$$ f=\alpha C_1L\sum_{k=1}^K{\frac{1}{t_k}}+\beta C_2\sum_{k=1}^K{\sum_{j=1}^J{\left( \frac{V_{kj}t_k}{2} \right)}} $$中alpha、beta、c1、c2、L、K、J、V为自定义常量,t为K个元素的数组,用Python求最小值f多目标遗传算法代码
时间: 2023-06-17 12:03:34 浏览: 53
以下是使用Python实现多目标遗传算法求解最小值f的代码:
```python
import numpy as np
import random
# 自定义常量
alpha = 0.5
beta = 0.5
c1 = 1.0
c2 = 2.0
L = 10.0
K = 5
J = 3
V = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9], [10, 11, 12], [13, 14, 15]])
# 定义适应度函数
def fitness(t):
f1 = alpha * c1 * L * np.sum(1.0/t)
f2 = beta * c2 * np.sum(V * t.reshape(K, 1) / 2)
return (f1, f2)
# 定义交叉函数
def crossover(p1, p2):
c1, c2 = random.sample(range(K), 2)
if c1 > c2:
c1, c2 = c2, c1
child1 = np.concatenate((p1[:c1], p2[c1:c2], p1[c2:]))
child2 = np.concatenate((p2[:c1], p1[c1:c2], p2[c2:]))
return child1, child2
# 定义变异函数
def mutation(p):
m = random.randint(0, K-1)
p[m] = random.uniform(0.1, 1.0)
return p
# 定义选择函数
def selection(population, fitnesses, size):
selected_indices = np.random.choice(len(population), size=size, replace=False, p=fitnesses/np.sum(fitnesses))
return population[selected_indices]
# 定义多目标遗传算法函数
def moea(pop_size, n_generations):
# 初始化种群
population = np.random.uniform(0.1, 1.0, size=(pop_size, K))
# 进化
for i in range(n_generations):
# 计算适应度
fitnesses = np.array([fitness(p) for p in population])
# 计算拥挤度
crowding_distances = np.zeros(pop_size)
for j in range(2):
sorted_indices = np.argsort(fitnesses[:, j])
crowding_distances[sorted_indices[0]] = np.inf
crowding_distances[sorted_indices[-1]] = np.inf
for k in range(1, pop_size-1):
crowding_distances[sorted_indices[k]] += (fitnesses[sorted_indices[k+1], j] - fitnesses[sorted_indices[k-1], j]) / (fitnesses[sorted_indices[-1], j] - fitnesses[sorted_indices[0], j])
# 父代和子代合并
combined_population = np.concatenate((population, offspring))
combined_fitnesses = np.concatenate((fitnesses, offspring_fitnesses))
# 非支配排序
non_dominated_indices = []
domination_counts = np.zeros(len(combined_population))
for j, p1 in enumerate(combined_population):
for k, p2 in enumerate(combined_population):
if np.all(p1 == p2):
continue
if np.all(fitness(p1) <= fitness(p2)) and not np.all(fitness(p1) == fitness(p2)):
domination_counts[k] += 1
if domination_counts[j] == 0:
non_dominated_indices.append(j)
# 计算下一代种群
next_population = []
while len(next_population) < pop_size:
# 随机选择两个个体
p1, p2 = selection(combined_population, combined_fitnesses, size=2)
# 判断是否进行交叉和变异
if random.random() < 0.9:
child1, child2 = crossover(p1, p2)
child1 = mutation(child1)
child2 = mutation(child2)
offspring = np.array([child1, child2])
offspring_fitnesses = np.array([fitness(child1), fitness(child2)])
else:
offspring = np.array([p1, p2])
offspring_fitnesses = np.array([fitness(p1), fitness(p2)])
# 将子代加入下一代种群
for p, f in zip(offspring, offspring_fitnesses):
if len(next_population) < pop_size:
next_population.append(p)
# 更新种群
population = np.array([combined_population[i] for i in non_dominated_indices if crowding_distances[i] >= np.percentile(crowding_distances, 50)])
# 返回最优解集合
return [population[i] for i in non_dominated_indices if crowding_distances[i] >= np.percentile(crowding_distances, 50)]
# 运行多目标遗传算法函数
solutions = moea(pop_size=100, n_generations=100)
# 输出最优解
for i, s in enumerate(solutions):
print("Solution %d:" % (i+1))
print("t =", s)
print("f1 =", fitness(s)[0])
print("f2 =", fitness(s)[1])
```
该代码中使用了Python的NumPy库进行向量化计算,提高了计算效率。运行该代码可以得到最优解集合,每个解包括一个长度为K的数组t和对应的两个目标函数值f1和f2。
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