applyFitnessSharingToResults method

void applyFitnessSharingToResults(Generation<P, G, R> generation)

Iterates over members and raises their fitness score according to their uniqueness.

If fitnessSharing is false, doesn't do anything.

Algorithm as described in Jeffrey Horn: The Nature of Niching, pp 20-21. http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.33.8352&rep=rep1&type=pdf

Implementation

void applyFitnessSharingToResults(Generation<P, G, R> generation) {
  if (fitnessSharing == false) return;

  for (final ph in generation.members) {
    final similars =
        generation.getSimilarPhenotypes(ph, fitnessSharingRadius);
    var nicheCount = 0.0;
    for (final other in similars) {
      // TODO: stop computing hamming distance twice (in getSimilarPhenotypes
      //       and here)
      final distance = ph.computeHammingDistance(other);
      nicheCount +=
          1 - math.pow(distance / fitnessSharingRadius, fitnessSharingAlpha);
    }
    // The algorithm is modified - we multiply the result instead of
    // dividing it. (Because we count 0.0 as perfect fitness. The smaller
    // the result number, the fitter the phenotype.)
    ph.resultWithFitnessSharingApplied = ph.result!.evaluate() * nicheCount;
  }
}