/*
All modification made by Intel Corporation: © 2016 Intel Corporation

All contributions by the University of California:
Copyright (c) 2014, 2015, The Regents of the University of California (Regents)
All rights reserved.

All other contributions:
Copyright (c) 2014, 2015, the respective contributors
All rights reserved.
For the list of contributors go to https://github.com/BVLC/caffe/blob/master/CONTRIBUTORS.md


Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

    * Redistributions of source code must retain the above copyright notice,
      this list of conditions and the following disclaimer.
    * Redistributions in binary form must reproduce the above copyright
      notice, this list of conditions and the following disclaimer in the
      documentation and/or other materials provided with the distribution.
    * Neither the name of Intel Corporation nor the names of its contributors
      may be used to endorse or promote products derived from this software
      without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

#ifndef CAFFE_FILTER_LAYER_HPP_
#define CAFFE_FILTER_LAYER_HPP_

#include <vector>

#include "caffe/blob.hpp"
#include "caffe/layer.hpp"
#include "caffe/proto/caffe.pb.h"

namespace caffe {

/**
 * @brief Takes two+ Blobs, interprets last Blob as a selector and
 *  filter remaining Blobs accordingly with selector data (0 means that
 * the corresponding item has to be filtered, non-zero means that corresponding
 * item needs to stay).
 */
template <typename Dtype>
class FilterLayer : public Layer<Dtype> {
 public:
  explicit FilterLayer(const LayerParameter& param)
      : Layer<Dtype>(param) {}
  virtual void LayerSetUp(const vector<Blob<Dtype>*>& bottom,
      const vector<Blob<Dtype>*>& top);
  virtual void Reshape(const vector<Blob<Dtype>*>& bottom,
      const vector<Blob<Dtype>*>& top);

  virtual inline const char* type() const { return "Filter"; }
  virtual inline int MinBottomBlobs() const { return 2; }
  virtual inline int MinTopBlobs() const { return 1; }

 protected:
  /**
   * @param bottom input Blob vector (length 2+)
   *   -# @f$ (N \times C \times H \times W) @f$
   *      the inputs to be filtered @f$ x_1 @f$
   *   -# ...
   *   -# @f$ (N \times C \times H \times W) @f$
   *      the inputs to be filtered @f$ x_K @f$
   *   -# @f$ (N \times 1 \times 1 \times 1) @f$
   *      the selector blob
   * @param top output Blob vector (length 1+)
   *   -# @f$ (S \times C \times H \times W) @f$ ()
   *        the filtered output @f$ x_1 @f$
   *        where S is the number of items
   *        that haven't been filtered
   *      @f$ (S \times C \times H \times W) @f$
   *        the filtered output @f$ x_K @f$
   *        where S is the number of items
   *        that haven't been filtered
   */
  virtual void Forward_cpu(const vector<Blob<Dtype>*>& bottom,
      const vector<Blob<Dtype>*>& top);
  virtual void Forward_gpu(const vector<Blob<Dtype>*>& bottom,
    const vector<Blob<Dtype>*>& top);

  /**
   * @brief Computes the error gradient w.r.t. the forwarded inputs.
   *
   * @param top output Blob vector (length 1+), providing the error gradient with
   *        respect to the outputs
   * @param propagate_down see Layer::Backward.
   * @param bottom input Blob vector (length 2+), into which the top error
   *        gradient is copied
   */
  virtual void Backward_cpu(const vector<Blob<Dtype>*>& top,
      const vector<bool>& propagate_down, const vector<Blob<Dtype>*>& bottom);
  virtual void Backward_gpu(const vector<Blob<Dtype>*>& top,
    const vector<bool>& propagate_down, const vector<Blob<Dtype>*>& bottom);

  bool first_reshape_;
  vector<int> indices_to_forward_;
};

}  // namespace caffe

#endif  // CAFFE_FILTER_LAYER_HPP_
