/// <summary>
/// Handles iterating a generation of the population.
/// All evaluations must have been done by this point.
/// </summary>
/// <param name="rando">A random number generator.</param>
public void Epoch(Random rando)
{
foreach (var spec in Species)
{
spec.SetChampions();
}
SortSpeciesByChampionFitness();
Genome generationChampion = Species.Last().Fitness.Champion;
if (generationChampion.Fitness.Score >= Fitness.ChampionScore)
{
GenerationPrime = Generation;
}
Fitness.GenerationalChampion = generationChampion;
Dictionary <Species, int> ExpectedChildren = FindExpectedChildren();
foreach (var spec in Species)
{
int numberOfParents = (int)Math.Floor(spec.Size() * Const.SurvivalThresh + 1);
spec.SortGenomesByFitness();
spec.Genomes.RemoveRange(0, spec.Size() - numberOfParents);
}
List <Genome> nextGenerationGenomes = new List <Genome>();
foreach (var specCountPair in ExpectedChildren)
{
nextGenerationGenomes.AddRange(specCountPair.Key.Reproduce(specCountPair.Value, GenerationalInnovations, Species, rando));
}
ClearParentGeneration();
SpeciateNewGeneration(nextGenerationGenomes);
RemoveDeadSpecies();
ResetSpeciesTemplates();
AgeSpecies();
Generation++;
HistoricalInnovations.AddRange(GenerationalInnovations);
GenerationalInnovations.Clear();
}
/// <summary>
/// Finds the expected children of each species.
/// </summary>
/// <returns>A dictionary of each species that will definitely have children.</returns>
private Dictionary <Species, int> FindExpectedChildren()
{
Dictionary <Species, int> expectedChildren = new Dictionary <Species, int>();
Species mostExpectingSpecies = null;
int totalChildren = 0;
//Original NEAT calls this delta-coding.
//Original NEAT does not check this first. It overrides the 'else' statement logic. Seemed unneccessary.
if (Generation - GenerationPrime >= Const.PopulationDropoffGenerations)
{
GenerationPrime = Generation;
int halfPopulationSize = TargetPopulationSize / 2;
if (Species.Count == 1)
{
expectedChildren[Species.Last()] = TargetPopulationSize;
totalChildren = TargetPopulationSize;
Species.Last().AgePrime = Species.Last().Age;
mostExpectingSpecies = Species.Last();
}
else
{
expectedChildren[Species.Last()] = halfPopulationSize;
Species.Last().AgePrime = Species.Last().Age;
mostExpectingSpecies = Species.Last();
expectedChildren[Species[Species.Count - 1]] = halfPopulationSize;
Species[Species.Count - 1].AgePrime = Species[Species.Count - 1].Age;
totalChildren = 2 * halfPopulationSize;
}
}
else
{
if (Generation % Const.SpeciesStagnationEpochCycle == 0)
{
foreach (var spec in Species)
{
if (spec.Age > Const.OverTheHillThresh)
{
spec.OnDeathBed = true;
break;
}
}
}
double sumOfTotalAdjustedScore = 0.0;
foreach (var spec in Species)
{
spec.AdjustFitness();
sumOfTotalAdjustedScore += spec.Fitness.TotalAdjustedScore;
}
int mostExpected = 0;
foreach (var spec in Species)
{
int children = 0;
//Warning: There is no check in the original NEAT that handles this case.
if (sumOfTotalAdjustedScore != 0)
{
children = (int)(spec.Fitness.TotalAdjustedScore * TargetPopulationSize / sumOfTotalAdjustedScore);
}
if (children > 0)
{
expectedChildren.Add(spec, children);
totalChildren += children;
}
if (children > mostExpected)
{
mostExpectingSpecies = spec;
mostExpected = children;
}
}
}
if (totalChildren > 0)
{
expectedChildren[mostExpectingSpecies] += TargetPopulationSize - totalChildren;
}
else
{
expectedChildren.Add(Species.Last(), TargetPopulationSize);
}
return(expectedChildren);
}