caffe中的Blob块

首先说明：Blob定义了一个类模板。

让我们看一下Blob的头文件里有什么哈：

定义了一个全局变量：

const int kMaxBlobAxes = 32;

看看它的构造函数：

Blob() : data_(), diff_(), count_(0), capacity_(0) {}；

explicit Blob(const int num, const int channels, const int height，const int width);

explicit Blob(const vector<int>& shape);

Reshape函数：

void Reshape(const int num, const int channels, const int height, const int width);
void Reshape(const vector<int>& shape);
void Reshape(const BlobShape& shape);

void ReshapeLike(const Blob& other);

内联函数shape_string:作用就是把shape的数据变为字符输出，里面用到了ostringstream流；

inline string shape_string() const {
    ostringstream stream;
    for (int i = 0; i < shape_.size(); ++i) {
      stream << shape_[i] << " ";
    }
    stream << "(" << count_ << ")";
    return stream.str();
  }

内联函数shape():

//作用：返回shape_的引用；
inline const vector<int>& shape() const { return shape_; }
//作用：输入第几维度，返回该维度的大小；
inline int shape(int index) const {
    return shape_[CanonicalAxisIndex(index)];

//内联函数：num_axes(),作用：返回是多少维度的块；
inline int num_axes() const { return shape_.size(); }

//内联函数：count():
inline int count() const { return count_; }   //返回一共多少数据啊，；
inline int count(int start_axis, int end_axis) const //返回输入的索引之间的大小；
inline int count(int start_axis) const  //太麻烦了，不写了，自己看代码吧；

canonicalAxisIndex的作用就是：把正的索引不变，负的改为正的，另外，还是检查一下它们的范围啦；

CanonicalAxisIndex(int axis_index) const

offset函数就是计算一下索引的偏移值，因为吧，多维数组在内存里也是按一维 存放的：

inline int offset(const int n, const int c = 0, const int h = 0, const int w = 0) const {

……

return ((n * channels() + c) * height() + h) * width() + w;

}

// 用向量的方式把坐标值传入：
inline int offset(const vector<int>& indices) const

函数copyfrom，作用把数据从Blob块中复制到内存中

void CopyFrom(const Blob<Dtype>& source, bool copy_diff = false, bool reshape = false);

查看数据的函数：

inline Dtype data_at(const int n, const int c, const int h, const int w) const
inline Dtype diff_at(const int n, const int c, const int h, const int w) const
 inline Dtype data_at(const vector<int>& index) const
inline Dtype diff_at(const vector<int>& index) const

获得data_与diff_的函数：

inline const shared_ptr<SyncedMemory>& data() const {
    CHECK(data_);
    return data_;
  }

inline const shared_ptr<SyncedMemory>& diff() const {
    CHECK(diff_);
    return diff_;
  }

另外还有好几个函数，尼玛，有点多哎

const Dtype* cpu_data() const;
  void set_cpu_data(Dtype* data);
  const int* gpu_shape() const;
  const Dtype* gpu_data() const;
  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();
  void Update();
  void FromProto(const BlobProto& proto, bool reshape = true);
  void ToProto(BlobProto* proto, bool write_diff = false) const;

  /// @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;
  /// @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);

还有：

/**
   * @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.
   *
   * 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);

  bool ShapeEquals(const BlobProto& other);

下面是定义的变量：

shared_ptr<SyncedMemory> data_;
  shared_ptr<SyncedMemory> diff_;
  shared_ptr<SyncedMemory> shape_data_;
  vector<int> shape_;
  int count_;
  int capacity_;