[Layer] add "subtract layer"

- added "subtract layer"
- added a "model unit test" for sub layer.

Many people gave great feedback, so I've improved the structure accordingly.
- An upper class called "OperationLayer" was added to reduce redundant code.
- Based on the number of input tensors, the behavior of "OperationLayer" has been classified into two types: unary and binary operations.

**Self evaluation:**
1. Build test:   [X]Passed [ ]Failed [ ]Skipped
2. Run test:     [X]Passed [ ]Failed [ ]Skipped

Signed-off-by: Seungbaek Hong <[email protected]>

api/ccapi/include/layer.h

@@ -35,9 +35,10 @@ namespace train {
  * @brief     Enumeration of layer type
  */
 enum LayerType {
-  LAYER_IN = ML_TRAIN_LAYER_TYPE_INPUT,      /**< Input Layer type */
-  LAYER_WEIGHT = ML_TRAIN_LAYER_TYPE_WEIGHT, /**< Weight Layer type */
-  LAYER_ADD = ML_TRAIN_LAYER_TYPE_ADD,       /**< Add Layer type */
+  LAYER_IN = ML_TRAIN_LAYER_TYPE_INPUT,          /**< Input Layer type */
+  LAYER_WEIGHT = ML_TRAIN_LAYER_TYPE_WEIGHT,     /**< Weight Layer type */
+  LAYER_ADD = ML_TRAIN_LAYER_TYPE_ADD,           /**< Add Layer type */
+  LAYER_SUBTRACT = ML_TRAIN_LAYER_TYPE_SUBTRACT, /**< Subtract Layer type */
   LAYER_FC = ML_TRAIN_LAYER_TYPE_FC,         /**< Fully Connected Layer type */
   LAYER_SWIGLU = ML_TRAIN_LAYER_TYPE_SWIGLU, /**< Swiglu Layer type */
   LAYER_BN = ML_TRAIN_LAYER_TYPE_BN, /**< Batch Normalization Layer type */
@@ -314,6 +315,14 @@ AddLayer(const std::vector<std::string> &properties = {}) {
   return createLayer(LayerType::LAYER_ADD, properties);
 }
 
+/**
+ * @brief Helper function to create subtract layer
+ */
+inline std::unique_ptr<Layer>
+SubtractLayer(const std::vector<std::string> &properties = {}) {
+  return createLayer(LayerType::LAYER_SUBTRACT, properties);
+}
+
 /**
  * @brief Helper function to create fully connected layer
  */

api/nntrainer-api-common.h

@@ -66,6 +66,7 @@ typedef enum {
   ML_TRAIN_LAYER_TYPE_SWIGLU = 30,   /**< Swiglu Layer type */
   ML_TRAIN_LAYER_TYPE_WEIGHT = 31,   /**< Weight Layer type (Since 9.0)*/
   ML_TRAIN_LAYER_TYPE_ADD = 32,      /**< Add Layer type (Since 9.0)*/
+  ML_TRAIN_LAYER_TYPE_SUBTRACT = 33, /**< Subtract Layer type (Since 9.0)*/
   ML_TRAIN_LAYER_TYPE_PREPROCESS_FLIP =
     300, /**< Preprocess flip Layer (Since 6.5) */
   ML_TRAIN_LAYER_TYPE_PREPROCESS_TRANSLATE =

nntrainer/app_context.cpp

@@ -74,6 +74,7 @@
 #include <rnn.h>
 #include <rnncell.h>
 #include <split_layer.h>
+#include <subtract_layer.h>
 #include <time_dist.h>
 #include <upsample2d_layer.h>
 #include <weight_layer.h>
@@ -256,6 +257,8 @@ static void add_default_object(AppContext &ac) {
                      LayerType::LAYER_WEIGHT);
   ac.registerFactory(nntrainer::createLayer<AddLayer>, AddLayer::type,
                      LayerType::LAYER_ADD);
+  ac.registerFactory(nntrainer::createLayer<SubtractLayer>, SubtractLayer::type,
+                     LayerType::LAYER_SUBTRACT);
   ac.registerFactory(nntrainer::createLayer<FullyConnectedLayer>,
                      FullyConnectedLayer::type, LayerType::LAYER_FC);
   ac.registerFactory(nntrainer::createLayer<BatchNormalizationLayer>,

nntrainer/layers/meson.build

@@ -6,6 +6,7 @@ layer_sources = [
   'activation_layer.cpp',
   'weight_layer.cpp',
   'add_layer.cpp',
+  'subtract_layer.cpp',
   'addition_layer.cpp',
   'attention_layer.cpp',
   'mol_attention_layer.cpp',

nntrainer/layers/subtract_layer.cpp

@@ -0,0 +1,49 @@
+// SPDX-License-Identifier: Apache-2.0
+/**
+ * Copyright (C) 2024 SeungBaek Hong <[email protected]>
+ *
+ * @file   subtract_layer.cpp
+ * @date   10 Oct 2024
+ * @see    https://github.com/nnstreamer/nntrainer
+ * @author SeungBaek Hong <[email protected]>
+ * @bug    No known bugs except for NYI items
+ * @brief  This is subtract layer class (operation layer)
+ *
+ */
+
+#include <nntrainer_error.h>
+#include <nntrainer_log.h>
+#include <node_exporter.h>
+#include <subtract_layer.h>
+#include <util_func.h>
+
+#include <layer_context.h>
+
+namespace nntrainer {
+
+void SubtractLayer::finalize(InitLayerContext &context) {
+  context.setOutputDimensions({context.getInputDimensions()[0]});
+}
+
+void SubtractLayer::forwarding_operation(const Tensor &input0,
+                                         const Tensor &input1, Tensor &hidden) {
+  input0.subtract(input1, hidden);
+}
+
+void SubtractLayer::calcDerivative(RunLayerContext &context) {
+  context.getOutgoingDerivative(0).copy(
+    context.getIncomingDerivative(SINGLE_INOUT_IDX));
+
+  context.getOutgoingDerivative(1).copy(
+    context.getIncomingDerivative(SINGLE_INOUT_IDX).multiply(-1));
+}
+
+void SubtractLayer::setProperty(const std::vector<std::string> &values) {
+  auto remain_props = loadProperties(values, subtract_props);
+  if (!remain_props.empty()) {
+    std::string msg = "[SubtractLayer] Unknown Layer Properties count " +
+                      std::to_string(values.size());
+    throw exception::not_supported(msg);
+  }
+}
+} /* namespace nntrainer */

nntrainer/layers/subtract_layer.h

@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: Apache-2.0
+/**
+ * Copyright (C) 2024 SeungBaek Hong <[email protected]>
+ *
+ * @file   subtract_layer.h
+ * @date   10 Oct 2024
+ * @see    https://github.com/nnstreamer/nntrainer
+ * @author SeungBaek Hong <[email protected]>
+ * @bug    No known bugs except for NYI items
+ * @brief  This is subtract layer class (operation layer)
+ *
+ */
+
+#ifndef __SUBTRACT_LAYER_H__
+#define __SUBTRACT_LAYER_H__
+#ifdef __cplusplus
+
+#include <common_properties.h>
+#include <layer_devel.h>
+#include <operation_layer.h>
+
+namespace nntrainer {
+
+/**
+ * @class Subtract Layer
+ * @brief Subtract Layer
+ */
+class SubtractLayer : public BinaryOperationLayer {
+public:
+  /**
+   * @brief Constructor of Subtract Layer
+   */
+  SubtractLayer() : BinaryOperationLayer(), subtract_props(props::Print()) {}
+
+  /**
+   * @brief Destructor of Sub Layer
+   */
+  ~SubtractLayer(){};
+
+  /**
+   *  @brief  Move constructor of Sub Layer.
+   *  @param[in] SubtractLayer &&
+   */
+  SubtractLayer(SubtractLayer &&rhs) noexcept = default;
+
+  /**
+   * @brief  Move assignment operator.
+   * @parma[in] rhs SubtractLayer to be moved.
+   */
+  SubtractLayer &operator=(SubtractLayer &&rhs) = default;
+
+  /**
+   * @copydoc Layer::finalize(InitLayerContext &context)
+   */
+  void finalize(InitLayerContext &context) final;
+
+  /**
+   * @brief forwarding operation for add
+   *
+   * @param input0 input tensor 0
+   * @param input1 input tensor 1
+   * @param hidden tensor to store the result of addition
+   */
+  void forwarding_operation(const Tensor &input0, const Tensor &input1,
+                            Tensor &hidden) final;
+
+  /**
+   * @copydoc Layer::calcDerivative(RunLayerContext &context)
+   */
+  void calcDerivative(RunLayerContext &context) final;
+
+  /**
+   * @copydoc bool supportBackwarding() const
+   */
+  bool supportBackwarding() const final { return true; };
+
+  /**
+   * @copydoc Layer::exportTo(Exporter &exporter, ml::train::ExportMethods
+   * method)
+   */
+  void exportTo(Exporter &exporter,
+                const ml::train::ExportMethods &method) const final {}
+
+  /**
+   * @copydoc Layer::setProperty(const std::vector<std::string> &values)
+   */
+  void setProperty(const std::vector<std::string> &values) final;
+
+  /**
+   * @copydoc Layer::getType()
+   */
+  const std::string getType() const final { return SubtractLayer::type; };
+
+  std::tuple<props::Print> subtract_props;
+
+  inline static const std::string type = "subtract";
+};
+
+} // namespace nntrainer
+
+#endif /* __cplusplus */
+#endif /* __SUBTRACT_LAYER_H__ */

test/ccapi/unittest_ccapi.cpp

@@ -67,6 +67,9 @@ TEST(ccapi_layer, construct_02_p) {
   EXPECT_NO_THROW(layer = ml::train::layer::AddLayer());
   EXPECT_EQ(layer->getType(), "add");
 
+  EXPECT_NO_THROW(layer = ml::train::layer::SubtractLayer());
+  EXPECT_EQ(layer->getType(), "subtract");
+
   EXPECT_NO_THROW(layer = ml::train::layer::FullyConnected());
   EXPECT_EQ(layer->getType(), "fully_connected");