神经网络python实现

前向传播

Example Feed-forward computation of a Neural Network

# -*- coding: utf-8 -*-
"""
Created on Wed Dec 21 21:18:19 2016

@author: CrazyVertigo
"""

import numpy as np

W1 = np.array([[1,1,1],[1,1,1],[1,1,1],[1,1,1]])
W2 = np.array([[1,1,1,1],[1,1,1,1],[1,1,1,1],[1,1,1,1]])
W3 = np.array([1,1,1,1])

b1 =1
b2 =1
b3 =1

f = lambda x: 1.0/(1.0 +np.exp(-x))
x = np.random.randn(3,1)
#print "x=",x
h1 = f(np.dot(W1,x) + b1)
#print "h1=",h1
h2 = f(np.dot(W2,h1) +b2)
#print "h2=",h2
out = np.dot(W3,h2) + b3
#print "out=",out