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# Genetic algorithm to solve the location problem of emergency logistics center

darren895 注册会员
2023-02-26 19:26
code example, can be used to solve the emergency logistics center location problem.

``````% 问题描述：
% 在地图上选址建立应急物流中心，使得从任意一个点到最近的应急物流中心的距离最小。
% 用遗传算法求解。

% 初始化参数
num_centers = 10;       % 应急物流中心数量
num_genes = 2;          % 基因数量，即坐标 (x,y)
population_size = 50;   % 种群大小
generation_limit = 200; % 迭代次数上限

% 初始化地图
map_size = [100 100];   % 地图大小
num_points = 500;       % 随机生成点的数量
points = rand(num_points, 2) .* repmat(map_size, num_points, 1);

% 初始化种群
population = rand(population_size, num_centers*num_genes) .* repmat(map_size, population_size, num_centers);
fitness = zeros(population_size, 1);

% 迭代优化
for generation = 1:generation_limit
% 计算适应度
for i = 1:population_size
centers = reshape(population(i,:), num_genes, num_centers)';
distances = pdist2(points, centers);
fitness(i) = sum(min(distances, [], 2));
end

% 选择
[~, I] = sort(fitness, 'ascend');
elite = population(I(1),:);
new_population = zeros(population_size, num_centers*num_genes);
for i = 1:population_size-1
p1 = randi([1 10]);
p2 = randi([1 10]);
while p2 == p1
p2 = randi([1 10]);
end
parent1 = population(I(p1),:);
parent2 = population(I(p2),:);
child = zeros(1, num_centers*num_genes);
for j = 1:num_centers
crossover_point = randi([1 num_genes]);
child((j-1)*num_genes+1:j*num_genes) = [parent1((j-1)*num_genes+1:crossover_point), parent2(j*num_genes-crossover_point+1:j*num_genes)];
end
new_population(i,:) = child;
end

% 突变
mutation_rate = 0.01;
for i = 1:population_size-1
if rand() < mutation_rate
p1 = randi([1 10]);
gene_to_mutate = randi([1 num_genes]);
new_population(i, (p1-1)*num_genes+gene_to_mutate) = rand() * map_size(gene_to_mutate);
end
end

% 保留精英
new_population(population_size,:) = elite;

% 更新种群
population = new_population;
end

% 结果可视化
centers = reshape(elite, num_genes, num_centers)';
distances = pdist2(points, centers);
[min_distance, I] = min(distances, [], 2);
figure;
scatter(points(:,1), points(:,
``````

If it can solve your problem, I hope it can be adopted.

dragon4cn 注册会员
2023-02-26 19:26

the reference answer GPT ᴼ ᴾ ᴱ ᴺ ᴬ ᴵ < br / > is a kind of optimization algorithm, genetic algorithm(ga) can be used to solve the complicated optimization problems, including emergency logistics center location selection problem. The following are the basic steps of using genetic algorithm to solve the location problem of emergency logistics center:

• Define fitness functions: Fitness functions are functions that evaluate the merits of each possible solution. In the location problem of emergency logistics center, the fitness function can be determined according to the distribution, traffic route and distribution range of emergency materials. The better the fitness function is, the more suitable the scheme is for the final solution.

• Designing genetic coding: Genetic coding refers to transforming a problem into a genome for easy calculation by genetic algorithms. In the emergency logistics center location problem, the genetic code can be expressed as a sequence containing multiple locations, each location represents a potential emergency logistics center location.

• Initializes the population: The population is the set of all possible solutions. Initializing a population requires the random generation of multiple potential solutions. In the problem of location selection of emergency logistics center, multiple potential location sequences of emergency logistics center can be randomly generated.

• Selection and crossover: By selection and crossover, excellent solutions and genomes are merged to generate new solutions. The process of selection and crossover can be completed by the selection and crossover operator in genetic algorithm.

• Variation: During the iterative process of the genetic algorithm, some random variation is required for the solution to increase the diversity of the population. In the emergency logistics center location problem, the variation can be random exchange of two positions in the emergency logistics center location sequence.

• Repeated iteration: The above steps constitute a complete iterative process of genetic algorithm. In the iteration process, each iteration will generate a new population, and constantly optimize the fitness function, and finally get an optimal solution.

• Output result: After the completion of the genetic algorithm iteration, output the solution with the best fitness as the final result.

The above are the basic steps of using genetic algorithm to solve the location problem of emergency logistics center. It is necessary to design and implement the algorithm according to the actual situation.

``````import random

# 定义适应度函数
def fitness(solution):
# 计算方案的适应度，这里简单地假设适应度等于方案的总长度
return sum(solution)

# 定义基因编码和解码函数
def encode(solution):
# 将方案转化为基因序列
return solution

def decode(genes):
# 将基因序列转化为方案
return genes

# 初始化种群
def initialize_population(size, num_genes):
population = []
for i in range(size):
solution = [random.randint(0, 100) for j in range(num_genes)]
population.append(encode(solution))
return population

# 选择算子
def selection(population, fitness):
# 根据适应度函数选择优秀的解决方案
population_fitness = [fitness(genes) for genes in population]
total_fitness = sum(population_fitness)
probability = [fitness / total_fitness for fitness in population_fitness]
selected = random.choices(population, weights=probability, k=len(population))
return selected

# 交叉算子
def crossover(parents):
# 对两个解决方案进行交叉
pivot = random.randint(1, len(parents[0]) - 1)
child = parents[0][:pivot] + parents[1][pivot:]
return child

# 变异算子
def mutation(genes, rate):
# 对解决方案进行变异
for i in range(len(genes)):
if random.random() < rate:
genes[i] = random.randint(0, 100)
return genes

# 定义遗传算法函数
def genetic_algorithm(population_size, num_genes, fitness_func, selection_func, crossover_func, mutation_func, mutation_rate, num_generations):
population = initialize_population(population_size, num_genes)
for i in range(num_generations):
parents = [selection_func(population, fitness_func) for j in range(population_size)]
offspring = [crossover_func(parents[j:j+2]) for j in range(0, population_size, 2)]
population = [mutation_func(genes, mutation_rate) for genes in offspring]
best_solution = decode(min(population, key=fitness_func))
return best_solution

# 测试遗传算法
best_solution = genetic_algorithm(100, 10, fitness, selection, crossover, mutation, 0.01, 100)
print(best_solution)

``````

The above code implements the main steps of genetic algorithm, including initialization population, selection, crossover, mutation and other operations, and evaluates the pros and cons of each solution through fitness function. In practical applications, it is necessary to design appropriate fitness functions, gene encoding and decoding methods, and operators such as selection, crossover and mutation according to specific problems to achieve the optimal solution.

daiyong126 注册会员
2023-02-26 19:26

Part of the answer quotes GPT, GPT_Pro better problem solving
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cica1987 注册会员

Publish Time
2023-02-26 19:26
Update Time
2023-02-26 19:26