/// <summary>
/// Tell how different are 2 genomes. This is used in speciation.
/// </summary>
/// <returns>A normalized float.</returns>
public static float GeneticDistance(NEATConfig config, Genome genome1, Genome genome2)
{
var distance = 0f;
var comparisonInfo = new GenomeComparisonInfo(genome1, genome2);
var genesCountInBiggest = Mathf.Max(genome1.Genes.Count, genome2.Genes.Count);
var disjointDist = comparisonInfo.Disjoint.Count * config.speciesCompatibility.disjointImpact;
var excessDist = comparisonInfo.Excess.Count * config.speciesCompatibility.excessImpact;
distance += disjointDist / genesCountInBiggest;
distance += excessDist / genesCountInBiggest;
float totalWeightDif = 0;
foreach (var gene in comparisonInfo.Matching)
{
var weight1 = Mathf.Abs(genome1.GetGene(gene).Weight);
var weight2 = Mathf.Abs(genome2.GetGene(gene).Weight);
var diff = Mathf.Abs(weight1 - weight2) / Mathf.Max(weight1, weight2);
totalWeightDif += diff;
}
distance += totalWeightDif / comparisonInfo.Matching.Count * config.speciesCompatibility.weightMeanDifCoef;
distance /= config.speciesCompatibility.TotalImpactSum;
return(distance);
}
/// <summary>
/// Create a new offspring by combining the 2 parents' genes.
/// The Matching genes are already randomly chosen from parent1 or p2.
/// </summary>
/// <returns>A fresh Genome (not mutated yet).</returns>
public static Genome Crossover(NEATConfig config, Genome parent1, Genome parent2)
{
var fittestParent = (parent1.Fitness > parent2.Fitness) ? parent1 : parent2;
var genesToInherit = new List <Gene>(fittestParent.Genes.Count);
var comparisonInfo = new GenomeComparisonInfo(parent1, parent2);
// The matching genes are chosen randomly from target1 or target2
genesToInherit.AddRange(comparisonInfo.Matching.Select(x => new Gene(x)));
// Add the disjoint genes from the fittests.
genesToInherit.AddRange(comparisonInfo.Disjoint.Where(x => x.Value == fittestParent)
.Select(x => new Gene(x.Key)));
// Add the excess genes from the fittests.
genesToInherit.AddRange(comparisonInfo.Excess.Where(x => x.Value == fittestParent)
.Select(x => new Gene(x.Key)));
return(new Genome(fittestParent, genesToInherit));
}
