SoftmaxLayer and SoftmaxwithLossLayer 代码解读

layer {
name: "loss"
type: "SoftmaxWithLoss"
bottom: "fc8"
bottom: "label"
top: "loss"
}

#include <algorithm>
#include <cfloat>
#include <vector>

#include "caffe/layers/softmax_loss_layer.hpp"
#include "caffe/util/math_functions.hpp"

namespace caffe {

template <typename Dtype>
void SoftmaxWithLossLayer<Dtype>::LayerSetUp(
     const vector<Blob<Dtype>*>& bottom, const vector<Blob<Dtype>*>& top) {
LossLayer<Dtype>::LayerSetUp(bottom, top);
LayerParameter softmax_param(this->layer_param_);
softmax_param.set_type("Softmax");
softmax_layer_ = LayerRegistry<Dtype>::CreateLayer(softmax_param);
softmax_bottom_vec_.clear();
softmax_bottom_vec_.push_back(bottom[0]); // 将bottom[0]存入softmax_bottom_vec_;
   softmax_top_vec_.clear();
softmax_top_vec_.push_back(&prob_);  　　// 将 prob_ 存入 softmax_top_vec_;

softmax_layer_->SetUp(softmax_bottom_vec_, softmax_top_vec_);

has_ignore_label_ =   // draw the parameter from layer
this->layer_param_.loss_param().has_ignore_label();
if (has_ignore_label_) {
ignore_label_ = this->layer_param_.loss_param().ignore_label();
}
if (!this->layer_param_.loss_param().has_normalization() &&
this->layer_param_.loss_param().has_normalize()) {
normalization_ = this->layer_param_.loss_param().normalize() ?
LossParameter_NormalizationMode_VALID :
LossParameter_NormalizationMode_BATCH_SIZE;
} else {
normalization_ = this->layer_param_.loss_param().normalization();
}
}

template <typename Dtype>
void SoftmaxWithLossLayer<Dtype>::Reshape(
const vector<Blob<Dtype>*>& bottom, const vector<Blob<Dtype>*>& top) {
LossLayer<Dtype>::Reshape(bottom, top);
softmax_layer_->Reshape(softmax_bottom_vec_, softmax_top_vec_);
softmax_axis_ =
bottom[0]->CanonicalAxisIndex(this->layer_param_.softmax_param().axis());
outer_num_ = bottom[0]->count(0, softmax_axis_);
inner_num_ = bottom[0]->count(softmax_axis_ + 1);
CHECK_EQ(outer_num_ * inner_num_, bottom[1]->count())
<< "Number of labels must match number of predictions; "
<< "e.g., if softmax axis == 1 and prediction shape is (N, C, H, W), "
<< "label count (number of labels) must be N*H*W, "
<< "with integer values in {0, 1, ..., C-1}.";
if (top.size() >= 2) {
// softmax output
top[1]->ReshapeLike(*bottom[0]);
}
}