BVLC · Yangqing · Nov 28, 2013 · Nov 28, 2013
diff --git a/include/caffe/vision_layers.hpp b/include/caffe/vision_layers.hpp
@@ -89,6 +89,27 @@ class DropoutLayer : public NeuronLayer<Dtype> {
 };
 
 
+template <typename Dtype>
+class FlattenLayer : public Layer<Dtype> {
+ public:
+  explicit FlattenLayer(const LayerParameter& param)
+      : Layer<Dtype>(param) {}
+  virtual void SetUp(const vector<Blob<Dtype>*>& bottom,
+      vector<Blob<Dtype>*>* top);
+
+ protected:
+  virtual void Forward_cpu(const vector<Blob<Dtype>*>& bottom,
+      vector<Blob<Dtype>*>* top);
+  virtual void Forward_gpu(const vector<Blob<Dtype>*>& bottom,
+      vector<Blob<Dtype>*>* top);
+  virtual Dtype Backward_cpu(const vector<Blob<Dtype>*>& top,
+      const bool propagate_down, vector<Blob<Dtype>*>* bottom);
+  virtual Dtype Backward_gpu(const vector<Blob<Dtype>*>& top,
+      const bool propagate_down, vector<Blob<Dtype>*>* bottom);
+  int channels_out_;
+};
+
+
 template <typename Dtype>
 class InnerProductLayer : public Layer<Dtype> {
  public:

diff --git a/src/caffe/layer_factory.cpp b/src/caffe/layer_factory.cpp
@@ -31,6 +31,8 @@ Layer<Dtype>* GetLayer(const LayerParameter& param) {
     return new DropoutLayer<Dtype>(param);
   } else if (type == "euclidean_loss") {
     return new EuclideanLossLayer<Dtype>(param);
+  } else if (type == "flatten") {
+    return new FlattenLayer<Dtype>(param);
   } else if (type == "im2col") {
     return new Im2colLayer<Dtype>(param);
   } else if (type == "infogain_loss") {

diff --git a/src/caffe/layers/flatten_layer.cpp b/src/caffe/layers/flatten_layer.cpp
@@ -0,0 +1,57 @@
+// Copyright 2013 Yangqing Jia
+
+#include <vector>
+
+#include "caffe/layer.hpp"
+#include "caffe/vision_layers.hpp"
+#include "caffe/util/math_functions.hpp"
+
+namespace caffe {
+
+template <typename Dtype>
+void FlattenLayer<Dtype>::SetUp(const vector<Blob<Dtype>*>& bottom,
+      vector<Blob<Dtype>*>* top) {
+  CHECK_EQ(bottom.size(), 1) << "Flatten Layer takes a single blob as input.";
+  CHECK_EQ(top->size(), 1) << "Flatten Layer takes a single blob as output.";
+  channels_out_ = bottom[0]->channels() * bottom[0]->height()
+      * bottom[0]->width();
+  (*top)[0]->Reshape(bottom[0]->num(), channels_out_, 1, 1);
+};
+
+template <typename Dtype>
+void FlattenLayer<Dtype>::Forward_cpu(const vector<Blob<Dtype>*>& bottom,
+      vector<Blob<Dtype>*>* top) {
+
+  const Dtype* bottom_data = bottom[0]->cpu_data();
+  Dtype* top_data = (*top)[0]->mutable_cpu_data();
+  caffe_copy(channels_out_, bottom_data, top_data);
+}
+
+template <typename Dtype>
+void FlattenLayer<Dtype>::Forward_gpu(const vector<Blob<Dtype>*>& bottom,
+      vector<Blob<Dtype>*>* top) {
+  const Dtype* bottom_data = bottom[0]->gpu_data();
+  Dtype* top_data = (*top)[0]->mutable_gpu_data();
+  caffe_gpu_copy(channels_out_, bottom_data, top_data);
+}
+
+template <typename Dtype>
+Dtype FlattenLayer<Dtype>::Backward_cpu(const vector<Blob<Dtype>*>& top,
+      const bool propagate_down, vector<Blob<Dtype>*>* bottom) {
+  const Dtype* top_diff = top[0]->cpu_diff();
+  Dtype* bottom_diff = (*bottom)[0]->mutable_cpu_diff();
+  caffe_copy(channels_out_, top_diff, bottom_diff);
+}
+
+
+template <typename Dtype>
+Dtype FlattenLayer<Dtype>::Backward_gpu(const vector<Blob<Dtype>*>& top,
+      const bool propagate_down, vector<Blob<Dtype>*>* bottom) {
+  const Dtype* top_diff = top[0]->gpu_diff();
+  Dtype* bottom_diff = (*bottom)[0]->mutable_gpu_diff();
+  caffe_gpu_copy(channels_out_, top_diff, bottom_diff);
+}
+
+INSTANTIATE_CLASS(FlattenLayer);
+
+}  // namespace caffe
diff --git a/src/caffe/test/test_flatten_layer.cpp b/src/caffe/test/test_flatten_layer.cpp
@@ -0,0 +1,93 @@
+// Copyright 2013 Yangqing Jia
+
+#include <cstring>
+#include <cuda_runtime.h>
+
+#include "gtest/gtest.h"
+#include "caffe/blob.hpp"
+#include "caffe/common.hpp"
+#include "caffe/filler.hpp"
+#include "caffe/vision_layers.hpp"
+#include "caffe/test/test_gradient_check_util.hpp"
+
+#include "caffe/test/test_caffe_main.hpp"
+
+namespace caffe {
+
+extern cudaDeviceProp CAFFE_TEST_CUDA_PROP;
+
+template <typename Dtype>
+class FlattenLayerTest : public ::testing::Test {
+ protected:
+  FlattenLayerTest()
+      : blob_bottom_(new Blob<Dtype>(2, 3, 6, 5)),
+        blob_top_(new Blob<Dtype>()) {
+    // fill the values
+    FillerParameter filler_param;
+    GaussianFiller<Dtype> filler(filler_param);
+    filler.Fill(this->blob_bottom_);
+    blob_bottom_vec_.push_back(blob_bottom_);
+    blob_top_vec_.push_back(blob_top_);
+  };
+  virtual ~FlattenLayerTest() { delete blob_bottom_; delete blob_top_; }
+  Blob<Dtype>* const blob_bottom_;
+  Blob<Dtype>* const blob_top_;
+  vector<Blob<Dtype>*> blob_bottom_vec_;
+  vector<Blob<Dtype>*> blob_top_vec_;
+};
+
+typedef ::testing::Types<float, double> Dtypes;
+TYPED_TEST_CASE(FlattenLayerTest, Dtypes);
+
+TYPED_TEST(FlattenLayerTest, TestSetup) {
+  LayerParameter layer_param;
+  FlattenLayer<TypeParam> layer(layer_param);
+  layer.SetUp(this->blob_bottom_vec_, &(this->blob_top_vec_));
+  EXPECT_EQ(this->blob_top_->num(), 2);
+  EXPECT_EQ(this->blob_top_->channels(), 3 * 6 * 5);
+  EXPECT_EQ(this->blob_top_->height(), 1);
+  EXPECT_EQ(this->blob_top_->width(), 1);
+}
+
+TYPED_TEST(FlattenLayerTest, TestCPU) {
+  LayerParameter layer_param;
+  FlattenLayer<TypeParam> layer(layer_param);
+  Caffe::set_mode(Caffe::CPU);
+  layer.SetUp(this->blob_bottom_vec_, &(this->blob_top_vec_));
+  layer.Forward(this->blob_bottom_vec_, &(this->blob_top_vec_));
+  for (int c = 0; c < 3 * 6 * 5; ++c) {
+    EXPECT_EQ(this->blob_top_->data_at(0, c, 0, 0),
+        this->blob_bottom_->data_at(0, c / (6 * 5), (c / 5) % 6, c % 5));
+  }
+}
+
+TYPED_TEST(FlattenLayerTest, TestGPU) {
+  LayerParameter layer_param;
+  FlattenLayer<TypeParam> layer(layer_param);
+  Caffe::set_mode(Caffe::GPU);
+  layer.SetUp(this->blob_bottom_vec_, &(this->blob_top_vec_));
+  layer.Forward(this->blob_bottom_vec_, &(this->blob_top_vec_));
+  for (int c = 0; c < 3 * 6 * 5; ++c) {
+    EXPECT_EQ(this->blob_top_->data_at(0, c, 0, 0),
+        this->blob_bottom_->data_at(0, c / (6 * 5), (c / 5) % 6, c % 5));
+  }
+}
+
+TYPED_TEST(FlattenLayerTest, TestCPUGradient) {
+  LayerParameter layer_param;
+  Caffe::set_mode(Caffe::CPU);
+  FlattenLayer<TypeParam> layer(layer_param);
+  GradientChecker<TypeParam> checker(1e-2, 1e-2);
+  checker.CheckGradientExhaustive(layer, this->blob_bottom_vec_, this->blob_top_vec_);
+}
+
+TYPED_TEST(FlattenLayerTest, TestGPUGradient) {
+  LayerParameter layer_param;
+  Caffe::set_mode(Caffe::GPU);
+  FlattenLayer<TypeParam> layer(layer_param);
+  GradientChecker<TypeParam> checker(1e-2, 1e-2);
+  checker.CheckGradientExhaustive(layer, this->blob_bottom_vec_, this->blob_top_vec_);
+}
+
+
+}