std::multimap<double,unsigned int,Ant::MultiMapComp> Ant::get_feasible_vertices(OptimizationProblem &op, PheromoneMatrix &pheromones, double alpha, double beta) {
std::map<unsigned int,double> vertices;
bool should_debug = false;
if(current_vertex() == -1) {
vertices = op.get_feasible_start_vertices();
} else {
vertices = op.get_feasible_neighbours(current_vertex());
}
double denominator = 0.0;
std::map<unsigned int,double>::iterator it;
for(it=vertices.begin();it!=vertices.end();it++) {
unsigned int vertex = (*it).first;
double heuristic_value = (*it).second;
if(current_vertex() == -1) {
double numerator = pow(pheromones.get(pheromones.size()-1, vertex), alpha) * pow(heuristic_value, beta);
(*it).second = numerator;
denominator += numerator;
} else {
double numerator = pow(pheromones.get(current_vertex(), vertex), alpha) * pow(heuristic_value, beta);
(*it).second = numerator;
denominator += numerator;
if (should_debug) {
std::cerr << "\tEdge to " << vertex << std::endl;
std::cerr << "\tpow(" << pheromones.get(current_vertex(), vertex) << "," << alpha << ") * pow(" << heuristic_value << "," << beta << ")" << std::endl;
std::cerr << "\tNumertor is " << numerator << " and current denom = " << denominator << std::endl;
}
}
}
std::multimap<double,unsigned int,MultiMapComp> probabilities;
for(it=vertices.begin();it!=vertices.end();it++) {
//std::cout << pheromones.get(pheromones.size()-1, (*it).first) << std::endl;
unsigned int vertex = (*it).first;
//double heuristic_value = (*it).second;
double probability;
if(denominator == 0) {
probability = 1.0 / vertices.size();
} else {
probability = (*it).second / denominator;
}
if (should_debug)
std::cerr << "Edge to " << vertex << " has probability " << probability << std::endl;
//std::cout << pheromones.get(current_vertex(), vertex) << " " << heuristic_value << std::endl;
//std::cout << "vertex: " << vertex << " heuristic: " << heuristic_value << " probability: " << probability << std::endl;
probabilities.insert(std::pair<double,unsigned int>(probability, vertex));
}
//std::cout << "***************************************" << std::endl;
return probabilities;
}
