对于blob.h文件。
先看成员变量。定义了6个保护的成员变量，包括前、后向传播的数据，新、旧形状数据（？），
数据个数及容量。
再看成员函数。包括构造函数（4个参数），reshape（改变blob形状），以及很多inline函数。
#ifndef CAFFE_BLOB_HPP_ #define CAFFE_BLOB_HPP_ #include <algorithm> #include <string> #include <vector> #include "caffe/common.hpp" #include "caffe/proto/caffe.pb.h" #include "caffe/syncedmem.hpp" const int kMaxBlobAxes = 32; namespace caffe { /** * @brief A wrapper around SyncedMemory holders serving as the basic * computational unit through which Layer%s, Net%s, and Solver%s * interact. * * TODO(dox): more thorough description. */ template <typename Dtype> class Blob { public: Blob() : data_(), diff_(), count_(0), capacity_(0) {} /// @brief Deprecated; use <code>Blob(const vector<int>& shape)</code>. explicit Blob(const int num, const int channels, const int height, const int width);//构造函数，explicit防止隐式转换 explicit Blob(const vector<int>& shape); /// @brief Deprecated; use <code>Reshape(const vector<int>& shape)</code>. void Reshape(const int num, const int channels, const int height, const int width); /** * @brief Change the dimensions of the blob, allocating new memory if * necessary. * * This function can be called both to create an initial allocation * of memory, and to adjust the dimensions of a top blob during Layer::Reshape * or Layer::Forward. When changing the size of blob, memory will only be * reallocated if sufficient memory does not already exist, and excess memory * will never be freed. * * Note that reshaping an input blob and immediately calling Net::Backward is * an error; either Net::Forward or Net::Reshape need to be called to * propagate the new input shape to higher layers. */ void Reshape(const vector<int>& shape); void Reshape(const BlobShape& shape); void ReshapeLike(const Blob& other); //输出数据维度 inline string shape_string() const { ostringstream stream; for (int i = 0; i < shape_.size(); ++i) { stream << shape_[i] << " "; } stream << "(" << count_ << ")";//数据个数 return stream.str(); } inline const vector<int>& shape() const { return shape_; } /** * @brief Returns the dimension of the index-th axis (or the negative index-th * axis from the end, if index is negative). * * @param index the axis index, which may be negative as it will be * "canonicalized" using CanonicalAxisIndex. * Dies on out of range index. */ inline int shape(int index) const { return shape_[CanonicalAxisIndex(index)]; } inline int num_axes() const { return shape_.size(); }//返回维度 inline int count() const { return count_; } /** * @brief Compute the volume of a slice; i.e., the product of dimensions * among a range of axes. * * @param start_axis The first axis to include in the slice. * * @param end_axis The first axis to exclude from the slice. */ inline int count(int start_axis, int end_axis) const { CHECK_LE(start_axis, end_axis);//判断维度的索引是否在范围内 CHECK_GE(start_axis, 0); CHECK_GE(end_axis, 0); CHECK_LE(start_axis, num_axes()); CHECK_LE(end_axis, num_axes()); int count = 1; for (int i = start_axis; i < end_axis; ++i) { count *= shape(i);//数据的所有维度相乘，即数据的个数 } return count; } /** * @brief Compute the volume of a slice spanning from a particular first * axis to the final axis. *给定的维度到最后的维度之间包含的数据 * @param start_axis The first axis to include in the slice. */ inline int count(int start_axis) const { return count(start_axis, num_axes()); } /** * @brief Returns the 'canonical' version of a (usually) user-specified axis, * allowing for negative indexing (e.g., -1 for the last axis). *支持负数索引，相当于从后往前， * @param axis_index the axis index. * If 0 <= index < num_axes(), return index. * If -num_axes <= index <= -1, return (num_axes() - (-index)), * e.g., the last axis index (num_axes() - 1) if index == -1, * the second to last if index == -2, etc. * Dies on out of range index. */ inline int CanonicalAxisIndex(int axis_index) const { CHECK_GE(axis_index, -num_axes()) << "axis " << axis_index << " out of range for " << num_axes() << "-D Blob with shape " << shape_string(); CHECK_LT(axis_index, num_axes()) << "axis " << axis_index << " out of range for " << num_axes() << "-D Blob with shape " << shape_string(); if (axis_index < 0) { return axis_index + num_axes(); } return axis_index; } /// @brief Deprecated legacy shape accessor num: use shape(0) instead. inline int num() const { return LegacyShape(0); } /// @brief Deprecated legacy shape accessor channels: use shape(1) instead. inline int channels() const { return LegacyShape(1); } /// @brief Deprecated legacy shape accessor height: use shape(2) instead. inline int height() const { return LegacyShape(2); } /// @brief Deprecated legacy shape accessor width: use shape(3) instead. inline int width() const { return LegacyShape(3); } //检查blob的维度 inline int LegacyShape(int index) const { CHECK_LE(num_axes(), 4) << "Cannot use legacy accessors on Blobs with > 4 axes."; CHECK_LT(index, 4); CHECK_GE(index, -4); if (index >= num_axes() || index < -num_axes()) { // Axis is out of range, but still in [0, 3] (or [-4, -1] for reverse // indexing) -- this special case simulates the one-padding used to fill // extraneous axes of legacy blobs. return 1; } return shape(index); } //计算一维线性偏移量？ inline int offset(const int n, const int c = 0, const int h = 0, const int w = 0) const { CHECK_GE(n, 0); CHECK_LE(n, num()); CHECK_GE(channels(), 0); CHECK_LE(c, channels()); CHECK_GE(height(), 0); CHECK_LE(h, height()); CHECK_GE(width(), 0); CHECK_LE(w, width()); return ((n * channels() + c) * height() + h) * width() + w; } //同上，参数不同 inline int offset(const vector<int>& indices) const { CHECK_LE(indices.size(), num_axes()); int offset = 0; for (int i = 0; i < num_axes(); ++i) { offset *= shape(i); if (indices.size() > i) { CHECK_GE(indices[i], 0); CHECK_LT(indices[i], shape(i)); offset += indices[i]; } } return offset; } /** * @brief Copy from a source Blob. * * @param source the Blob to copy from * @param copy_diff if false, copy the data; if true, copy the diff * @param reshape if false, require this Blob to be pre-shaped to the shape * of other (and die otherwise); if true, Reshape this Blob to other's * shape if necessary */ //复制blob，如果diff为false的话，则复制data，否则复制diff //reshape为true，改变blob的形状 void CopyFrom(const Blob<Dtype>& source, bool copy_diff = false, bool reshape = false); //获取内存下的数据（forward采用） inline Dtype data_at(const int n, const int c, const int h, const int w) const { return cpu_data()[offset(n, c, h, w)]; } //获取内存中diff数据（反向传播采用） inline Dtype diff_at(const int n, const int c, const int h, const int w) const { return cpu_diff()[offset(n, c, h, w)]; } inline Dtype data_at(const vector<int>& index) const { return cpu_data()[offset(index)]; } inline Dtype diff_at(const vector<int>& index) const { return cpu_diff()[offset(index)]; } //同步内存shared_ptr inline const shared_ptr<SyncedMemory>& data() const { CHECK(data_); return data_; } inline const shared_ptr<SyncedMemory>& diff() const { CHECK(diff_); return diff_; } //属性 const Dtype* cpu_data() const; void set_cpu_data(Dtype* data); const int* gpu_shape() const; const Dtype* gpu_data() const; void set_gpu_data(Dtype* data); const Dtype* cpu_diff() const; const Dtype* gpu_diff() const; Dtype* mutable_cpu_data(); Dtype* mutable_gpu_data(); Dtype* mutable_cpu_diff(); Dtype* mutable_gpu_diff(); //计算 void Update(); //从protobuf序列化文件中读取blob对象 void FromProto(const BlobProto& proto, bool reshape = true); //将对象序列化为protobuf中 void ToProto(BlobProto* proto, bool write_diff = false) const; //计算绝对值 /// @brief Compute the sum of absolute values (L1 norm) of the data. Dtype asum_data() const; /// @brief Compute the sum of absolute values (L1 norm) of the diff. Dtype asum_diff() const; //计算平方和 /// @brief Compute the sum of squares (L2 norm squared) of the data. Dtype sumsq_data() const; /// @brief Compute the sum of squares (L2 norm squared) of the diff. Dtype sumsq_diff() const; // /// @brief Scale the blob data by a constant factor. void scale_data(Dtype scale_factor); /// @brief Scale the blob diff by a constant factor. void scale_diff(Dtype scale_factor); /** * @brief Set the data_ shared_ptr to point to the SyncedMemory holding the * data_ of Blob other -- useful in Layer%s which simply perform a copy * in their Forward pass. *将别的blob的data和diff指针给这个blob，实现数据的共享 同时注意到的是，这个操作会引起这个blob里面的syncedmemory被释放， 因为shared_ptr被用=重置的时候，会调用其析构器？ 在前向传递中，对简单的复制比较有用 * This deallocates the SyncedMemory holding this Blob's data_, as * shared_ptr calls its destructor when reset with the "=" operator. */ void ShareData(const Blob& other); /** * @brief Set the diff_ shared_ptr to point to the SyncedMemory holding the * diff_ of Blob other -- useful in Layer%s which simply perform a copy * in their Forward pass. * * This deallocates the SyncedMemory holding this Blob's diff_, as * shared_ptr calls its destructor when reset with the "=" operator. */ void ShareDiff(const Blob& other); //判断形状是否相等 bool ShapeEquals(const BlobProto& other); protected: shared_ptr<SyncedMemory> data_;//前向传播的数据， shared_ptr<SyncedMemory> diff_;//反向传播的数据 shared_ptr<SyncedMemory> shape_data_;//旧的形状数据 vector<int> shape_;//新的形状数据 int count_;//数据的个数 int capacity_;//容量 DISABLE_COPY_AND_ASSIGN(Blob); }; // class Blob } // namespace caffe #endif // CAFFE_BLOB_HPP_
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