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#include <algorithm>
#include <vector>
#include "caffe/layer.hpp"
#include "caffe/util/math_functions.hpp"
#include "caffe/vision_layers.hpp"
namespace caffe {
template <typename Dtype>
void PowerLayer<Dtype>::Forward_gpu(const vector<Blob<Dtype>*>& bottom,
const vector<Blob<Dtype>*>& top) {
Dtype* top_data = top[0]->mutable_gpu_data();
const int count = bottom[0]->count();
// Special case where we can ignore the input: scale or power is 0.
if (diff_scale_ == Dtype(0)) {
Dtype value = (power_ == 0) ? Dtype(1) : pow(shift_, power_);
caffe_gpu_set(count, value, top_data);
return;
}
const Dtype* bottom_data = bottom[0]->gpu_data();
caffe_copy(count, bottom_data, top_data);
if (scale_ != Dtype(1)) {
caffe_gpu_scal(count, scale_, top_data);
}
if (shift_ != Dtype(0)) {
caffe_gpu_add_scalar(count, shift_, top_data);
}
if (power_ != Dtype(1)) {
caffe_gpu_powx(count, top_data, power_, top_data);
}
}
template <typename Dtype>
void PowerLayer<Dtype>::Backward_gpu(const vector<Blob<Dtype>*>& top,
const vector<bool>& propagate_down,
const vector<Blob<Dtype>*>& bottom) {
if (propagate_down[0]) {
Dtype* bottom_diff = bottom[0]->mutable_gpu_diff();
const int count = bottom[0]->count();
const Dtype* top_diff = top[0]->gpu_diff();
if (diff_scale_ == Dtype(0) || power_ == Dtype(1)) {
caffe_gpu_set(count, diff_scale_, bottom_diff);
} else {
const Dtype* bottom_data = bottom[0]->gpu_data();
// Compute dy/dx = scale * power * (shift + scale * x)^(power - 1)
// = diff_scale * y / (shift + scale * x)
if (power_ == Dtype(2)) {
// Special case for y = (shift + scale * x)^2
// -> dy/dx = 2 * scale * (shift + scale * x)
// = diff_scale * shift + diff_scale * scale * x
caffe_gpu_axpby(count, diff_scale_ * scale_, bottom_data,
Dtype(0), bottom_diff);
if (shift_ != Dtype(0)) {
caffe_gpu_add_scalar(count, diff_scale_ * shift_, bottom_diff);
}
} else if (shift_ == Dtype(0)) {
// Special case for y = (scale * x)^power
// -> dy/dx = scale * power * (scale * x)^(power - 1)
// = scale * power * (scale * x)^power * (scale * x)^(-1)
// = power * y / x
const Dtype* top_data = top[0]->gpu_data();
caffe_gpu_div(count, top_data, bottom_data, bottom_diff);
caffe_gpu_scal(count, power_, bottom_diff);
} else {
caffe_copy(count, bottom_data, bottom_diff);
if (scale_ != Dtype(1)) {
caffe_gpu_scal(count, scale_, bottom_diff);
}
if (shift_ != Dtype(0)) {
caffe_gpu_add_scalar(count, shift_, bottom_diff);
}
const Dtype* top_data = top[0]->gpu_data();
caffe_gpu_div<Dtype>(count, top_data, bottom_diff, bottom_diff);
if (diff_scale_ != Dtype(1)) {
caffe_gpu_scal(count, diff_scale_, bottom_diff);
}
}
}
caffe_gpu_mul(count, top_diff, bottom_diff, bottom_diff);
}
}
INSTANTIATE_LAYER_GPU_FUNCS(PowerLayer);
} // namespace caffe
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