1. Pooling層總述

下面首先給出pooling層的結構設定的一個小例子（定義在.prototxt檔案中） 

layer {
  name: "pool1"   //該層的名稱
  type: "Pooling"  //該層的型別
  bottom: "norm1"  //該層的輸入資料blob
  top: "pool1"   //該層的輸出資料blob

  // 該層的相關引數設定
  pooling_param {
    pool: MAX  //pooling型別，預設值為MAX，也可以設定為AVE，STOCHASTIC
    kernel_size: 3  //pooling核大小，為必設引數
    stride: 2
 
  //pooling核步長，預設值為1（即重疊），但通常設定為2；
  }

}

注：在caffe的原始proto檔案中，關於卷積層的引數PoolingParameter定義如下：

message PoolingParameter {
  enum PoolMethod {
    MAX = 0;
    AVE = 1;
    STOCHASTIC = 2;
  }
  optional PoolMethod pool = 1 [default = MAX]; // The pooling method
  // Pad, kernel size, and stride are all given as a single value for equal
  
 
// dimensions in height and width or as Y, X pairs.
  optional uint32 pad = 4 [default = 0]; // The padding size (equal in Y, X)
  optional uint32 pad_h = 9 [default = 0]; // The padding height
  optional uint32 pad_w = 10 [default = 0]; // The padding width
  optional uint32 kernel_size = 2; // The kernel size (square)
 

  optional uint32 kernel_h = 5; // The kernel height
  optional uint32 kernel_w = 6; // The kernel width
  optional uint32 stride = 3 [default = 1]; // The stride (equal in Y, X)
  optional uint32 stride_h = 7; // The stride height
  optional uint32 stride_w = 8; // The stride width
  enum Engine {
    DEFAULT = 0;
    CAFFE = 1;
    CUDNN = 2;
  }
  optional Engine engine = 11 [default = DEFAULT];
  // 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];
}