一个Python实现的精简版遗传算法
本文使用Python实现的精简版遗传算法，算法中仅采用变异算子而没有使用交叉算子，但是进化依然很有效，具体源代码如下：
from string import ascii_lowercase
from random import choice, random
target = list("welcome to http://www.cnhup.com")
charset = ascii_lowercase + ' .:/'
parent = [choice(charset) for _ in range(len(target))]
minmutaterate = .09
C = range(100)
perfectfitness = len(target)
def fitness(trial):
return sum(t==h for t,h in zip(trial, target))
def mutaterate(parent):
return 1.0-(1.0*(perfectfitness - fitness(parent)) / perfectfitness * (1.0 - minmutaterate))
def mutate(parent, rate):
return [(ch if random() <= rate else choice(charset)) for ch in parent]
def log(iterations,rate,parent):
print ("#%-4i, rate: %4.3f, fitness: %4.1f%%, '%s'" %
(iterations, rate, fitness(parent)*100./perfectfitness, ''.join(parent)))
iterations = 0
while parent != target:
rate = mutaterate(parent)
iterations += 1
if iterations % 10 == 0: log(iterations,rate,parent)
copies = [ mutate(parent, rate) for _ in C ] + [parent]
parent = max(copies, key=fitness)
print ()
log(iterations,rate,parent)
