private int SelectCityBiasedByNeighborDistance(IRandom random, Tour tour, IVRPEncoding solution)
{
int cityIndex = -1;
double sum = 0.0;
double[] probabilities = new double[tour.Stops.Count];
for (int i = 0; i < tour.Stops.Count; i++)
{
int next;
if (i + 1 >= tour.Stops.Count)
{
next = 0;
}
else
{
next = tour.Stops[i + 1];
}
double distance = ProblemInstance.GetDistance(
tour.Stops[i], next, solution);
int prev;
if (i - 1 < 0)
{
prev = 0;
}
else
{
prev = tour.Stops[i - 1];
}
distance += ProblemInstance.GetDistance(
tour.Stops[i], prev, solution);
probabilities[i] = distance;
sum += probabilities[i];
}
double rand = random.NextDouble() * sum;
double cumulatedProbabilities = 0.0;
int index = 0;
while (cityIndex == -1 && index < probabilities.Length)
{
if (cumulatedProbabilities <= rand && rand <= cumulatedProbabilities + probabilities[index])
{
cityIndex = index;
}
cumulatedProbabilities += probabilities[index];
index++;
}
return(cityIndex);
}
protected override ZhuEncoding Crossover(IRandom random, ZhuEncoding parent1, ZhuEncoding parent2)
{
parent1 = parent1.Clone() as ZhuEncoding;
parent2 = parent2.Clone() as ZhuEncoding;
ZhuEncoding child = parent2.Clone() as ZhuEncoding;
if (parent1.Length != parent2.Length)
{
return(child);
}
int breakPoint = random.Next(child.Length);
int i = breakPoint;
int predecessor = breakPoint - 1;
if (predecessor < 0)
{
predecessor = predecessor + child.Length;
}
while (i != predecessor)
{
if (i == breakPoint)
{
child[i] = parent1[i];
Swap(parent2, parent2[i], parent1[i]);
}
if (ProblemInstance.GetDistance(
child[i] + 1, parent1[(i + 1) % child.Length] + 1, child)
<
ProblemInstance.GetDistance(
child[i] + 1, parent2[(i + 1) % child.Length] + 1, child))
{
child[(i + 1) % child.Length] = parent1[(i + 1) % child.Length];
Swap(parent2, parent2[(i + 1) % child.Length], parent1[(i + 1) % child.Length]);
}
else
{
child[(i + 1) % child.Length] = parent2[(i + 1) % child.Length];
Swap(parent1, parent1[(i + 1) % child.Length], parent2[(i + 1) % child.Length]);
}
i = (i + 1) % child.Length;
}
return(child);
}
private GVREncoding Crossover(IRandom random, GVREncoding parent1, GVREncoding parent2)
{
GVREncoding child = parent1.Clone() as GVREncoding;
Tour tour = parent2.Tours[random.Next(parent2.Tours.Count)];
int breakPoint1 = random.Next(tour.Stops.Count);
int length = random.Next(1, tour.Stops.Count - breakPoint1 + 1);
List <int> subroute = tour.Stops.GetRange(breakPoint1, length);
//remove duplicates
List <Tour> toBeRemoved = new List <Tour>();
foreach (Tour route in child.Tours)
{
foreach (int city in subroute)
{
route.Stops.Remove(city);
}
if (route.Stops.Count == 0)
{
toBeRemoved.Add(route);
}
}
foreach (Tour route in toBeRemoved)
{
child.Tours.Remove(route);
}
//choose nearest customer
double minDistance = -1;
int customer = -1;
for (int i = 1; i <= ProblemInstance.Cities.Value; i++)
{
if (!subroute.Contains(i))
{
double distance = ProblemInstance.GetDistance(subroute[0], i, child);
if (customer == -1 || distance < minDistance)
{
customer = i;
minDistance = distance;
}
}
}
//insert
if (customer != -1)
{
Tour newTour;
int newPosition;
child.FindCustomer(customer, out newTour, out newPosition);
newTour.Stops.InsertRange(newPosition + 1, subroute);
}
else
{
//special case -> only one tour, whole tour has been chosen as subroute
child = parent1.Clone() as GVREncoding;
}
return(child);
}
protected override ZhuEncoding Crossover(IRandom random, ZhuEncoding parent1, ZhuEncoding parent2)
{
List <int> p1 = new List <int>(parent1);
List <int> p2 = new List <int>(parent2);
ZhuEncoding child = parent2.Clone() as ZhuEncoding;
if (parent1.Length != parent2.Length)
{
return(child);
}
int breakPoint = random.Next(child.Length);
int i = breakPoint;
int predecessor = breakPoint - 1;
if (predecessor < 0)
{
predecessor = predecessor + child.Length;
}
int parent1Index = i;
int parent2Index = i;
while (i != predecessor)
{
if (i == breakPoint)
{
child[i] = p1[parent1Index];
p1.Remove(child[i]);
if (parent1Index >= p1.Count)
{
parent1Index = 0;
}
p2.Remove(child[i]);
if (parent2Index >= p2.Count)
{
parent2Index = 0;
}
}
if (ProblemInstance.GetDistance(
child[i] + 1, p1[parent1Index] + 1, child)
<
ProblemInstance.GetDistance(
child[i] + 1, p2[parent2Index] + 1, child))
{
child[(i + 1) % child.Length] = p1[parent1Index];
}
else
{
child[(i + 1) % child.Length] = p2[parent2Index];
}
p1.Remove(child[(i + 1) % child.Length]);
if (parent1Index >= p1.Count)
{
parent1Index = 0;
}
p2.Remove(child[(i + 1) % child.Length]);
if (parent2Index >= p2.Count)
{
parent2Index = 0;
}
i = (i + 1) % child.Length;
}
return(child);
}