private NeatGenome <T> CreateGenomeInner(
NeatGenome <T> parent1,
NeatGenome <T> parent2,
IRandomSource rng)
{
// Resolve a flag that determines if *all* disjoint genes from the secondary parent will be included in the child genome, or not.
// This approach is from SharpNEAT v2.x and is preserved to act as baseline in v4.x, but better strategies may exist.
bool includeSecondaryParentGene = DiscreteDistribution.SampleBernoulli(rng, _secondaryParentGeneProbability);
// Enumerate over the connection genes in both parents.
foreach (var geneIndexPair in EnumerateParentGenes(parent1.ConnectionGenes, parent2.ConnectionGenes))
{
// Create a connection gene based on the current position in both parents.
ConnectionGene <T>?connGene = CreateConnectionGene(
parent1.ConnectionGenes, parent2.ConnectionGenes,
geneIndexPair.Item1, geneIndexPair.Item2,
includeSecondaryParentGene, rng);
if (connGene.HasValue)
{ // Attempt to add the gene to the child genome we are building.
_connGeneListBuilder.TryAddGene(connGene.Value);
}
}
// Convert the genes to the structure required by NeatGenome.
ConnectionGenes <T> connGenes = _connGeneListBuilder.ToConnectionGenes();
// Create and return a new genome.
return(_genomeBuilder.Create(
_genomeIdSeq.Next(),
_generationSeq.Peek,
connGenes));
}
private ConnectionGene <T>?CreateConnectionGene(
ConnectionGenes <T> connGenes1,
ConnectionGenes <T> connGenes2,
int idx1, int idx2,
IRandomSource rng)
{
// Select gene at random if it is present on both parents.
if (-1 != idx1 && -1 != idx2)
{
if (rng.NextBool())
{
return(CreateConnectionGene(connGenes1, idx1));
}
else
{
return(CreateConnectionGene(connGenes2, idx2));
}
}
// Use the primary parent's gene if it has one.
if (-1 != idx1)
{
return(CreateConnectionGene(connGenes1, idx1));
}
// Otherwise use the secondary parent's gene stochastically.
if (DiscreteDistribution.SampleBernoulli(rng, _secondaryParentGeneProbability))
{
return(CreateConnectionGene(connGenes2, idx2));
}
return(null);
}