private double[] MoveProbs(int cityX, bool[] visited, Pheromone pheromone, int[][] dists)
{
// for ant, located at nodeX, with visited[], return the prob of moving to each city
int numCities = pheromone.Size;
double[] taueta = new double[numCities];
// inclues cityX and visited cities
double sum = 0.0;
// sum of all tauetas
// i is the adjacent city
for (int i = 0; i <= taueta.Length - 1; i++)
{
if (i == cityX)
{
taueta[i] = 0.0;
// prob of moving to self is 0
}
else if (visited[i])
{
taueta[i] = 0.0;
// prob of moving to a visited city is 0
}
else
{
taueta[i] = Math.Pow(pheromone.Get(cityX, i), alpha) * Math.Pow((1.0 / Distance(cityX, i, dists)), beta);
// could be huge when pheromone[][] is big
if (taueta[i] < 0.0001)
{
taueta[i] = 0.0001;
}
else if (taueta[i] > (double.MaxValue / (numCities * 100)))
{
taueta[i] = double.MaxValue / (numCities * 100);
}
}
sum += taueta[i];
}
double[] probs = new double[numCities];
for (int i = 0; i <= probs.Length - 1; i++)
{
probs[i] = taueta[i] / sum;
// big trouble if sum = 0.0
}
return(probs);
}
private void UpdatePheromones(Pheromone pheromone, Ant[] ants, int[][] dists)
{
for (int i = 0; i <= pheromone.Size - 1; i++)
{
for (int j = i + 1; j <= pheromone.Size - 1; j++)
{
for (int k = 0; k <= ants.Length - 1; k++)
{
double length = Length(ants[k].Trail, dists);
// length of ant k trail
double decrease = (1.0 - rho) * pheromone.Get(i, j);
double increase = 0.0;
if (EdgeInTrail(i, j, ants[k].Trail))
{
increase = (Q / length);
}
pheromone.Set(i, j, decrease + increase);
}
}
}
}