标签：慕课 导论 CODE bp w2 w1 w0 x0 x1

目标值 与 误差值，反了。 没发现原因 ~

import math
def back_propagation(x0,x1,w0,w1,w2,y,N):
#     y = 1 / (1 + math.exp( -((x0 * w0)  + (x1 * w1) + w2)))   
    print("\n=============================NO",N,"=============================")
    N = N-1
    f1 = x0 * w0
    f2 = x1 * w1
    f3 = f1 + f2
    f4 = f3 + w2
    f5 = -f4
    f6= math.exp(f5)
    f7 = 1 + f6
    f8 = 1/f7
     # MSE 
#     error = 0.5 * math.pow((y - f8),2)   
    error = y - f8
    print("RESULT,               ERROR\n" ,f8, error)    
#     print("----------------END---Forward-------------------------")
    bp1 = -(1/math.pow(f7,2)) * error
    bp2 = 1 * bp1
    bp3 = math.exp(f5) * bp2
    bp4 = -bp3
    bp5 = bp4
    bp6 = bp5
    bp_w1 = bp6 * x1
#     bp_x1 = bp6 * w1
    bp_w0 = bp6 * x0
#     bp_x0 = bp6 * w0
    bp_w2 = bp5
    w0 = w0 - bp_w0
    w1 = w1 - bp_w1
    w2 = w2 - bp_w2
#     print(bp1,bp2,bp3)
#     print(bp4,bp5,bp6)
    print("----------------END---BP----Update w---------------------")
    print("x0:" , x0,"x1:" , x1,"y:" , y) 
#     print("bp_w0:" , bp_w0,"bp_w1:" , bp_w1,"bp_w2:" , bp_w2) 
    print("w0:" , w0,"w1:" , w1,"w2:" , w2)
    if (N > 0):
        back_propagation(x0,x1,w0,w1,w2,y,N)
    return 

x0 = -1
x1 = -2
w0 = 2
w1 = -3
w2 = -3
y = 1.73
N = 10
back_propagation(x0,x1,w0,w1,w2,y,N)

=============================NO 10 =============================
RESULT,               ERROR
 0.7310585786300049 0.9989414213699951
----------------END---BP----Update w---------------------
x0: -1 x1: -2 y: 1.73
w0: 2.1964038040505485 w1: -2.607192391898903 w2: -3.1964038040505485

=============================NO 9 =============================
RESULT,               ERROR
 0.45551225254229843 1.2744877474577017
----------------END---BP----Update w---------------------
x0: -1 x1: -2 y: 1.73
w0: 2.5125033261603766 w1: -1.9749933476792467 w2: -3.5125033261603766

=============================NO 8 =============================
RESULT,               ERROR
 0.11154856232322807 1.618451437676772
----------------END---BP----Update w---------------------
x0: -1 x1: -2 y: 1.73
w0: 2.6729007336654407 w1: -1.6541985326691184 w2: -3.6729007336654407

=============================NO 7 =============================
RESULT,               ERROR
 0.045764387022953316 1.6842356129770466
----------------END---BP----Update w---------------------
x0: -1 x1: -2 y: 1.73
w0: 2.7464513161952797 w1: -1.50709736760944 w2: -3.7464513161952797

=============================NO 6 =============================
RESULT,               ERROR
 0.02992416510794365 1.7000758348920564
----------------END---BP----Update w---------------------
x0: -1 x1: -2 y: 1.73
w0: 2.7958023236502387 w1: -1.4083953526995214 w2: -3.7958023236502387

=============================NO 5 =============================
RESULT,               ERROR
 0.022426856120331854 1.7075731438796682
----------------END---BP----Update w---------------------
x0: -1 x1: -2 y: 1.73
w0: 2.833238973256924 w1: -1.3335220534861503 w2: -3.833238973256924

=============================NO 4 =============================
RESULT,               ERROR
 0.0179962126173677 1.7120037873826324
----------------END---BP----Update w---------------------
x0: -1 x1: -2 y: 1.73
w0: 2.863494101589214 w1: -1.2730117968215704 w2: -3.863494101589214

=============================NO 3 =============================
RESULT,               ERROR
 0.015053680787498781 1.7149463192125012
----------------END---BP----Update w---------------------
x0: -1 x1: -2 y: 1.73
w0: 2.8889217263926086 w1: -1.222156547214781 w2: -3.8889217263926086

=============================NO 2 =============================
RESULT,               ERROR
 0.012951208624576063 1.717048791375424
----------------END---BP----Update w---------------------
x0: -1 x1: -2 y: 1.73
w0: 2.9108715763814192 w1: -1.1782568472371597 w2: -3.9108715763814192

=============================NO 1 =============================
RESULT,               ERROR
 0.01137126330526271 1.7186287366947373
----------------END---BP----Update w---------------------
x0: -1 x1: -2 y: 1.73
w0: 2.9301923279002793 w1: -1.1396153441994392 w2: -3.9301923279002793

标签：慕课,导论,CODE,bp,w2,w1,w0,x0,x1
来源： https://www.cnblogs.com/hbuwyg/p/15547167.html

本站声明： 1. iCode9 技术分享网（下文简称本站）提供的所有内容，仅供技术学习、探讨和分享；
2. 关于本站的所有留言、评论、转载及引用，纯属内容发起人的个人观点，与本站观点和立场无关；
3. 关于本站的所有言论和文字，纯属内容发起人的个人观点，与本站观点和立场无关；
4. 本站文章均是网友提供，不完全保证技术分享内容的完整性、准确性、时效性、风险性和版权归属；如您发现该文章侵犯了您的权益，可联系我们第一时间进行删除；
5. 本站为非盈利性的个人网站，所有内容不会用来进行牟利，也不会利用任何形式的广告来间接获益，纯粹是为了广大技术爱好者提供技术内容和技术思想的分享性交流网站。