/**
* Compute the collective offspring the entire species (the sum of all
* individual's offspring) is assigned skim is fractional offspring left
* over from a previous subspecies that was counted. These fractional parts
* are kept until they add up to 1
*/
public double CountOffspring(double skim)
{
ExpectedOffspring = 0;
const double y1 = 1.0;
double r2 = skim;
int n2 = 0;
foreach (var t in Individuals.Cast <NEATIndividual>())
{
double x1 = t.ExpectedOffspring;
int n1 = (int)(x1 / y1);
double r1 = x1 - ((int)(x1 / y1) * y1);
n2 = n2 + n1;
r2 = r2 + r1;
if (r2 >= 1.0)
{
n2 = n2 + 1;
r2 = r2 - 1.0;
}
}
ExpectedOffspring = n2;
return(r2);
}
/**
* Remove the individuals from current subspecies who have been mark as
* eliminate the remain individuals will be allow to reproduce
*/
public void RemovePoorFitnessIndividuals()
{
// create a new list, contain the non eliminate individuals
IList <Individual> remainIndividuals = new List <Individual>();
foreach (var ind in Individuals.Cast <NEATIndividual>())
{
if (!ind.Eliminate)
{
remainIndividuals.Add(ind);
}
}
Individuals = remainIndividuals;
}
/**
* Adjust the fitness of the individuals within this subspecies. We will use
* the adjusted fitness to determine the expected offsprings within each
* subspecies.
*/
public void AdjustFitness(IEvolutionState state, int dropoffAge, double ageSignificance)
{
int ageDebt = (Age - AgeOfLastImprovement + 1) - dropoffAge;
if (ageDebt == 0)
{
ageDebt = 1;
}
foreach (NEATIndividual ind in Individuals.Cast <NEATIndividual>())
{
// start to adjust the fitness with age information
ind.AdjustedFitness = ind.Fitness.Value;
// Make fitness decrease after a stagnation point dropoffAge
// Added an if to keep species pristine until the dropoff point
if (ageDebt >= 1)
{
ind.AdjustedFitness = ind.AdjustedFitness * 0.01;
}
// Give a fitness boost up to some young age (niching)
// The age-significance parameter is a system parameter
// If it is 1, then young species get no fitness boost
if (Age <= 10)
{
ind.AdjustedFitness = ind.AdjustedFitness * ageSignificance;
}
// Do not allow negative fitness
if (ind.AdjustedFitness < 0.0)
{
ind.AdjustedFitness = 0.0001;
}
// Share fitness with the species
// This is the explicit fitness sharing, where the the original
// fitness
// are dividing by the number of individuals in the species.
// By using this, a species cannot afford to become too big even if
// many of its
// individual perform well
ind.AdjustedFitness = ind.AdjustedFitness / Individuals.Count;
}
}