import math, random, time, numpy as np def distance(city1, city2): return math.sqrt((city1[0] - city2[0]) ** 2 + (city1[1] - city2[1]) ** 2) + 1e-10 def total_distance(cities): return sum([distance(cities[i - 1], cities[i]) for i in range(len(cities))]) class AntColony: def __init__(self, cities, n_ants, alpha=1, beta=2, evaporation=0.5, intensification=2, max_time=0.1): self.cities = cities self.n = len(cities) self.n_ants = n_ants self.alpha = alpha self.beta = beta self.evaporation = evaporation self.intensification = intensification self.max_time = max_time self.pheromones = [[1 / self.n for _ in range(self.n)] for __ in range(self.n)] def choose_next_city(self, ant): unvisited_cities = [i for i in range(self.n) if i not in ant] probabilities = [self.pheromones[ant[-1]][i] ** self.alpha * ((1 / self.distance(self.cities[ant[-1]], self.cities[i])) ** self.beta) for i in unvisited_cities] total = sum(probabilities) if total == 0: probabilities = [1 / len(unvisited_cities) for _ in unvisited_cities] else: probabilities = [p / total for p in probabilities] return np.random.choice(unvisited_cities, p=probabilities) def update_pheromones(self, ant): pheromones_delta = self.intensification / self.total_distance([self.cities[i] for i in ant]) for i in range(len(ant) - 1): self.pheromones[ant[i]][ant[i+1]] += pheromones_delta def run(self): best_ant = [] best_distance = float('inf') start_time = time.time() while time.time() - start_time < self.max_time: ants = [[random.randint(0, self.n - 1)] for _ in range(self.n_ants)] for ant in ants: for _ in range(self.n - 1): ant.append(self.choose_next_city(ant)) ant_distance = self.total_distance([self.cities[i] for i in ant]) if ant_distance < best_distance: best_distance = ant_distance best_ant = ant.copy() self.update_pheromones(ant) self.pheromones = [[(1 - self.evaporation) * p for p in row] for row in self.pheromones] return [self.cities[i] for i in best_ant]