public IGeneration Evolve(Func <IGenome, double> getFitness)
{
IGeneration nextGeneration = new Generation(new Population());
Population.Evaluate(getFitness);
int spareOffspring = 0;
Population.Species.ForEach(s =>
{
s.Age++;
if (s.LastImprovementAge > SpeciesParameters.DropOffAge)
{
spareOffspring += s.ExpectedOffspring;
s.ExpectedOffspring = 0;
}
});
if (spareOffspring > 0)
{
Population.BestSpecies.ExpectedOffspring += spareOffspring;
}
// Compensate for floating point inaccuracy
while (Population.ExpectedOffspring < Population.Genomes.Count)
{
Population.BestSpecies.ExpectedOffspring++;
}
// Create the Offspring for each species
List <ISpecies> populationSpecies = Population.Species.ToList();
populationSpecies.ForEach(s =>
{
bool championSelected = false;
IEnumerable <IGenome> speciesGenomes = s.NaturalSelect();
// Create the offspring
Enumerable.Range(0, s.ExpectedOffspring).ToList().ForEach(i =>
{
IGenome offspring = null;
if (s.ExpectedOffspring > GenerationParameters.ChampionCopyMinimumGenomes && !championSelected)
{
offspring = speciesGenomes.OrderByDescending(p => p.Fitness / s.Genomes.Count).First();
championSelected = true;
}
else if (new Random().NextDouble() < GenerationParameters.MutateOnlyProbability || s.Genomes.Count == 1)
{
// Mutate
IGenome candidate = GetRandomGenomeBiasFitness(speciesGenomes);
Mutate(candidate, GetSoftenFactor(candidate.Fitness, speciesGenomes));
offspring = candidate;
}
else
{
IGenome parent = null;
IGenome mate = null;
// Mate
if (new Random().NextDouble() < GenerationParameters.InterspeciesBreedingRate)
{
// Interspecies mating
parent = GetRandomGenomeBiasFitness(speciesGenomes);
mate = GetRandomGenomeBiasFitness(speciesGenomes);
offspring = parent.Breed(mate);
}
else
{
// Mate outside of species
ISpecies speciesMate = GetRandomSpeciesBiasFitness(Population.Species.Where(sp => sp != s));
parent = GetRandomGenomeBiasFitness(speciesGenomes);
mate = GetRandomGenomeBiasFitness(speciesMate.NaturalSelect());
offspring = parent.Breed(mate);
}
if (new Random().NextDouble() < GenerationParameters.MutateOffspringProbability || parent == mate)
{
Mutate(offspring, GetSoftenFactor(Math.Max(parent.Fitness, mate.Fitness), speciesGenomes));
}
}
if (offspring != null)
{
IGenome genome = offspring.Copy();
// Speciate the offspring against the current population
// This way we can see what species need to be carried over into the next generation population
Population.Speciate(genome);
ISpecies species = Population.Species.First(sp => sp.Id == genome.SpeciesId).CopyWithoutGenomes();
if (!nextGeneration.Population.Species.Contains(species, new SpeciesComparer()))
{
nextGeneration.Population.Species.Add(species);
}
nextGeneration.Population.Species.First(sp => sp.Id == species.Id).Genomes.Add(genome);
nextGeneration.Population.Genomes.Add(genome);
}
});
});
nextGeneration.FittestGenome = Population.Genomes.OrderByDescending(p => p.Fitness).First();
return(nextGeneration);
}
