Implement flatten layer (#157)

include/layers/FlattenLayer.hpp

@@ -0,0 +1,15 @@
+#pragma once
+#include <string>
+
+#include "layers/Layer.hpp"
+
+namespace itlab_2023 {
+
+class FlattenLayer : public Layer {
+ public:
+  FlattenLayer() = default;
+  static std::string get_name() { return "Flatten layer"; }
+  void run(const Tensor& input, Tensor& output) override;
+};
+
+}  // namespace itlab_2023

src/layers/FlattenLayer.cpp

@@ -0,0 +1,23 @@
+#include "layers/FlattenLayer.hpp"
+
+namespace itlab_2023 {
+
+void FlattenLayer::run(const Tensor &input, Tensor &output) {
+  switch (input.get_type()) {
+    case Type::kInt: {
+      output =
+          make_tensor(*input.as<int>(), Shape({input.get_shape().count()}));
+      break;
+    }
+    case Type::kFloat: {
+      output =
+          make_tensor(*input.as<float>(), Shape({input.get_shape().count()}));
+      break;
+    }
+    default: {
+      throw std::runtime_error("No such type");
+    }
+  }
+}
+
+}  // namespace itlab_2023

test/single_layer/test_flattenlayer.cpp

@@ -0,0 +1,30 @@
+#include <vector>
+
+#include "gtest/gtest.h"
+#include "layers/FlattenLayer.hpp"
+
+using namespace itlab_2023;
+
+TEST(flattenlayer, new_flattenlayer_can_flatten_int) {
+  FlattenLayer layer;
+  Shape sh({2, 2});
+  Tensor input = make_tensor<int>({1, -1, 2, -2}, sh);
+  Tensor output;
+  layer.run(input, output);
+  EXPECT_EQ(output.get_shape().dims(), 1);
+  EXPECT_EQ(output.get_shape()[0], 4);
+}
+
+TEST(flattenlayer, new_flattenlayer_can_flatten_float) {
+  FlattenLayer layer;
+  Shape sh({2, 2});
+  Tensor input = make_tensor<float>({1.0F, -1.0F, 2.0F, -2.0F}, sh);
+  Tensor output;
+  layer.run(input, output);
+  EXPECT_EQ(output.get_shape().dims(), 1);
+  EXPECT_EQ(output.get_shape()[0], 4);
+}
+
+TEST(flattenlayer, get_layer_name) {
+  EXPECT_EQ(FlattenLayer::get_name(), "Flatten layer");
+}