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// Copyright 2014 Jeff Donahue
#include <vector>
#include "caffe/layer.hpp"
#include "caffe/vision_layers.hpp"
#include "caffe/util/math_functions.hpp"
namespace caffe {
template <typename Dtype>
void SplitLayer<Dtype>::SetUp(const vector<Blob<Dtype>*>& bottom,
vector<Blob<Dtype>*>* top) {
CHECK_EQ(bottom.size(), 1) << "Split Layer takes a single blob as input.";
CHECK_GE(top->size(), 1) << "Split Layer takes at least one blob as output.";
count_ = bottom[0]->count();
for (int i = 0; i < top->size(); ++i) {
// Allow the 0th top blob to be 'in-place', but no others.
if (i == 0 && (*top)[i] == bottom[0]) {
continue;
} else {
CHECK_NE((*top)[i], bottom[0]) << "Only 0th top blob may be in place.";
}
(*top)[i]->Reshape(bottom[0]->num(), bottom[0]->channels(),
bottom[0]->height(), bottom[0]->width());
CHECK_EQ(count_, (*top)[i]->count());
}
}
template <typename Dtype>
Dtype SplitLayer<Dtype>::Forward_cpu(const vector<Blob<Dtype>*>& bottom,
vector<Blob<Dtype>*>* top) {
const Dtype* bottom_data = bottom[0]->cpu_data();
for (int i = 0; i < top->size(); ++i) {
if (i == 0 && (*top)[i] == bottom[0]) {
continue;
}
Dtype* top_data = (*top)[i]->mutable_cpu_data();
caffe_copy(count_, bottom_data, top_data);
}
return Dtype(0.);
}
template <typename Dtype>
void SplitLayer<Dtype>::Backward_cpu(const vector<Blob<Dtype>*>& top,
const bool propagate_down, vector<Blob<Dtype>*>* bottom) {
if (propagate_down) {
const Dtype* top_diff = top[0]->cpu_diff();
Dtype* bottom_diff = (*bottom)[0]->mutable_cpu_diff();
// Initialize by copying first top blob diff to our diff, unless we're
// doing in-place computation for the first blob, in which case the diff is
// already initialized.
if (top[0] != (*bottom)[0]) {
caffe_copy(count_, top_diff, bottom_diff);
}
// Add remaining top blob diffs.
for (int i = 1; i < top.size(); ++i) {
top_diff = top[i]->cpu_diff();
caffe_axpy(count_, Dtype(1.), top_diff, bottom_diff);
}
}
}
INSTANTIATE_CLASS(SplitLayer);
} // namespace caffe
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