// TODO -> Find different ways to create initial population
// TODO-> always add in next gen
private void CreateInitialPopulation()
{
var citiesSet = _tspInstance.CitiesSet;
if (citiesSet == null)
{
throw new Exception("Cities cannot be null");
}
if (citiesSet.Count < 1)
{
throw new Exception("Cities must at least have a length of 3.");
}
// copying cities into an array starting from index 1
var cities = citiesSet.Keys.ToArray(); // TODO -> Should I have an array in tsp instance instead ??? to avoid to array ?
var elements = new int[cities.Length - 1];
for (int i = 1; i < cities.Length; i++)
{
elements[i - 1] = cities[i];
}
for (int i = 0; i < Population.PopulationSize; i++)
{
// fisher-yates-shuffle O(n)
for (int j = elements.Length - 1; j > 0; j--)
{
var swapIndex = Random.Next(j + 1);
var tmp = elements[j];
elements[j] = elements[swapIndex];
elements[swapIndex] = tmp;
}
// adding to population
var chromosome = new Chromosome <int>(elements);
CalculateFitness(chromosome);
Population.AddChromosome(i, chromosome);
}
// prepare for next evolution
Population.SetNextGeneration();
SelectionOperator.SetNextGeneration();
}
private void CreateNextGeneration()
{
var startingIndex = UsingElitism ? NumberOfElite : 0;
if (UsingElitism)
{
Population.SortByFitness();
for (int i = 0; i < NumberOfElite; i++)
{
Population.AddChromosome(i, Population.Chromosomes[i]);
}
startingIndex = NumberOfElite;
}
var populationSize = Population.PopulationSize;
for (int i = startingIndex; i < populationSize; i++)
{
// TODO -> Should I make sure that both parents are different ??
// selection operation
var fatherChromosome = SelectionOperator.PopulationSelection(Population);
var motherChromosome = SelectionOperator.PopulationSelection(Population);
// TODO -> return more than one child always!!!
// crossover operation
var childChromosome = CrossoverOperator.Crossover(fatherChromosome, motherChromosome); // TODO -> some crossovers can return more than one child
// mutate operation
MutationOperator.Mutate(childChromosome);
// add child chromsome to the next generation population
CalculateFitness(childChromosome);
Population.AddChromosome(i, childChromosome);
}
// prepare for next evolution
Population.SetNextGeneration();
SelectionOperator.SetNextGeneration();
Generation++;
}