#?Back-Propagation?Neural?Networks
#
#?Written?in?Python.??See?http://www.python.org/
#
#?Neil?Schemenauer?

import?math
import?random
import?operator
import?string
import?sys

random.seed（0）

#?calculate?a?random?number?where:??a?<=?rand?def?rand（a?b）:
????return?（b-a）*random.random（）?+?a

#?Make?a?matrix?（we?could?use?NumPy?to?speed?this?up）
def?makeMatrix（I?J?fill=0.0）:
????m?=?[]
????for?i?in?range（I）:
????????m.append（[fill]*J）
????return?m

class?NN:
????def?__init__（self?ni?nh?no）:
????????#?number?of?input?hidden?and?output?nodes
????????self.ni?=?ni?+?1?#?+1?for?bias?node
????????self.nh?=?nh
????????self.no?=?no

????????#?activations?for?nodes
????????self.ai?=?[1.0]*self.ni
????????self.ah?=?[1.0]*self.nh
????????self.ao?=?[1.0]*self.no

????????#?create?weights
????????self.wi?=?makeMatrix（self.ni?self.nh）
????????self.wo?=?makeMatrix（self.nh?self.no）
????????#?set?them?to?random?vaules
????????for?i?in?range（self.ni）:
????????????for?j?in?range（self.nh）:
????????????????self.wi[i][j]?=?rand（-2.0?2.0）
????????for?j?in?range（self.nh）:
????????????for?k?in?range（self.no）:
????????????????self.wo[j][k]?=?rand（-2.0?2.0）

????????#?last?change?in?weights?for?momentum
????????self.ci?=?makeMatrix（self.ni?self.nh）
????????self.co?=?makeMatrix（self.nh?self.no）

????def?update（self?inputs）:
????????if?len（inputs）?!=?self.ni-1:
????????????raise?ValueError?‘wrong?number?of?inputs‘

????????#?input?activations
????????for?i?in?range（self.ni-1）:
????????????#self.ai[i]?=?1.0/（1.0+math.exp（-inputs[i]））
????????????self.ai[i]?=?inputs[i]

????????#?hidden?activations
????????for?j?in?range（self.nh）:
????????????sum?=?0.0
????????????for?i?in?range（self.ni）:
????????????????sum?=?sum?+?self.ai[i]?*?self.wi[i][j]
????????????self.ah[j]?=?1.0/（1.0+math.exp（-sum））

????????#?output?activations
????????for?k?in?range（self.no）:
????????????sum?=?0.0
????????????for?j?in?range（self.nh）:
????????????????sum?=?sum?+?self.ah[j]?*?self.wo[j][k]
????????????self.ao[k]?=?1.0/（1.0+math.exp（-sum））

????????return?self.ao[:]


????def?backPropagate（self?targets?N?M）:
????????if?len（targets）?!=?self.no:
????????????raise?ValueError?‘wrong?number?of?target?values‘

????????#?calculate?error?terms?for?output
????????output_deltas?=?[0.0]?*?self.no
????????for?k?in?range（self.no）:
????????????ao?=?self.ao[k]
????????????output_deltas[k]?=?ao*（1-ao）*（targets[k]-ao）

????????#?calculate?error?terms?for?hidden
????????hidden_deltas?=?[0.0]?*?self.nh
????????for?j?in?range（self.nh）:
????????????sum?=?0.0
????????????for?k?in?range（self.no）:
????????????????sum?=?sum?+?output_deltas[k]*self.wo[j][k]
????????????hidden_deltas[j]?=?self.ah[j]*（1-self.ah[j]）*sum

????????#?update?output?weights
????????for?j?in?range（self.nh）:
????????????for?k?in?range（self.no）:
????????????????change?=?output_deltas[k]*self.ah[j]
???????????

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----

?????文件???????4797??2001-05-21?16:30??neural_net_1\bpnn.py

?????文件???????2402??2001-05-21?13:07??neural_net_1\code2data.py

?????文件??????41500??2001-06-07?02:13??neural_net_1\code_recog.test

?????文件???????3593??2001-05-21?13:31??neural_net_1\code_recognizer.py

?????文件?????142780??2001-06-07?02:12??neural_net_1\testdata.1k

?????文件?????744810??2001-06-07?02:13??neural_net_1\testdata.200

?????文件?????293480??2001-06-07?02:13??neural_net_1\testdata.500

?????目錄??????????0??2014-10-10?16:19??neural_net_1

-----------?---------??----------?-----??----

??????????????1233362????????????????????8