )
+            {
+                float x = srcptr[i];
+                dstptr[i] = x >= 0.f ? x : exp(x) - 1;
+            }
+        }
+    }
+
+#ifdef HAVE_HALIDE
+    void attachHalide(const Halide::Expr& input, Halide::Func& top)
+    {
+        Halide::Var x("x"), y("y"), c("c"), n("n");
+        top(x, y, c, n) = select(input >= 0.0f, input, exp(input) - 1);
+    }
+#endif  // HAVE_HALIDE
+
+    int64 getFLOPSPerElement() const { return 2; }
+};
+
 struct AbsValFunctor
 {
     typedef AbsLayer Layer;
@@ -504,6 +533,14 @@ Ptr<SigmoidLayer> SigmoidLayer::create(const LayerParams& params)
     return l;
 }
 
+Ptr<ELULayer> ELULayer::create(const LayerParams& params)
+{
+    Ptr<ELULayer> l(new ElementWiseLayer<ELUFunctor>(ELUFunctor()));
+    l->setParamsFrom(params);
+
+    return l;
+}
+
 Ptr<AbsLayer> AbsLayer::create(const LayerParams& params)
 {
     Ptr<AbsLayer> l(new ElementWiseLayer<AbsValFunctor>());
diff --git a/modules/dnn/src/tensorflow/tf_importer.cpp b/modules/dnn/src/tensorflow/tf_importer.cpp
index 7797fa7664..603b8367bc 100644
--- a/modules/dnn/src/tensorflow/tf_importer.cpp
+++ b/modules/dnn/src/tensorflow/tf_importer.cpp
@@ -677,6 +677,13 @@ void TFImporter::populateNet(Net dstNet)
 
             connectToAllBlobs(layer_id, dstNet, parsePin(layer.input(0)), id, layer.input_size());
         }
+        else if (type == "Elu")
+        {
+            int id = dstNet.addLayer(name, "ELU", layerParams);
+            layer_id[name] = id;
+
+            connectToAllBlobs(layer_id, dstNet, parsePin(layer.input(0)), id, layer.input_size());
+        }
         else if (type == "MaxPool")
         {
             layerParams.set("pool", "max");
diff --git a/modules/dnn/test/test_layers.cpp b/modules/dnn/test/test_layers.cpp
index 14c984f189..4ca06ef3d9 100644
--- a/modules/dnn/test/test_layers.cpp
+++ b/modules/dnn/test/test_layers.cpp
@@ -268,11 +268,29 @@ static void test_Reshape_Split_Slice_layers()
 
     normAssert(input, output);
 }
+
 TEST(Layer_Test_Reshape_Split_Slice, Accuracy)
 {
     test_Reshape_Split_Slice_layers();
 }
 
+TEST(Layer_Conv_Elu, Accuracy)
+{
+    Net net;
+    {
+        Ptr<Importer> importer = createTensorflowImporter(_tf("layer_elu_model.pb"));
+        ASSERT_TRUE(importer != NULL);
+        importer->populateNet(net);
+    }
+    Mat inp = blobFromNPY(_tf("layer_elu_in.npy"));
+    Mat ref = blobFromNPY(_tf("layer_elu_out.npy"));
+
+    net.setInput(inp, "input");
+    Mat out = net.forward();
+
+    normAssert(ref, out);
+}
+
 class Layer_LSTM_Test : public ::testing::Test
 {
 public: