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#include <algorithm>
#include <cmath>
#include <vector>
#include "caffe/layer.hpp"
#include "caffe/vision_layers.hpp"
namespace caffe {
template <typename Dtype>
__global__ void SigmoidForward(const int n, const Dtype* in, Dtype* out) {
CUDA_KERNEL_LOOP(index, n) {
out[index] = 1. / (1. + exp(-in[index]));
}
}
template <typename Dtype>
void SigmoidLayer<Dtype>::Forward_gpu(const vector<Blob<Dtype>*>& bottom,
const vector<Blob<Dtype>*>& top) {
const Dtype* bottom_data = bottom[0]->gpu_data();
Dtype* top_data = top[0]->mutable_gpu_data();
const int count = bottom[0]->count();
// NOLINT_NEXT_LINE(whitespace/operators)
SigmoidForward<Dtype><<<CAFFE_GET_BLOCKS(count), CAFFE_CUDA_NUM_THREADS>>>(
count, bottom_data, top_data);
CUDA_POST_KERNEL_CHECK;
// << " count: " << count << " bottom_data: "
// << (unsigned long)bottom_data
// << " top_data: " << (unsigned long)top_data
// << " blocks: " << CAFFE_GET_BLOCKS(count)
// << " threads: " << CAFFE_CUDA_NUM_THREADS;
}
template <typename Dtype>
__global__ void SigmoidBackward(const int n, const Dtype* in_diff,
const Dtype* out_data, Dtype* out_diff) {
CUDA_KERNEL_LOOP(index, n) {
const Dtype sigmoid_x = out_data[index];
out_diff[index] = in_diff[index] * sigmoid_x * (1 - sigmoid_x);
}
}
template <typename Dtype>
void SigmoidLayer<Dtype>::Backward_gpu(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]->gpu_data();
const Dtype* top_diff = top[0]->gpu_diff();
Dtype* bottom_diff = bottom[0]->mutable_gpu_diff();
const int count = bottom[0]->count();
// NOLINT_NEXT_LINE(whitespace/operators)
SigmoidBackward<Dtype><<<CAFFE_GET_BLOCKS(count), CAFFE_CUDA_NUM_THREADS>>>(
count, top_diff, top_data, bottom_diff);
CUDA_POST_KERNEL_CHECK;
}
}
INSTANTIATE_LAYER_GPU_FUNCS(SigmoidLayer);
} // namespace caffe
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