//---------------------------------------------------------------------------------------
// FITNESS FUNCTION
// fitness function = for each car route
// (sum of all city distances + distance from depot to first city
// + distance from last city back to depot)
// + sum of all service times in each city
public int EvaluateCost(Solution soln)
{
// go through array of routes
for (int x = 0; x < soln.GetLength(); x++)
{
LinkedList<int> route = soln.GetRoute(x);
if (route.Count > 0)
{
// distance from depot to first city
int city = Convert.ToInt16(route.First.Value);
soln.AddCost(depot[city]); //distance from depot to first
city = Convert.ToInt16(route.Last.Value);
soln.AddCost(depot[city]); //distance from depot to last
// go through route's cities and add distances
for (int a = 1; a < route.Count; a++)
{
//start with city -1 and city and add distances
soln.AddCost(distance[route.ElementAt(a - 1), route.ElementAt(a)]);
//add service times for each city
soln.AddCost(service[route.ElementAt(a - 1)]);
}
}
}
return soln.GetCost();
}
public bool SolutionAcceptanceConstraint(Solution best, Solution candidate)
{
if (CheckConstraint(candidate) == false)
{
return false; // reject candidate solution
}
if (best.GetCost() - candidate.GetCost() > 0) // candidate cost is less
{
return true; // candidate is accepted
}
else
{
// accpetance probability = e^-cost/temp
int negcost = candidate.GetCost() - (2 * candidate.GetCost());
double exp = (double)negcost / (double)temperature;
double prob = Math.Exp(exp); // acceptance probability
double threshold = r.NextDouble(); // acceptance threshold - random
if (prob.CompareTo(threshold) > 0) // if accept prob > accept thresh
{
//Console.WriteLine("probability of acceptance: {0}\nthreshold of acceptance: {1}",
// prob, threshold);
return true; // candidate accepted
}
}
return false; // candidate not accepted
}
