@Override public void performIteration(PSO algorithm) { delegate.performIteration(algorithm); Topology<Particle> topology = algorithm.getTopology(); // calculate vAvg Vector avgV = Vectors.mean( Lists.transform( topology, new Function<Particle, Vector>() { @Override public Vector apply(Particle f) { return (Vector) f.getVelocity(); } })); Vector.Builder builder = Vector.newBuilder(); for (Numeric n : avgV) { if (Math.abs(n.doubleValue()) > vMax.getParameter()) { builder.add(vMax.getParameter()); } else { builder.add(n); } } avgV = builder.build(); // mutation Particle gBest = Topologies.getBestEntity(topology, new SocialBestFitnessComparator()); Particle mutated = gBest.getClone(); Vector pos = (Vector) gBest.getBestPosition(); final Bounds bounds = pos.boundsOf(0); pos = pos.plus( avgV.multiply( new Supplier<Number>() { @Override public Number get() { return distribution.getRandomNumber() * bounds.getRange() + bounds.getLowerBound(); } })); mutated.setCandidateSolution(pos); mutated.calculateFitness(); if (gBest.getBestFitness().compareTo(mutated.getFitness()) < 0) { gBest.getProperties().put(EntityType.Particle.BEST_FITNESS, mutated.getBestFitness()); gBest.getProperties().put(EntityType.Particle.BEST_POSITION, mutated.getBestPosition()); } }