#!/usr/bin/python

# -*- coding: UTF-8 -*-

import numpy as np

def max_pool_forward(x, pool_param):

(N, C, H, W) = x.shape # 获取输入矩阵的参大小

pool_height = pool_param['pool_height']

pool_width = pool_param['pool_width']

stride = pool_param['stride']

H_prime = 1 + (H - pool_height) / stride # 输出高

W_prime = 1 + (W - pool_width) / stride # 输出宽

out = np.zeros((N, C, H_prime, W_prime))

for n in xrange(N):

for h in xrange(H_prime):

for w in xrange(W_prime):

# (h1, w1) 为当前pooling窗口第一个点

# (h2, w2) 为当前pooling窗口最后一个点

h1 = h * stride

h2 = h * stride + pool_height

w1 = w * stride

w2 = w * stride + pool_width

window = x[n, :, h1:h2, w1:w2] # 当前pooling窗口

win_l = window.reshape((C, pool_height * pool_width))

out[n, :, h, w] = np.max(win_l, axis=1)

return out

x = np.random.randint(5, size=(1, 1, 4, 4))

pool_param = {'pool_height': 2, 'pool_width': 2, 'stride': 2}

out = max_pool_forward(x, pool_param)