///////////////////////////////////////////////////////////////////////

// File:        maxpool.h

// Description: Standard Max-Pooling layer.

// Author:      Ray Smith

//

// (C) Copyright 2014, Google Inc.

// Licensed 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 TESSERACT_LSTM_MAXPOOL_H_

#define TESSERACT_LSTM_MAXPOOL_H_

#include "reconfig.h"

namespace tesseract {

// Maxpooling reduction. Independently for each input, selects the location

// in the rectangle that contains the max value.

// Backprop propagates only to the position that was the max.

class Maxpool : public Reconfig {

public:

  TESS_API

  Maxpool(const std::string &name, int ni, int x_scale, int y_scale);

  ~Maxpool() override = default;

  // Accessors.

  std::string spec() const override {

    return "Mp" + std::to_string(y_scale_) + "," + std::to_string(x_scale_);

  }

  // Reads from the given file. Returns false in case of error.

  bool DeSerialize(TFile *fp) override;

  // Runs forward propagation of activations on the input line.

  // See Network for a detailed discussion of the arguments.

  void Forward(bool debug, const NetworkIO &input, const TransposedArray *input_transpose,

               NetworkScratch *scratch, NetworkIO *output) override;

  // Runs backward propagation of errors on the deltas line.

  // See Network for a detailed discussion of the arguments.

  bool Backward(bool debug, const NetworkIO &fwd_deltas, NetworkScratch *scratch,

                NetworkIO *back_deltas) override;

private:

  // Memory of which input was the max.

  GENERIC_2D_ARRAY<int> maxes_;

};

} // namespace tesseract.

#endif // TESSERACT_LSTM_MAXPOOL_H_