想要蚁群算法解决旅行商问题(带坐标的),结果是成图像的,不需要创新,能在我电脑运行就行
import numpy as np
from ant_colony import AntColony
import matplotlib.pyplot as plt
# 获取用户输入的城市坐标
num_cities = int(input("请输入城市数量: "))
cities = []
for i in range(num_cities):
x, y = map(float, input(f"请输入城市{i+1}的坐标(x y): ").split())
cities.append([x, y])
cities = np.array(cities)
# 初始化蚂蚁群和参数
colony = AntColony(cities, 3, 5, 100, 0.95, alpha=1, beta=2)
# 运行蚁群算法
colony.run()
# 获取最优路径
best_path = colony.best_path
# 绘制城市位置
plt.scatter(cities[:,0], cities[:,1], color='red')
plt.plot(cities[:,0], cities[:,1], 'ro')
# 绘制路径
plt.plot(cities[best_path, 0], cities[best_path, 1], '->')
plt.show()
蚁群算法是一种启发式算法,可以应用于解决旅行商问题。以下是使用蚁群算法解决带坐标的旅行商问题的基本步骤:
对于你的需求,可以使用Python中的matplotlib库将结果可视化。以下是一个简单的示例代码,可以将结果输出为图像:
import numpy as np
import matplotlib.pyplot as plt
# 设置蚂蚁数量、迭代次数、信息素挥发率等参数
ant_num = 50
iter_max = 500
rho = 0.5
Q = 100
alpha = 1.0
beta = 2.0
# 初始化城市坐标和信息素浓度
city_num = 10
city_pos = np.random.rand(city_num, 2) * 100
pheromone = np.ones((city_num, city_num)) * 0.1
# 蚂蚁行动和信息素更新
best_path = []
best_length = float('inf')
for iter in range(iter_max):
all_paths = []
all_lengths = []
for i in range(ant_num):
path = [np.random.randint(city_num)]
length = 0
for j in range(city_num - 1):
current_city = path[-1]
probs = pheromone[current_city] ** alpha * (1 / np.linalg.norm(city_pos[current_city] - city_pos, axis=1)) ** beta
probs[path] = 0
next_city = np.random.choice(range(city_num), p=probs / probs.sum())
path.append(next_city)
length += np.linalg.norm(city_pos[current_city] - city_pos[next_city])
all_paths.append(path)
all_lengths.append(length)
if length < best_length:
best_path = path
best_length = length
pheromone *= (1 - rho)
for path, length in zip(all_paths, all_lengths):
for i in range(city_num - 1):
a, b = path[i], path[i+1]
pheromone[a][b] += Q / length
pheromone[b][a] += Q / length
# 输出最优路径和路径长度,并绘制图像
print("最优路径:", best_path)
print("最优路径长度:", best_length)
plt.scatter(city_pos[:, 0], city_pos[:, 1])
plt.plot(city_pos[best_path, 0], city_pos[best_path, 1], 'r-')
plt.show()
引用 皆我工具箱 小程序回复内容作答:
以下是一个使用蚁群算法解决旅行商问题的Python代码示例:
import numpy as np
import matplotlib.pyplot as plt
# 城市坐标
coordinates = np.array([[37, 52], [49, 49], [52, 64], [20, 26], [40, 30], [21, 47], [17, 63], [31, 62], [52, 33], [51, 21], [42, 41], [31, 32], [5, 25], [12, 42], [36, 16], [52, 41], [27, 23], [17, 33], [13, 13], [57, 58], [62, 42], [42, 57], [16, 57], [8, 52], [7, 38], [27, 68], [30, 48], [43, 67], [58, 48], [58, 27], [37, 69], [38, 46], [46, 10], [61, 33], [62, 63], [63, 69], [32, 22], [45, 35], [59, 15], [5, 6], [10, 17], [21, 10], [5, 64], [30, 15], [39, 10], [32, 39], [25, 32], [25, 55], [48, 28], [56, 37], [30, 40]], dtype=int)
num_ants = 50 # 蚂蚁数量
num_iterations = 100 # 迭代次数
decay_factor = 0.6 # 挥发因子,用于控制信息素挥发的速率
class Ant:
def __init__(self, coordinates):
self.coordinates = coordinates
self.num_cities = coordinates.shape[0]
self.path = []
self.visited = np.zeros(self.num_cities)
self.curr_city = None
self.path_length = 0
def calculate_distance(city1, city2):
return np.linalg.norm(city1 - city2)
def update_pheromone(pheromone, ants):
for ant in ants:
for i in range(ant.num_cities - 1):
city1 = ant.path[i]
city2 = ant.path[i + 1]
pheromone[city1, city2] += 1 / ant.path_length
pheromone[city2, city1] += 1 / ant.path_length
def travel_salesman(coordinates, num_ants, num_iterations, decay_factor):
num_cities = coordinates.shape[0]
pheromone = np.ones((num_cities, num_cities)) # 初始化信息素矩阵
best_path_length = float('inf')
best_path = []
for iteration in range(num_iterations):
ants = [Ant(coordinates) for _ in range(num_ants)]
for ant in ants:
ant.curr_city = np.random.randint(num_cities)
ant.visited[ant.curr_city] = 1
ant.path.append(ant.curr_city)
for _ in range(num_cities - 1):
for ant in ants:
probabilities = []
for city in range(num_cities):
if ant.visited[city] == 0:
probabilities.append(pheromone[ant.curr_city, city])
else:
probabilities.append(0)
probabilities = np.array(probabilities) / sum(probabilities)
next_city = np.random.choice(range(num_cities), p=probabilities)
ant.path_length += calculate_distance(coordinates[ant.curr_city], coordinates[next_city])
ant.curr_city = next_city
ant.path.append(next_city)
ant.visited[next_city] = 1
for ant in ants:
ant.path_length += calculate_distance(coordinates[ant.path[-1]], coordinates[ant.path[0]])
if ant.path_length < best_path_length:
best_path_length = ant.path_length
best_path = ant.path
update_pheromone(pheromone, ants)
pheromone *= decay_factor
return best_path, best_path_length
best_path, best_path_length = travel_salesman(coordinates, num_ants, num_iterations, decay_factor)
print("Best Path:", best_path)
print("Best Path Length:", best_path_length)
# 绘制最佳路径
best_path_coordinates = coordinates[best_path]
x = best_path_coordinates[:, 0]
y = best_path_coordinates[:, 1]
x = np.append(x, x[0])
y = np.append(y, y[0])
plt.plot(x, y, 'ro-')
plt.show()
此代码使用蚁群算法解决旅行商问题,并将最佳路径绘制为图像。您只需将城市坐标和相关参数作为输入,并运行代码即可。
旅行商问题(Traveling Salesman Problem,TSP)是经典的组合优化问题,其目标是在给定一组城市和每对城市之间的距离,找到访问每个城市一次并返回到原点的最短路径。这个问题是NP难的,因此没有已知的高效算法来解决大规模问题。然而,蚁群算法是一种启发式算法,可以用来近似解决TSP问题。
以下是一个简单的Python程序,使用蚁群算法来解决TSP问题。这个程序使用了NetworkX库来生成随机图,然后使用蚁群算法来找到最短路径。我们将结果可视化成图像,用Matplotlib库来绘制城市和路径。
import networkx as nx
import matplotlib.pyplot as plt
from ant_algorithm import AntAlgorithm
# 生成随机图
num_cities = 10 # 城市数量
G = nx.random_geometric_graph(num_cities, 0.5)
# 计算城市之间的距离
distances = nx.all_pairs_dijkstra_path_length(G)
# 蚁群算法
algorithm = AntAlgorithm(distances, alpha=1, beta=5, rho=0.5, q=0.1, n_ants=100, max_iter=500)
algorithm.run()
# 最短路径和长度
best_path = algorithm.best_path
best_length = algorithm.best_length
# 绘制图像
pos = nx.spring_layout(G)
nx.draw(G, pos, node_size=500, node_color='lightblue', with_labels=True)
nx.draw_networkx_edges(G, pos, width=2, edge_color='gray')
nx.draw_networkx_nodes(G, pos, nodelist=[best_path[0]], node_size=700, node_color='red')
nx.draw_networkx_nodes(G, pos, nodelist=best_path[1:], node_size=700, node_color='green')
plt.axis('off')
plt.show()
注意,上述代码中的 AntAlgorithm
需要您自己实现,它应该包含以下方法:
__init__(self, distances, alpha, beta, rho, q, n_ants, max_iter)
:初始化蚁群算法的参数。run(self)
:运行蚁群算法,找到最短路径和对应的长度。best_path(self)
:返回当前找到的最短路径。best_length(self)
:返回当前找到的最短路径的长度。这是一个基本的实现,可能需要您根据自己电脑的性能和问题的规模进行适当的调整。
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牛顿迭代法可以推广到多元非线性方程组 F(x)=0的情况,称为牛顿-- 拉夫逊方法 (Newton-Raphson method). 当 F(x)F(x)F(x) 关于 xxx 的 Jacobi 矩阵J(x)=(∂F∂x)\boldsymbol{J}(\boldsymbol{x}) = (\cfrac{\partial \boldsymbol{F}}{\partial \boldsymbol{x}})J(x)=(∂x∂F) 可逆时, 有
x(k+1)=x(k)−J−1(x(k))F(x(k)),\boldsymbol{x}^{(k+1)}=\boldsymbol{x}^{(k)}- \boldsymbol{J}^{-1}(\boldsymbol{x}^{(k)})\boldsymbol{F}(\boldsymbol{x}^{(k)}),x(k+1)=x(k)−J−1(x(k))F(x(k)),,
求解步骤:
求解非线性方程组的Newton-Raphson方法:
1、 取初始点 x(0),最大迭代次数 N 和精度要求 ε, 置 k=0;
2、 求解线性方程组 J(xk)d=−F(xk)J(x^k)d=−F(x^k)J(xk)d=−F(xk);
3、 若 |d|<ε, 则停止计算;否则,置xk+1=xk+dkx^{k+1}=x^k+d^kxk+1=xk+dk;
4、 若 k=N, 则停止计算;否则,置 k=k+1, 转(2).