layer.h

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#ifndef SINGA_MODEL_LAYER_H_
#define SINGA_MODEL_LAYER_H_

#include <vector>
#include <string>
#include <stack>
#include <utility>
#include <memory>
#include "singa/core/tensor.h"
#include "singa/proto/model.pb.h"
#include "singa/utils/factory.h"

namespace singa {

typedef vector<size_t> Shape;
class Layer {
 public:
  Layer() = default;

  void Setup(const Shape& in_shape, const string& proto_str) {
    LayerConf conf;
    conf.ParseFromString(proto_str);
    this->Setup(in_shape, conf);
  }

  void Setup(const vector<Shape>& in_shapes, const string& proto_str) {
    LayerConf conf;
    conf.ParseFromString(proto_str);
    this->Setup(in_shapes, conf);
  }


  // ============= Following Functions could be override =====================
  virtual ~Layer() {};

  virtual const std::string layer_type() const { return "Unknown"; }

  virtual void Setup(const Shape& in_sample, const LayerConf& conf) {
    name_ = conf.name();
    // TODO(wangwei) load param values from checkpoint files.
  }

  virtual void Setup(const vector<Shape>& in_samples, const LayerConf& conf) {
    name_ = conf.name();
    // TODO(wangwei) load param values from checkpoint files.
  }

  virtual const Shape GetOutputSampleShape() const {
    LOG(FATAL) << "Pls override this function";
    return vector<size_t>{};
  }
  virtual const Shape GetOutputSampleShape(int k) {
    LOG(FATAL) << "Pls override this function";
    return vector<size_t>{};
  }

  virtual const Tensor Forward(int flag, const Tensor& input) {
    LOG(FATAL) << "Not implemented";
    Tensor t;
    return t;
  }

  virtual const vector<Tensor> Forward(int flag, const vector<Tensor>& inputs) {
    vector<Tensor> ret;
    if (inputs.size() == 1) ret.push_back(Forward(flag, inputs.at(0)));

    LOG(FATAL) << "Not implemented";
    return ret;
  }

  // layer has no parameters.
  virtual const std::pair<Tensor, vector<Tensor>> Backward(int flag,
                                                           const Tensor& grad) {
    LOG(FATAL) << "Not implemented!";
    Tensor t;
    return std::make_pair(t, vector<Tensor>{});
  }

  virtual const std::pair<vector<Tensor>, vector<Tensor>> Backward(
      int flag, const vector<Tensor>& grads) {
    vector<Tensor> input_grad, param_grad;
    if (grads.size() == 1u) {
      auto ret = Backward(flag, grads.at(0));
      input_grad.push_back(ret.first);
      param_grad = ret.second;
    } else {
      LOG(FATAL) << "Not implemented";
    }
    return std::make_pair(input_grad, param_grad);
  }

  // virtual Layer* Clone(std::shared_ptr<Device> device);
  virtual void ToDevice(std::shared_ptr<Device> device) {
  }

  virtual void AsType(DataType dtype) {
  }

  virtual void ToProto(LayerConf* conf) const {
    //conf->set_name(name_);
    //for (const auto& spec : param_specs_) {
    //  ParamSpec* p = conf->add_param();
    //  p->CopyFrom(spec);
    //}
    // TODO(wangwei) add param values into conf;
  }

  // ========================================================================

  std::string ToProtoStr() const {
    LayerConf conf;
    ToProto(&conf);
    string str;
    conf.SerializeToString(&str);
    return str;
  }
  const vector<ParamSpec> param_specs() { return param_specs_; }

  const ParamSpec& param_specs(size_t i) {
    CHECK_LT(i, param_specs_.size());
    return param_specs_.at(i);
  }

  virtual const vector<Tensor> param_values() {
    return vector<Tensor>{};
  }

  const vector<string> param_names() {
    vector<string> pname;
    for (const auto& spec : param_specs_) pname.push_back(spec.name());
    return pname;
  }

  const string& param_name(size_t i) {
    CHECK_LT(i, param_specs_.size());
    return param_specs_.at(i).name();
  }

  const std::string name() const { return name_; }

 protected:
  std::string name_;
  vector<ParamSpec> param_specs_;
};

#define RegisterLayerClass(Name, SubLayer) \
  static Registra<Layer, SubLayer> Name##SubLayer(#Name);

inline std::shared_ptr<Layer> CreateLayer(const std::string type) {
  std::shared_ptr<Layer> layer(Factory<Layer>::Create(type));
  return layer;
}

inline const std::vector<std::string> GetRegisteredLayers() {
  vector<std::string> ret;
  for (const string type : Factory<Layer>::GetIDs()) {
    auto layer = CreateLayer(type);
    ret.push_back("Register type: " + type);
  }
  return ret;
}
}  // namespace singa
#endif  // SINGA_MODEL_LAYER_H_