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#include <cmath>
#include <vector>
#include "caffe/layers/sigmoid_layer.hpp"
namespace caffe {
template <typename Dtype>
inline Dtype sigmoid(Dtype x) {
return 1. / (1. + exp(-x));
}
template <typename Dtype>
void SigmoidLayer<Dtype>::Forward_cpu(const vector<Blob<Dtype>*>& bottom,
const vector<Blob<Dtype>*>& top) {
const Dtype* bottom_data = bottom[0]->cpu_data();
Dtype* top_data = top[0]->mutable_cpu_data();
const int count = bottom[0]->count();
for (int i = 0; i < count; ++i) {
top_data[i] = sigmoid(bottom_data[i]);
}
}
template <typename Dtype>
void SigmoidLayer<Dtype>::Backward_cpu(const vector<Blob<Dtype>*>& top,
const vector<bool>& propagate_down,
const vector<Blob<Dtype>*>& bottom) {
if (propagate_down[0]) {
const Dtype* top_data = top[0]->cpu_data();
const Dtype* top_diff = top[0]->cpu_diff();
Dtype* bottom_diff = bottom[0]->mutable_cpu_diff();
const int count = bottom[0]->count();
for (int i = 0; i < count; ++i) {
const Dtype sigmoid_x = top_data[i];
bottom_diff[i] = top_diff[i] * sigmoid_x * (1. - sigmoid_x);
}
}
}
#ifdef CPU_ONLY
STUB_GPU(SigmoidLayer);
#endif
INSTANTIATE_CLASS(SigmoidLayer);
} // namespace caffe
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