/*
* Adds the next edge in the path.
* This is probabilitically determined based on edge weight.
* The better the edge weight, the more likely it will be chosen.
*/
private void TakeNextEdge(Ant ant)
{
int currentCity = ant.Path[ant.Count - 1];
//Compile list of cities that the ant has NOT visited.
List <int> citiesNotVisited = new List <int>();
for (int i = 0; i < Cities.Length; i++)
{
if (!ant.AlreadyVisited(i) && distances[currentCity, i] != double.PositiveInfinity)
{
citiesNotVisited.Add(i);
}
}
if (citiesNotVisited.Count > 0)
{
double rowWeight = RowWeight(currentCity, citiesNotVisited);
int maxIndex = 0;
double max = 0;
List <double> probabilities = new List <double>();
for (int i = 0; i < citiesNotVisited.Count; i++)
{
probabilities.Add(EdgeWeight(currentCity, citiesNotVisited[i]) / rowWeight);
if (probabilities[i] > max)
{
max = probabilities[i];
maxIndex = i;
}
}
double bestEdgeRandom = random.NextDouble();
if (bestEdgeRandom < SELECT_BEST_PROBABILITY)
{
ant.Add(citiesNotVisited[maxIndex]);
}
else
{
double rand = random.NextDouble();
for (int i = 0; i < probabilities.Count; i++)
{
if (rand <= probabilities[i])
{
ant.Add(citiesNotVisited[i]);
return;
}
rand -= probabilities[i];
}
}
}
else
{
ResetAnt(ant);
}
}
/*
* Clears out the ant's path.
* The ant's new path is then started at a random city.
*/
private void ResetAnt(Ant ant)
{
ant.Path.Clear();
ant.Visited.Clear();
ant.Add(random.Next(0, Cities.Length));
}
