1.自定义字段
最近在老版本的caffe上跑resnext网络的时候出现如下所示的bug，正如我们上一篇文章Caffe | 核心积木Layer层类详解中说到的，在caffe.proto文件的PoolingParameter中没有ceil_mode这个field字段。因此只有在源码中添加这个参数以及相关实现代码，并重新编译caffe。
Message type “caffe.PoolingParameter” has no field named “ceil_mode”.
（1）修改pooling_layer.hpp文件
首先在头文件中添加参数的定义，因为参数在使用之前需要先定义（C/C++语言的特性）。
int height_, width_;
int pooled_height_, pooled_width_;
bool global_pooling_;
bool ceil_mode_; //添加bug中指出的缺少的属性
Blob<Dtype> rand_idx_;
Blob<int> max_idx_;
（2）修改pooling_layer.cpp文件中对应参数
也是在上一篇文章Caffe | 核心积木Layer层类详解中说到的，每一个层（包括当前存在问题的PoolingLayer）都继承自基类LayerParameter。而基类参数中有两个重要的函数如下：
- Layersetup：读取指定层类的layer param（层参数），为后续reshape做准备。
- reshape：根据输入该层的bottom blob的形状，和改成定制化的计算策略（也就是当前层的逻辑）计算得到对应的top blob的形状，并预先分配好内存空间。
所以在这里这两个函数跟参数紧密相关，因此我们主要修改的就是pooling_layer.cpp中的这两个函数。
Layersetup函数：
|| (!pool_param.has_stride_h() && !pool_param.has_stride_w()))
<< "Stride is stride OR stride_h and stride_w are required.";
global_pooling_ = pool_param.global_pooling();
// 添加的代码-----------------------------------
ceil_mode_ = pool_param.ceil_mode(); //添加的代码，
//主要作用是从参数文件中获取ceil_mode_的参数数值。
// ------------------------------------------------------
if (global_pooling_) {
kernel_h_ = bottom[0]->height();
kernel_w_ = bottom[0]->width();
if (pad_h_ != 0 || pad_w_ != 0) {
CHECK(this->layer_param_.pooling_param().pool()
== PoolingParameter_PoolMethod_AVE
|| this->layer_param_.pooling_param().pool()
== PoolingParameter_PoolMethod_MAX)
<< "Padding implemented only for average and max pooling.";
CHECK_LT(pad_h_, kernel_h_);
CHECK_LT(pad_w_, kernel_w_);
Reshape函数：
void PoolingLayer<Dtype>::Reshape(const vector<Blob<Dtype>*>& bottom,
const vector<Blob<Dtype>*>& top) {
CHECK_EQ(4, bottom[0]->num_axes()) << "Input must have 4 axes, "
<< "corresponding to (num, channels, height, width)";
channels_ = bottom[0]->channels();
height_ = bottom[0]->height();
width_ = bottom[0]->width();
if (global_pooling_) {
kernel_h_ = bottom[0]->height();
kernel_w_ = bottom[0]->width();
}
- pooled_height_ = static_cast<int>(ceil(static_cast<float>(
- height_ + 2 * pad_h_ - kernel_h_) / stride_h_)) + 1;
- pooled_width_ = static_cast<int>(ceil(static_cast<float>(
- width_ + 2 * pad_w_ - kernel_w_) / stride_w_)) + 1;
+ // Specify the structure by ceil or floor mode
+
+ // 添加的代码-----------------------------------
+ if (ceil_mode_) {
+ pooled_height_ = static_cast<int>(ceil(static_cast<float>(
+ height_ + 2 * pad_h_ - kernel_h_) / stride_h_)) + 1;
+ pooled_width_ = static_cast<int>(ceil(static_cast<float>(
+ width_ + 2 * pad_w_ - kernel_w_) / stride_w_)) + 1;
+ } else {
+ pooled_height_ = static_cast<int>(floor(static_cast<float>(
+ height_ + 2 * pad_h_ - kernel_h_) / stride_h_)) + 1;
+ pooled_width_ = static_cast<int>(floor(static_cast<float>(
+ width_ + 2 * pad_w_ - kernel_w_) / stride_w_)) + 1;
+ }
+ // ------------------------------------------------------
+
if (pad_h_ || pad_w_) {
// If we have padding, ensure that the last pooling starts strictly
// inside the image (instead of at the padding); otherwise clip the last.
（3）修改caffe.proto文件中PoolingParameter
因为所有层的参数定义都存放在caffe.proto文件中，因此修改参数后需要将新的参数添加到该文件对应的层参数中，本例中就将参数添加到PoolingParameter中。
/ If global_pooling then it will pool over the size of the bottom by doing
// kernel_h = bottom->height and kernel_w = bottom->width
optional bool global_pooling = 12 [default = false];
// 添加的代码-----------------------------------
+ // Specify floor/ceil mode
// 为pooling层添加参数，这样可以在net.prototxt文件中为pooling层设置该参数，
// 注意后面需要给其设置一个ID，同时设置一个默认值。（下面是我之前文章中提到过的ID的作用）
//Message的tag：
//每个message里面的每个field都对应一个tag，
//分别是1~15或者以上，比如required string number=1；
//这个数字就是用来在生成的二进制文件中搜索查询的标签（怪不得会快）。
//关于这个数字，1到15会花费1byte的编码空间，16到2047花费2byte。
//所以一般建议把那些频繁使用的名字的标签设为1到15之间的值～
+ optional bool ceil_mode = 13 [default = true];
// ------------------------------------------------------
}
（4）重新编译caffe
返回到caffe的根目录，使用make指令(下面几个都可以，任选一个)，即可。
make
make -j
make -j16
make -j32 // 这里j后面的数字与电脑配置有关系，可以加速编译
2.自定义新层
这里以新增一个简单的Loss层（OHEM）举例说明自定义新层的流程。简单介绍下OHEM，难例挖掘（OHEM）是指,针对模型训练过程中导致损失值很大的一些样本(即使模型很大概率分类错误的样本),重新训练它们.维护一个错误分类样本池, 把每个batch训练数据中的出错率很大的样本放入该样本池中,当积累到一个batch以后,将这些样本放回网络重新训练。这是RGB大神的策略，用于Faster Rcnn。主要就是新增3个文件，hpp/cpp/cu。主要就是修改forward_gpu(cpu)，backward_gpu(cpu)这几个函数。
（1）hpp文件
#ifndef CAFFE_SOFTMAX_WITH_LOSS_OHEM_LAYER_HPP_
#define CAFFE_SOFTMAX_WITH_LOSS_OHEM_LAYER_HPP_
#include <vector>
#include "caffe/blob.hpp"
#include "caffe/layer.hpp"
#include "caffe/proto/caffe.pb.h"
#include "caffe/layers/loss_layer.hpp"
#include "caffe/layers/softmax_layer.hpp"
namespace caffe {
/**
* @brief Computes the multinomial logistic loss for a one-of-many
* classification task, passing real-valued predictions through a
* softmax to get a probability distribution over classes.
*
* This layer should be preferred over separate
* SoftmaxLayer + MultinomialLogisticLossLayer
* as its gradient computation is more numerically stable.
* At test time, this layer can be replaced simply by a SoftmaxLayer.
*
* @param bottom input Blob vector (length 2)
* -# @f$ (N \times C \times H \times W) @f$
* the predictions @f$ x @f$, a Blob with values in
* @f$ [-\infty, +\infty] @f$ indicating the predicted score for each of
* the @f$ K = CHW @f$ classes. This layer maps these scores to a
* probability distribution over classes using the softmax function
* @f$ \hat{p}_{nk} = \exp(x_{nk}) /
* \left[\sum_{k'} \exp(x_{nk'})\right] @f$ (see SoftmaxLayer).
* -# @f$ (N \times 1 \times 1 \times 1) @f$
* the labels @f$ l @f$, an integer-valued Blob with values
* @f$ l_n \in [0, 1, 2, ..., K - 1] @f$
* indicating the correct class label among the @f$ K @f$ classes
* @param top output Blob vector (length 1)
* -# @f$ (1 \times 1 \times 1 \times 1) @f$
* the computed cross-entropy classification loss: @f$ E =
* \frac{-1}{N} \sum\limits_{n=1}^N \log(\hat{p}_{n,l_n})
* @f$, for softmax output class probabilites @f$ \hat{p} @f$
*/
template <typename Dtype>
class SoftmaxWithLossOHEMLayer : public LossLayer<Dtype> {
public:
/**
* @param param provides LossParameter loss_param, with options:
* - ignore_label (optional)
* Specify a label value that should be ignored when computing the loss.
* - normalize (optional, default true)
* If true, the loss is normalized by the number of (nonignored) labels
* present; otherwise the loss is simply summed over spatial locations.
*/
explicit SoftmaxWithLossOHEMLayer(const LayerParameter& param)
: LossLayer<Dtype>(param) {}
virtual void LayerSetUp(const vector<Blob<Dtype>*>& bottom,
const vector<Blob<Dtype>*>& top);
virtual void Reshape(const vector<Blob<Dtype>*>& bottom,
const vector<Blob<Dtype>*>& top);
virtual inline const char* type() const { return "SoftmaxWithLossOHEM"; }
virtual inline int ExactNumTopBlobs() const { return -1; }
virtual inline int MinTopBlobs() const { return 1; }
virtual inline int MaxTopBlobs() const { return 3; }
protected:
virtual void Forward_cpu(const vector<Blob<Dtype>*>& bottom,
const vector<Blob<Dtype>*>& top);
virtual void Forward_gpu(const vector<Blob<Dtype>*>& bottom,
const vector<Blob<Dtype>*>& top);
/**
* @brief Computes the softmax loss error gradient w.r.t. the predictions.
*
* Gradients cannot be computed with respect to the label inputs (bottom[1]),
* so this method ignores bottom[1] and requires !propagate_down[1], crashing
* if propagate_down[1] is set.
*
* @param top output Blob vector (length 1), providing the error gradient with
* respect to the outputs
* -# @f$ (1 \times 1 \times 1 \times 1) @f$
* This Blob's diff will simply contain the loss_weight* @f$ \lambda @f$,
* as @f$ \lambda @f$ is the coefficient of this layer's output
* @f$\ell_i@f$ in the overall Net loss
* @f$ E = \lambda_i \ell_i + \mbox{other loss terms}@f$; hence
* @f$ \frac{\partial E}{\partial \ell_i} = \lambda_i @f$.
* (*Assuming that this top Blob is not used as a bottom (input) by any
* other layer of the Net.)
* @param propagate_down see Layer::Backward.
* propagate_down[1] must be false as we can't compute gradients with
* respect to the labels.
* @param bottom input Blob vector (length 2)
* -# @f$ (N \times C \times H \times W) @f$
* the predictions @f$ x @f$; Backward computes diff
* @f$ \frac{\partial E}{\partial x} @f$
* -# @f$ (N \times 1 \times 1 \times 1) @f$
* the labels -- ignored as we can't compute their error gradients
*/
virtual void Backward_cpu(const vector<Blob<Dtype>*>& top,
const vector<bool>& propagate_down, const vector<Blob<Dtype>*>& bottom);
virtual void Backward_gpu(const vector<Blob<Dtype>*>& top,
const vector<bool>& propagate_down, const vector<Blob<Dtype>*>& bottom);
/// Read the normalization mode parameter and compute the normalizer based
/// on the blob size. If normalization_mode is VALID, the count of valid
/// outputs will be read from valid_count, unless it is -1 in which case
/// all outputs are assumed to be valid.
virtual Dtype get_normalizer(
LossParameter_NormalizationMode normalization_mode, int valid_count);
/// The internal SoftmaxLayer used to map predictions to a distribution.
shared_ptr<Layer<Dtype> > softmax_layer_;
/// prob stores the output probability predictions from the SoftmaxLayer.
Blob<Dtype> prob_;
/// bottom vector holder used in call to the underlying SoftmaxLayer::Forward
vector<Blob<Dtype>*> softmax_bottom_vec_;
/// top vector holder used in call to the underlying SoftmaxLayer::Forward
vector<Blob<Dtype>*> softmax_top_vec_;
/// Whether to ignore instances with a certain label.
bool has_ignore_label_;
/// The label indicating that an instance should be ignored.
int ignore_label_;
/// How to normalize the output loss.
LossParameter_NormalizationMode normalization_;
int softmax_axis_, outer_num_, inner_num_;
};
} // namespace caffe
#endif // CAFFE_SOFTMAX_WITH_LOSS_OHEMLAYER_HPP_
（2）cpp文件
#include <algorithm>
#include <cfloat>
#include <vector>
#include "caffe/layers/softmax_loss_ohem_layer.hpp"
#include "caffe/util/math_functions.hpp"
namespace caffe {
template <typename Dtype>
void SoftmaxWithLossOHEMLayer<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.clear_loss_weight();
softmax_param.set_type("Softmax");
softmax_layer_ = LayerRegistry<Dtype>::CreateLayer(softmax_param);
softmax_bottom_vec_.clear();
softmax_bottom_vec_.push_back(bottom[0]);
softmax_top_vec_.clear();
softmax_top_vec_.push_back(&prob_);
softmax_layer_->SetUp(softmax_bottom_vec_, softmax_top_vec_);
has_ignore_label_ =
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 SoftmaxWithLossOHEMLayer<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]);
}
}
template <typename Dtype>
Dtype SoftmaxWithLossOHEMLayer<Dtype>::get_normalizer(
LossParameter_NormalizationMode normalization_mode, int valid_count) {
Dtype normalizer;
switch (normalization_mode) {
case LossParameter_NormalizationMode_FULL:
normalizer = Dtype(outer_num_ * inner_num_);
break;
case LossParameter_NormalizationMode_VALID:
if (valid_count == -1) {
normalizer = Dtype(outer_num_ * inner_num_);
} else {
normalizer = Dtype(valid_count);
}
break;
case LossParameter_NormalizationMode_BATCH_SIZE:
normalizer = Dtype(outer_num_);
break;
case LossParameter_NormalizationMode_NONE:
normalizer = Dtype(1);
break;
default:
LOG(FATAL) << "Unknown normalization mode: "
<< LossParameter_NormalizationMode_Name(normalization_mode);
}
// Some users will have no labels for some examples in order to 'turn off' a
// particular loss in a multi-task setup. The max prevents NaNs in that case.
return std::max(Dtype(1.0), normalizer);
}
template <typename Dtype>
void SoftmaxWithLossOHEMLayer<Dtype>::Forward_cpu(
const vector<Blob<Dtype>*>& bottom, const vector<Blob<Dtype>*>& top) {
NOT_IMPLEMENTED;
}
template <typename Dtype>
void SoftmaxWithLossOHEMLayer<Dtype>::Backward_cpu(const vector<Blob<Dtype>*>& top,
const vector<bool>& propagate_down, const vector<Blob<Dtype>*>& bottom) {
NOT_IMPLEMENTED;
}
#ifdef CPU_ONLY
STUB_GPU(SoftmaxWithLossOHEMLayer);
#endif
INSTANTIATE_CLASS(SoftmaxWithLossOHEMLayer);
REGISTER_LAYER_CLASS(SoftmaxWithLossOHEM);
} // namespace caffe
（3）cu文件
#include <algorithm>
#include <cfloat>
#include <vector>
#include "caffe/layers/softmax_loss_ohem_layer.hpp"
#include "caffe/util/math_functions.hpp"
namespace caffe {
template <typename Dtype>
__global__ void SoftmaxLossForwardGPU(const int nthreads,
const Dtype* prob_data, const Dtype* label, Dtype* loss,
const int num, const int dim, const int spatial_dim,
const bool has_ignore_label_, const int ignore_label_,
Dtype* counts) {
CUDA_KERNEL_LOOP(index, nthreads) {
const int n = index / spatial_dim;
const int s = index % spatial_dim;
const int label_value = static_cast<int>(label[n * spatial_dim + s]);
if (has_ignore_label_ && label_value == ignore_label_) {
loss[index] = 0;
counts[index] = 0;
} else {
loss[index] = -log(max(prob_data[n * dim + label_value * spatial_dim + s],
Dtype(FLT_MIN)));
counts[index] = 1;
}
}
}
template <typename Dtype>
void SoftmaxWithLossOHEMLayer<Dtype>::Forward_gpu(
const vector<Blob<Dtype>*>& bottom, const vector<Blob<Dtype>*>& top) {
softmax_layer_->Forward(softmax_bottom_vec_, softmax_top_vec_);
const Dtype* prob_data = prob_.gpu_data();
const Dtype* label = bottom[1]->gpu_data();
const int dim = prob_.count() / outer_num_;
const int nthreads = outer_num_ * inner_num_;
// Since this memory is not used for anything, we use it here to avoid having
// to allocate new GPU memory to accumulate intermediate results.
Dtype* loss_data = bottom[0]->mutable_gpu_diff();
// Similarly, this memory is never used elsewhere, and thus we can use it
// to avoid having to allocate additional GPU memory.
Dtype* counts = prob_.mutable_gpu_diff();
// NOLINT_NEXT_LINE(whitespace/operators)
SoftmaxLossForwardGPU<Dtype><<<CAFFE_GET_BLOCKS(nthreads),
CAFFE_CUDA_NUM_THREADS>>>(nthreads, prob_data, label, loss_data,
outer_num_, dim, inner_num_, has_ignore_label_, ignore_label_, counts);
Dtype loss;
caffe_gpu_asum(nthreads, loss_data, &loss);
Dtype valid_count = -1;
// Only launch another CUDA kernel if we actually need the count of valid
// outputs.
if (normalization_ == LossParameter_NormalizationMode_VALID &&
has_ignore_label_) {
caffe_gpu_asum(nthreads, counts, &valid_count);
}
top[0]->mutable_cpu_data()[0] = loss / get_normalizer(normalization_,
valid_count);
if (top.size() >= 2) {
top[1]->ShareData(prob_);
}
if (top.size() >= 3){
//output per-instance loss
caffe_gpu_memcpy(top[2]->count() * sizeof(Dtype), loss_data,
top[2]->mutable_gpu_data());
}
// Clear scratch memory to prevent interfering with backward (see #6202).
caffe_gpu_set(bottom[0]->count(), Dtype(0), bottom[0]->mutable_gpu_diff());
}
template <typename Dtype>
__global__ void SoftmaxLossBackwardGPU(const int nthreads, const Dtype* top,
const Dtype* label, Dtype* bottom_diff, const int num, const int dim,
const int spatial_dim, const bool has_ignore_label_,
const int ignore_label_, Dtype* counts) {
const int channels = dim / spatial_dim;
CUDA_KERNEL_LOOP(index, nthreads) {
const int n = index / spatial_dim;
const int s = index % spatial_dim;
const int label_value = static_cast<int>(label[n * spatial_dim + s]);
if (has_ignore_label_ && label_value == ignore_label_) {
for (int c = 0; c < channels; ++c) {
bottom_diff[n * dim + c * spatial_dim + s] = 0;
}
counts[index] = 0;
} else {
bottom_diff[n * dim + label_value * spatial_dim + s] -= 1;
counts[index] = 1;
}
}
}
template <typename Dtype>
void SoftmaxWithLossOHEMLayer<Dtype>::Backward_gpu(const vector<Blob<Dtype>*>& top,
const vector<bool>& propagate_down, const vector<Blob<Dtype>*>& bottom) {
if (propagate_down[1]) {
LOG(FATAL) << this->type()
<< " Layer cannot backpropagate to label inputs.";
}
if (propagate_down[0]) {
Dtype* bottom_diff = bottom[0]->mutable_gpu_diff();
const Dtype* prob_data = prob_.gpu_data();
const Dtype* top_data = top[0]->gpu_data();
caffe_gpu_memcpy(prob_.count() * sizeof(Dtype), prob_data, bottom_diff);
const Dtype* label = bottom[1]->gpu_data();
const int dim = prob_.count() / outer_num_;
const int nthreads = outer_num_ * inner_num_;
// Since this memory is never used for anything else,
// we use to to avoid allocating new GPU memory.
Dtype* counts = prob_.mutable_gpu_diff();
// NOLINT_NEXT_LINE(whitespace/operators)
SoftmaxLossBackwardGPU<Dtype><<<CAFFE_GET_BLOCKS(nthreads),
CAFFE_CUDA_NUM_THREADS>>>(nthreads, top_data, label, bottom_diff,
outer_num_, dim, inner_num_, has_ignore_label_, ignore_label_, counts);
Dtype valid_count = -1;
// Only launch another CUDA kernel if we actually need the count of valid
// outputs.
if (normalization_ == LossParameter_NormalizationMode_VALID &&
has_ignore_label_) {
caffe_gpu_asum(nthreads, counts, &valid_count);
}
const Dtype loss_weight = top[0]->cpu_diff()[0] /
get_normalizer(normalization_, valid_count);
caffe_gpu_scal(prob_.count(), loss_weight , bottom_diff);
}
}
INSTANTIATE_LAYER_GPU_FUNCS(SoftmaxWithLossOHEMLayer);
} // namespace caffe
（4）重新编译caffe
返回到caffe的根目录，使用make指令(下面几个都可以，任选一个)，即可。
make
make -j
make -j16
make -j32 // 这里j后面的数字与电脑配置有关系，可以加速编译
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