在caffe中，网络的结构由prototxt文件中给出，由一些列的Layer（层）组成，常用的层如：数据加载层、卷积操作层、pooling层、非线性变换层、内积运算层、归一化层、损失计算层等；本篇主要介绍pooling层
1. Pooling层总述
下面首先给出pooling层的结构设置的一个小例子（定义在.prototxt文件中）
layer {
name: "pool1" //该层的名称
type: "Pooling" //该层的类型
bottom: "norm1" //该层的输入数据blob
top: "pool1" //该层的输出数据blob
// 该层的相关参数设置
pooling_param {
pool: MAX //pooling类型，默认值为MAX，也可以设置为AVE，STOCHASTIC
kernel_size: //pooling核大小，为必设参数
stride: //pooling核步长，默认值为1（即重叠），但通常设置为2；
}
}注：在caffe的原始proto文件中，关于卷积层的参数PoolingParameter定义如下：
message PoolingParameter {
enum PoolMethod {
MAX = ;
AVE = ;
STOCHASTIC = ;
}
optional PoolMethod pool = [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 = [default = ]; // The padding size (equal in Y, X)
optional uint32 pad_h = [default = ]; // The padding height
optional uint32 pad_w = [default = ]; // The padding width
optional uint32 kernel_size = ; // The kernel size (square)
optional uint32 kernel_h = ; // The kernel height
optional uint32 kernel_w = ; // The kernel width
optional uint32 stride = [default = ]; // The stride (equal in Y, X)
optional uint32 stride_h = ; // The stride height
optional uint32 stride_w = ; // The stride width
enum Engine {
DEFAULT = ;
CAFFE = ;
CUDNN = ;
}
optional Engine engine = [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 = [default = false];
}