net.sourceforge.cilib.pso.iterationstrategies.SynchronousIterationStrategy Maven / Gradle / Ivy

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/**           __  __
 *    _____ _/ /_/ /_    Computational Intelligence Library (CIlib)
 *   / ___/ / / / __ \   (c) CIRG @ UP
 *  / /__/ / / / /_/ /   http://cilib.net
 *  \___/_/_/_/_.___/
 */
package net.sourceforge.cilib.pso.iterationstrategies;

import net.sourceforge.cilib.algorithm.population.AbstractIterationStrategy;
import net.sourceforge.cilib.pso.PSO;
import net.sourceforge.cilib.pso.particle.Particle;
import fj.F;

/**
 * Implementation of the synchronous iteration strategy for PSO.
 */
public class SynchronousIterationStrategy extends AbstractIterationStrategy {

    private static final long serialVersionUID = 6617737228912852220L;

    /**
     * {@inheritDoc}
     */
    @Override
    public SynchronousIterationStrategy getClone() {
        return this;
    }

    /**
     * This is an Synchronous strategy:
     *
     * 
     *   For all particles:
     *   
     *     Update the particle velocity
     *     Update the particle position
     *   
     *   For all particles:
     *   
     *     Calculate the particle fitness
     *     For all particles in the current particle's neighbourhood:
     *     
     *       Update the neighbourhood best
     *     
     *   
     * 
     *
     * @param pso The {@link PSO} to have an iteration applied.
     */
    @Override
    public void performIteration(final PSO pso) {
        final fj.data.List topology = pso.getTopology();

        final F first = new F() {
			@Override
			public Particle f(Particle current) {
				current.updateVelocity();
	            current.updatePosition();

	            boundaryConstraint.enforce(current);
	            return current;
			}
        };

        final F second = new F() {
        	public Particle f(Particle current) {
        		current.calculateFitness();
        		for (Particle other : pso.getNeighbourhood().f(topology, current)) {
        			if (current.getSocialFitness().compareTo(other.getNeighbourhoodBest().getSocialFitness()) > 0) {
        				other.setNeighbourhoodBest(current);
        			}
        		}

        		return current;
        	}
        };

        pso.setTopology(topology.map(first).map(second));
    }
}