// the local pheromone update is done after each step (each ant one city step)
private void LocalPheromoneUpdate(int antIndex, int currentCityAmount)
{
int prevCity = Ants[antIndex].GetCityOfTour(currentCityAmount - 1);
int currentCity = Ants[antIndex].GetCityOfTour(currentCityAmount);
Pheromones.SetPheromone(prevCity, currentCity, ((1.0f - rho) * Pheromones.GetPheromone(prevCity, currentCity)) + (rho * tau0));
Pheromones.SetPheromone(currentCity, prevCity, Pheromones.GetPheromone(prevCity, currentCity));
choiceInfo.SetChoice(prevCity, currentCity, Math.Pow(Pheromones.GetPheromone(prevCity, currentCity), alpha) *
Math.Pow((1.0 / Distances.GetDistance(prevCity, currentCity)), beta));
choiceInfo.SetChoice(currentCity, prevCity, choiceInfo.GetChoice(prevCity, currentCity));
}
// choice update
public void UpdateChoiceInfo(Pheromones pheromones, Distances distances, int alpha, int beta)
{
for (int i = 0; i < size; i++)
{
for (int j = i + 1; j < size; j++)
{
choiceInfo[i][j] = Math.Pow(pheromones.GetPheromone(i, j), alpha) *
Math.Pow((1.0 / distances.GetDistance(i, j)), beta);
choiceInfo[j][i] = choiceInfo[i][j];
/* // To avoid small or high values
* if (choiceInfo[i][j] <= 0.000001)
* choiceInfo[i][j] = 0.000001;
* else if (choiceInfo[i][j] > (double.MaxValue / 100))
* choiceInfo[i][j] = double.MaxValue / 100;
*/
}
}
}