#include <vector>

#include "caffe/layer.hpp"

#include "caffe/util/math_functions.hpp"

#include "caffe/vision_layers.hpp"

namespace caffe {

template <typename Dtype>

void FilterLayer<Dtype>::Forward_gpu(const vector<Blob<Dtype>*>& bottom,

const vector<Blob<Dtype>*>& top) {

int new_tops_num = indices_to_forward_.size();

// forward all filtered items for all bottoms but the Selector (bottom[last])

for (int t = 0; t < top.size(); ++t) {

const Dtype* bottom_data = bottom[t]->gpu_data();

Dtype* top_data = top[t]->mutable_gpu_data();

int dim = bottom[t]->count() / bottom[t]->shape(0);

for (int n = 0; n < new_tops_num; ++n) {

int data_offset_top = n * dim;

int data_offset_bottom = indices_to_forward_[n] * dim;

caffe_copy(dim, bottom_data + data_offset_bottom,

top_data + data_offset_top);

}

}

}

template <typename Dtype>

void FilterLayer<Dtype>::Backward_gpu(const vector<Blob<Dtype>*>& top,

const vector<bool>& propagate_down, const vector<Blob<Dtype>*>& bottom) {

if (propagate_down[bottom.size() - 1]) {

LOG(FATAL) << this->type()

<< "Layer cannot backpropagate to filter index inputs";

}

for (int i = 0; i < top.size(); ++i) {

// bottom[last] is the selector and never needs backpropagation

// so we can iterate over top vector because top.size() == bottom.size() -1

if (propagate_down[i]) {

const int dim = top[i]->count() / top[i]->shape(0);

int next_to_backward_offset = 0;

int batch_offset = 0;

int data_offset_bottom = 0;

int data_offset_top = 0;

for (int n = 0; n < bottom[i]->shape(0); ++n) {

if (next_to_backward_offset >= indices_to_forward_.size()) {

// we already visited all items that were been forwarded, so

// just set to zero remaining ones

data_offset_bottom = n * dim;

caffe_gpu_set(dim, Dtype(0),

bottom[i]->mutable_gpu_diff() + data_offset_bottom);

} else {

batch_offset = indices_to_forward_[next_to_backward_offset];

data_offset_bottom = n * dim;

if (n != batch_offset) { // this data was not been forwarded

caffe_gpu_set(dim, Dtype(0),

bottom[i]->mutable_gpu_diff() + data_offset_bottom);

} else { // this data was been forwarded

data_offset_top = next_to_backward_offset * dim;

++next_to_backward_offset; // point to next forwarded item index

caffe_copy(dim, top[i]->mutable_gpu_diff() + data_offset_top,

bottom[i]->mutable_gpu_diff() + data_offset_bottom);

}

}

}

}

}

}

INSTANTIATE_LAYER_GPU_FUNCS(FilterLayer);

} // namespace caffe