我正在通过 C++ 中的 ACO 实现来解决旅行推销员问题。但是，我发现到目前为止我构建的程序出现了分段错误。（注意：出于调试目的，我将算法限制为仅对菌落进行一次迭代）。
首先，我从一个文件中提取了总共 52 个城市，然后我将蚂蚁分配给每个城市，从它开始，每个城市都有相同数量的蚂蚁。
为了存储每对城市之间的距离，我使用了一个称为 Map（方阵）的双精度向量向量。但是，在执行过程中，这些向量似乎被删除了。在这种情况下，它发生在计算 55 号蚂蚁的路径时。我添加了一段代码只是为了突出显示它崩溃的确切位置：
//DEBUGGING SECTION
cout << "Size Roulette: " << Roulette.size() << endl;
cout << "Size Remain: " << RemainingCities.size() << endl;
cout << "Size Map: " << Map.size() << " x " << Map[0].size() << endl;
int k = 0;
cout << "Test: Map access: " << endl;
for(int i = 0; i < Map.size(); ++i) // HERE IT CRASHES AT ANT NUMBER 55
cout << Map[0][i] << " ";
cout << endl;
cout << "Test: Operation: " << Map[Colony[ant_i][city_i-1]][RemainingCities[k]] << endl;
Roulette[k] = pow((MAX_DIST - Map[Colony[ant_i][city_i-1]][RemainingCities[k]]), heur_coef) + pow((pheromones[Colony[ant_i][city_i-1]][RemainingCities[k]]), pher_coef);
//END OF DEBUGGING SECTION
在那里，函数 Map[0].size() 通常返回 52（就像 Map.size()，因为它应该是一个方阵），但在崩溃的迭代中，它返回看起来像一个内存地址的东西，并且当我尝试访问任何元素时，就会发生分段错误。
我检查了内存访问是否始终正确，并且在第 55 只蚂蚁之前，除了 Map 之外，我可以毫无问题地访问任何其他变量。我为轮盘赌方法尝试了不同的种子，但它总是在同一个地方崩溃。
我还改变了蚁群的数量。如果每个城市只有一只蚂蚁，则程序可以毫无问题地执行，但对于任何更高的数量，程序总是在第 55 只蚂蚁时崩溃。
您可以从 github 下载完整的 cpp 文件和读取的 .tsp 文件：
https://github.com/yitosmash/ACO
无论如何，我将在这里保留完整的功能：
void ACO(const vector<City>& cities, const vector<vector<double>>& Map, int max_it, int num_ants, double decay, double heur_coef, double pher_coef, double pher_coef_elit)
{
srand(30);
//Initialise colony of ants (each ant is a vector of city indices)
vector<vector<int>> Colony(num_ants, vector<int>(cities.size(), 0));
//Initialise pheromone matrix
vector<vector<double>> pheromones(cities.size(), vector<double>(cities.size(), 0));
//Initialise costs vector(for etilist expansion)
vector<double> costs(cities.size(), 0);
//Auxiliar vector of indices
vector<int> cityIndices(cities.size());
for (int i = 0; i < cities.size(); ++i)
cityIndices[i] = i;
//Longest distance from Map, used for heuristic values.
vector<double> longests(cities.size(), 0);
for(int i = 0; i < cities.size(); ++i)
longests[i] = *(max_element(Map[i].begin(), Map[i].end()));
const double MAX_DIST = *(max_element(longests.begin(), longests.end()));
longests.clear();
int i=0;
while(i<max_it)
{
for(int ant_i = 0; ant_i < num_ants; ++ant_i)
{
cout << "Ant: " << ant_i << endl;
//City for ant_i to start at; each ant is assigned a determined starting city
int starting_city = (int) ((float)ant_i/num_ants*cities.size());
//cout << starting_city << endl;
Colony[ant_i][0] = starting_city;
//Get a vector with the cities left to visit
vector<int> RemainingCities = cityIndices;
//Remove starting city from remaining cities
RemainingCities.erase(RemainingCities.begin() + starting_city);
//Create path for ant_i
for(int city_i = 1; city_i < Colony[ant_i].size(); ++city_i)
{
cout << "Calculating city number: " << city_i << endl;
//Create roulette for next city selection
vector<double> Roulette(RemainingCities.size(), 0);
double total = 0;
//DEBUGGING SECTION
cout << "Size Roulette: " << Roulette.size() << endl;
cout << "Size Remain: " << RemainingCities.size() << endl;
cout << "Size Map: " << Map.size() << " x " << Map[0].size() << endl;
int k = 0;
cout << "Test: Map access: " << endl;
for(int i = 0; i < Map.size(); ++i) // HERE IT CRASHES AT ANT NUMBER 55
cout << Map[0][i] << " ";
cout << endl;
cout << "Test: Operation: " << Map[Colony[ant_i][city_i-1]][RemainingCities[k]] << endl;
Roulette[k] = pow((MAX_DIST - Map[Colony[ant_i][city_i-1]][RemainingCities[k]]), heur_coef) + pow((pheromones[Colony[ant_i][city_i-1]][RemainingCities[k]]), pher_coef);
//END OF DEBUGGING SECTION
for(int j = 0; j < RemainingCities.size(); ++j)
{
//Heuristic value is MAX_DIST - current edge.
Roulette[j] = pow((MAX_DIST - Map[Colony[ant_i][city_i-1]][RemainingCities[j]]), heur_coef) + pow((pheromones[Colony[ant_i][city_i-1]][RemainingCities[j]]), pher_coef);
total += Roulette[j];
}
cout << endl;
//Transform roulette into stacked probabilities
Roulette[0] = Roulette[0]/total;
for(int j = 1; j < Roulette.size(); ++j)
Roulette[j] = Roulette[j-1] + Roulette[j] / total;
//Select a city from Roulette
int chosen = 0;
double r = (double) rand()/RAND_MAX;
while(Roulette[chosen] < r)
chosen++;
//Add chosen city to
Colony[ant_i][city_i] = RemainingCities[chosen];
RemainingCities.erase(RemainingCities.begin() + chosen);
}
cout << endl;
//Save cost of ant_i, for elitist expansion
costs[ant_i] = pathCost(Colony[ant_i], Map);
}
i++;
}
}