求解tsp问题,python实现,采用遗传算法,其中变异算子使用反转突变
时间: 2023-11-18 16:58:04 浏览: 266
很高兴回答你的问题。关于TSP问题的遗传算法实现,变异算子采用反转突变的思想,你可以参考以下的Python代码实现:
```python
import random
# 遗传算法参数设置
POPULATION_SIZE = 100 # 种群数量
CROSSOVER_PROBABILITY = 0.9 # 交叉概率
MUTATION_PROBABILITY = 0.2 # 变异概率
GENERATION_NUM = 100 # 迭代次数
# 城市坐标(这里只列举了5个城市,你可以根据实际情况进行修改)
CITY_COORDINATES = [[1, 1], [2, 3], [5, 4], [7, 2], [4, 7]]
# 计算个体适应度函数(这里采用路径总长度作为适应度函数)
def fitness(individual):
total_distance = 0
for i in range(len(individual) - 1):
# 计算两个城市之间的距离
distance = ((CITY_COORDINATES[individual[i]][0] - CITY_COORDINATES[individual[i+1]][0])**2 +
(CITY_COORDINATES[individual[i]][1] - CITY_COORDINATES[individual[i+1]][1])**2)**0.5
total_distance += distance
return 1 / total_distance
# 初始化种群
def init_population():
population = []
for i in range(POPULATION_SIZE):
individual = list(range(len(CITY_COORDINATES)))
random.shuffle(individual)
population.append(individual)
return population
# 选择操作
def selection(population):
fitness_sum = sum([fitness(individual) for individual in population])
p = [fitness(individual) / fitness_sum for individual in population]
cumulative_p = [sum(p[:i+1]) for i in range(len(p))]
parents = []
for i in range(len(population)):
r = random.random()
for j in range(len(cumulative_p)):
if r < cumulative_p[j]:
parents.append(population[j])
break
return parents
# 交叉操作
def crossover(parents):
children = []
for i in range(len(parents)):
parent1, parent2 = random.sample(parents, 2)
child = [-1] * len(parent1)
start = random.randint(0, len(parent1)-1)
end = random.randint(start, len(parent1)-1)
for j in range(start, end+1):
child[j] = parent1[j]
for j in range(len(parent2)):
if parent2[j] not in child:
for k in range(len(child)):
if child[k] == -1:
child[k] = parent2[j]
break
children.append(child)
return children
# 变异操作
def mutation(children):
for i in range(len(children)):
r = random.random()
if r < MUTATION_PROBABILITY:
start = random.randint(0, len(children[i])-1)
end = random.randint(start, len(children[i])-1)
children[i][start:end+1] = reversed(children[i][start:end+1])
return children
# 主函数
def tsp_ga():
population = init_population()
for i in range(GENERATION_NUM):
parents = selection(population)
children = crossover(parents)
children = mutation(children)
population = parents + children
population = sorted(population, key=lambda x: fitness(x), reverse=True)
population = population[:POPULATION_SIZE]
# 返回最优个体
return population[0], 1 / fitness(population[0])
# 测试代码
best_individual, best_fitness = tsp_ga()
print('Best individual:', best_individual)
print('Best fitness:', best_fitness)
```
需要注意的是,在上述代码中,并没有对变异算子进行“反转突变”的具体实现,而是利用了Python中的列表切片和反转函数进行实现。具体来说,变异操作中随机选择一个子序列,然后将该子序列进行反转处理即可。
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