基于粒子群算法的运输费用优化方法代码
时间: 2023-05-24 11:03:04 浏览: 37
A:以下是使用粒子群算法进行运输费用优化的Python代码示例:
```python
import random
class Particle:
def __init__(self, x0):
self.position = []
self.velocity = []
self.best_position = []
self.fitness = -1
for i in range(num_dimensions):
self.velocity.append(random.uniform(-1, 1))
self.position.append(x0[i])
def evaluate_fitness(self, cost_func):
self.fitness = cost_func(self.position)
if self.fitness < self.best_fitness:
self.best_fitness = self.fitness
self.best_position = self.position
def update_velocity(self, best_position):
for i in range(num_dimensions):
r1 = random.random()
r2 = random.random()
social = c1 * r1 * (best_position[i] - self.position[i])
cognitive = c2 * r2 * (self.best_position[i] - self.position[i])
self.velocity[i] = w * self.velocity[i] + social + cognitive
def update_position(self, bounds):
for i in range(num_dimensions):
self.position[i] = self.position[i] + self.velocity[i]
if self.position[i] > bounds[i][1]:
self.position[i] = bounds[i][1]
if self.position[i] < bounds[i][0]:
self.position[i] = bounds[i][0]
def get_position(self):
return self.position
def PSO(cost_func, x0, bounds, num_particles, maxiter):
global num_dimensions
num_dimensions = len(x0)
best_global_position = []
best_global_fitness = -1
swarm = []
for i in range(num_particles):
swarm.append(Particle(x0))
for i in range(maxiter):
for j in range(num_particles):
swarm[j].evaluate_fitness(cost_func)
if swarm[j].fitness > best_global_fitness:
best_global_fitness = swarm[j].fitness
best_global_position = list(swarm[j].position)
for j in range(num_particles):
swarm[j].update_velocity(best_global_position)
swarm[j].update_position(bounds)
return best_global_position
```
在以上代码中,num_dimensions 变量是粒子的维度,也就是运输方案的变量个数。在代码中,为每个粒子初始化了运输方案变量的位置和速度,通过 evaluate_fitness 函数来评估每个粒子的适应度(即费用),将费用最佳的方案作为粒子当前的最佳位置。update_velocity 函数用于更新粒子的速度,update_position 函数用于更新粒子的位置,get_position 函数用于获取每个粒子当前的位置。最后在 PSO 函数中,初始化一个粒子群,并在一定的迭代次数内循环更新每个粒子的位置和速度,评估每个粒子的费用,并行情况下更新全局最优解。函数返回全局最优解的位置。