private double DistanceBetweenGlowworms(Glowworm glowworm1, Glowworm glowworm2)
{
double distanceSum = 0;
for (int i = 0; i < this.ranges.Count; i++)
{
distanceSum += Math.Pow(glowworm1.Position.Axis.Values[i] - glowworm2.Position.Axis.Values[i], 2);
}
return(Math.Sqrt(distanceSum));
}
public List <TSP.Chromosome> Select(List <TSP.Chromosome> population, int number)
{
if (Math.Sqrt(population.Count) % 1 != 0)
{
throw new Exception("Non-square chromosomes sizes not supported for glowworm selection.");
}
int arraySize = (int)Math.Sqrt(population.Count);
float initialLuciferin = 0.5f;
List <Glowworm> glowworms = new List <Glowworm>(); //the glowworms that traverse the population for the selection process
// 1. Transform population into 2D array
// Randomize our population
population.Shuffle();
Chromosome[,] solutionSpace = new Chromosome[arraySize, arraySize];
float glowwormRange = arraySize / 3f;
// Assign population to our 2D array
Stack <Chromosome> solutionsToAdd = new Stack <Chromosome>(population);
for (int i = 0; i <= solutionSpace.GetUpperBound(0); i++)
{
for (int j = 0; j <= solutionSpace.GetUpperBound(1); j++)
{
solutionSpace[i, j] = solutionsToAdd.Pop();
}
}
// 2. Distribute glowworms randomly across a 2d plane
int glowwormCount = (population.Count + 9) / 10;
for (int i = 0; i < glowwormCount; i++)
{
glowworms.Add(new Glowworm(i, ThreadSafeRandom.CurrentThreadRandom.Next(arraySize), ThreadSafeRandom.CurrentThreadRandom.Next(arraySize), initialLuciferin));
}
// 3. Repeat 4-5 for x steps for x movement phases
for (int i = 0; i < population.Count / 4; i++)
{
//Perform initial luciferin update
foreach (Glowworm glowworm in glowworms)
{
glowworm.Luciferin += solutionSpace[glowworm.X, glowworm.Y].GetFitness();
}
bool movementOccured = false;
// 4. Glowworm movement
foreach (Glowworm currentGlowworm in glowworms)
{
Glowworm closestGlowworm = null;
double closestDistance = double.MaxValue;
//Find glowworm in range with the highest luciferin value
foreach (Glowworm neighbouringGlowworm in glowworms)
{
// Make sure that the current glowworm isn't the same as the neighbour
if (!(currentGlowworm.ID == neighbouringGlowworm.ID || (currentGlowworm.X == neighbouringGlowworm.X && currentGlowworm.Y == neighbouringGlowworm.Y)))
{
// check if neighbouring glowworm has higher luciferin value
if (neighbouringGlowworm.Luciferin > currentGlowworm.Luciferin)
{
//check if neighbouring glowworm is in range and closer than current closest glowworm (using euclidean distance)
double distance = Math.Sqrt(Math.Pow(currentGlowworm.X - neighbouringGlowworm.X, 2) + Math.Pow(currentGlowworm.Y - neighbouringGlowworm.Y, 2));
if (distance <= glowwormRange && distance < closestDistance)
{
closestDistance = distance;
closestGlowworm = neighbouringGlowworm;
}
}
}
}
if (closestGlowworm != null)
{
// If a glowworn with a higher luciferin was found in range move towards it
currentGlowworm.MoveTowardsNeighbour(closestGlowworm.X, closestGlowworm.Y);
movementOccured = true;
}
}
if (!movementOccured)
{
break;
}
}
// Find best solutions
List <Chromosome> traversedSolutions = new List <Chromosome>();
for (int i = 0; i < solutionSpace.GetUpperBound(0); i++)
{
for (int j = 0; j < solutionSpace.GetUpperBound(1); j++)
{
if (solutionSpace[i, j].GetCost() != -1)
{
traversedSolutions.Add(solutionSpace[i, j]);
}
}
}
return(traversedSolutions.OrderByDescending(s => s.GetFitness()).Take(number).ToList());
}
