用python编写一个名字为MOHIG的代码,它结合了遗传算子和迭代贪婪启发式,主要组成部分包括编码和解码、初始化、选择、交叉、突变、破坏和重建、局部搜索和精英主义策略
时间: 2024-04-30 14:24:53 浏览: 115
基于python的遗传算法设计与实现
以下是一个基于遗传算法和迭代贪婪启发式的代码,名为MOHIG:
```python
import random
# 编码和解码
def encode(solution):
return [int(x) for x in list(solution)]
def decode(encoded_solution):
return ''.join([str(x) for x in encoded_solution])
# 初始化
def initialize_population(population_size, solution_length):
population = []
for i in range(population_size):
solution = ''.join(random.choice(['0', '1']) for _ in range(solution_length))
population.append(encode(solution))
return population
# 选择
def selection(population, fitness_scores):
total_fitness = sum(fitness_scores)
probabilities = [fitness_score / total_fitness for fitness_score in fitness_scores]
population_with_probabilities = list(zip(population, probabilities))
selected_population = []
for i in range(len(population)):
selected_solution = random.choices(population_with_probabilities, k=1, weights=probabilities)[0][0]
selected_population.append(selected_solution)
return selected_population
# 交叉
def crossover(parent1, parent2):
crossover_point = random.randint(1, len(parent1)-1)
child1 = parent1[:crossover_point] + parent2[crossover_point:]
child2 = parent2[:crossover_point] + parent1[crossover_point:]
return child1, child2
# 突变
def mutation(solution, mutation_rate):
mutated_solution = []
for gene in solution:
if random.random() < mutation_rate:
mutated_solution.append(int(not gene))
else:
mutated_solution.append(gene)
return mutated_solution
# 破坏和重建
def destroy_and_rebuild(population, elite_size, solution_length):
new_population = []
elites = sorted(population, key=lambda x: fitness_function(x), reverse=True)[:elite_size]
for i in range(len(population)-elite_size):
mutated_solution = mutation(random.choice(elites), 0.1)
new_population.append(mutated_solution)
new_population += elites
while len(new_population) < len(population):
new_population.append(encode(''.join(random.choice(['0', '1']) for _ in range(solution_length))))
return new_population
# 局部搜索
def local_search(solution):
best_solution = solution
for i in range(len(solution)):
mutated_solution = solution[:]
mutated_solution[i] = int(not solution[i])
if fitness_function(mutated_solution) > fitness_function(best_solution):
best_solution = mutated_solution
return best_solution
# 精英主义策略
def elitism(population, elite_size):
elites = sorted(population, key=lambda x: fitness_function(x), reverse=True)[:elite_size]
return elites
# 主函数
def MOHIG(population_size, solution_length, max_generations):
population = initialize_population(population_size, solution_length)
for i in range(max_generations):
fitness_scores = [fitness_function(solution) for solution in population]
elites = elitism(population, 2)
selected_population = selection(population, fitness_scores)
new_population = []
for j in range(population_size // 2):
parent1, parent2 = random.choices(selected_population, k=2)
child1, child2 = crossover(parent1, parent2)
child1 = mutation(child1, 0.1)
child2 = mutation(child2, 0.1)
child1 = local_search(child1)
child2 = local_search(child2)
new_population.append(child1)
new_population.append(child2)
new_population = destroy_and_rebuild(new_population, 2, solution_length)
new_population += elites
population = new_population
return decode(sorted(population, key=lambda x: fitness_function(x), reverse=True)[0])
```
这个代码实现了以下组成部分:
- 编码和解码:将基因型编码为二进制序列,或将二进制序列解码为基因型。
- 初始化:随机生成一定数量的初始种群。
- 选择:根据适应度函数的值,从种群中选择一部分个体作为下一代的父代。
- 交叉:随机选择两个父代,进行杂交操作,生成两个子代。
- 突变:对子代进行一定概率的基因突变。
- 破坏和重建:随机选择精英个体中的一个,进行基因突变操作,生成新的个体,用这些新的个体替换一部分原有的个体。
- 局部搜索:对子代进行一定次数的局部搜索,以提高其适应度函数的值。
- 精英主义策略:选择适应度函数值最高的一部分个体作为下一代的精英个体,防止种群过早陷入局部最优解。
其中,fitness_function() 是一个自定义的适应度函数,用于评估每个个体的适应度。
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