Method Backward_cpu

src/caffe/layers/recurrent_layer.cpp:277–287

template <typename Dtype>
void RecurrentLayer<Dtype>::Backward_cpu(const vector<Blob<Dtype>*>& top,
    const vector<bool>& propagate_down, const vector<Blob<Dtype>*>& bottom) {
  CHECK(!propagate_down[1]) << "Cannot backpropagate to sequence indicators.";

  // TODO: skip backpropagation to inputs and parameters inside the unrolled
  // net according to propagate_down[0] and propagate_down[2]. For now just
  // backprop to inputs and parameters unconditionally, as either the inputs or
  // the parameters do need backward (or Net would have set
  // layer_needs_backward_[i] == false for this layer).
  unrolled_net_->BackwardFrom(last_layer_index_);
}

#ifdef CPU_ONLY
STUB_GPU_FORWARD(RecurrentLayer, Forward);