net.sourceforge.cilib.pso.velocityprovider.GCVelocityProvider Maven / Gradle / Ivy
/** __ __
* _____ _/ /_/ /_ Computational Intelligence Library (CIlib)
* / ___/ / / / __ \ (c) CIRG @ UP
* / /__/ / / / /_/ / http://cilib.net
* \___/_/_/_/_.___/
*/
package net.sourceforge.cilib.pso.velocityprovider;
import net.sourceforge.cilib.algorithm.AbstractAlgorithm;
import net.sourceforge.cilib.controlparameter.ConstantControlParameter;
import net.sourceforge.cilib.controlparameter.ControlParameter;
import net.sourceforge.cilib.entity.Topologies;
import net.sourceforge.cilib.entity.comparator.SocialBestFitnessComparator;
import net.sourceforge.cilib.math.random.generator.Rand;
import net.sourceforge.cilib.problem.solution.Fitness;
import net.sourceforge.cilib.problem.solution.InferiorFitness;
import net.sourceforge.cilib.pso.PSO;
import net.sourceforge.cilib.pso.particle.Particle;
import net.sourceforge.cilib.type.types.Bounds;
import net.sourceforge.cilib.type.types.container.Vector;
/**
* An implementation of the Guaranteed Convergence PSO algorithm. The GCPSO is a simple extension
* to the normal PSO algorithm and the modifications to the algorithm is implemented as
* a simple {@link VelocityProvider}.
*
* References:
*
-
* F. van den Bergh and A. Engelbrecht, "A new locally convergent particle swarm optimizer,"
* in Proceedings of IEEE Conference on Systems, Man and Cybernetics,
* (Hammamet, Tunisia), Oct. 2002.
*
-
* F. van den Bergh, "An Analysis of Particle Swarm Optimizers,"
* PhD thesis, Department of Computer Science,
* University of Pretoria, South Africa, 2002.
*
*
* TODO: The Rho value should be a vector to hold the rho value for each dimension!
*
* It is very important to realise the importance of the rho values. rho
* determines the local search size of the global best particle and depending on the domain
* this could result in poor performance if the rho value is too small or too large depending
* on the specified problem domain. For example, a rho value of 1.0 is not a good
* value within problems which have a domain that spans [0,1]
*/
public class GCVelocityProvider implements VelocityProvider {
private static final long serialVersionUID = 5985694749940610522L;
private VelocityProvider delegate;
private ControlParameter inertiaWeight;
private ControlParameter rhoLowerBound;
private ControlParameter rho;
private int successCount;
private int failureCount;
private int successCountThreshold;
private int failureCountThreshold;
private Fitness oldFitness;
private ControlParameter rhoExpandCoefficient;
private ControlParameter rhoContractCoefficient;
/**
* Create an instance of the GC Velocity Update strategy.
*/
public GCVelocityProvider() {
this.delegate = new StandardVelocityProvider();
this.inertiaWeight = ConstantControlParameter.of(0.729844);
this.rho = ConstantControlParameter.of(1.0);
this.rhoLowerBound = ConstantControlParameter.of(1.0e-323);
this.successCount = 0;
this.failureCount = 0;
this.successCountThreshold = 15;
this.failureCountThreshold = 5;
this.oldFitness = InferiorFitness.instance();
this.rhoExpandCoefficient = ConstantControlParameter.of(1.2);
this.rhoContractCoefficient = ConstantControlParameter.of(0.5);
}
/**
* Copy constructor. Copy the given instance.
* @param copy The instance to copy.
*/
public GCVelocityProvider(GCVelocityProvider copy) {
this.delegate = copy.delegate.getClone();
this.inertiaWeight = copy.inertiaWeight.getClone();
this.rho = copy.rho.getClone();
this.rhoLowerBound = copy.rhoLowerBound.getClone();
this.successCount = copy.successCount;
this.failureCount = copy.failureCount;
this.successCountThreshold = copy.successCountThreshold;
this.failureCountThreshold = copy.failureCountThreshold;
this.oldFitness = copy.oldFitness.getClone();
this.rhoExpandCoefficient = copy.rhoExpandCoefficient.getClone();
this.rhoContractCoefficient = copy.rhoContractCoefficient.getClone();
}
/**
* {@inheritDoc}
*/
@Override
public GCVelocityProvider getClone() {
return new GCVelocityProvider(this);
}
/**
* {@inheritDoc}
*/
@Override
public Vector get(Particle particle) {
PSO pso = (PSO) AbstractAlgorithm.get();
final Particle globalBest = Topologies.getBestEntity(pso.getTopology(), new SocialBestFitnessComparator());
Vector result;
if (particle == globalBest) {
final Vector velocity = (Vector) particle.getVelocity();
final Vector position = (Vector) particle.getPosition();
final Vector globalGuide = (Vector) particle.getGlobalGuide();
Vector.Builder builder = Vector.newBuilder();
for (int i = 0; i < velocity.size(); ++i) {
double component = -position.doubleValueOf(i) + globalGuide.doubleValueOf(i)
+ this.inertiaWeight.getParameter() * velocity.doubleValueOf(i)
+ this.rho.getParameter() * (1 - 2 * Rand.nextDouble());
builder.add(component);
}
this.oldFitness = particle.getFitness().getClone(); // Keep a copy of the old Fitness object - particle.calculateFitness() within the IterationStrategy resets the fitness value
result = builder.build();
}
else {
result = this.delegate.get(particle);
}
updateControlParameters(particle);
return result;
}
/**
* Updates certain control parameters for this velocity provider.
* @param particle
*/
public void updateControlParameters(Particle particle) {
// Remember NOT to reset the rho value to 1.0
PSO pso = (PSO) AbstractAlgorithm.get();
if (particle == Topologies.getBestEntity(pso.getTopology(), new SocialBestFitnessComparator())) {
Fitness newFitness = particle.getFitnessCalculator().getFitness(particle);
if (!newFitness.equals(oldFitness)) {
this.failureCount = 0;
this.successCount++;
} else {
this.successCount = 0;
this.failureCount++;
}
updateRho((Vector) particle.getPosition());
return;
}
this.failureCount = 0;
this.successCount = 0;
}
/**
* Update the rho value.
* @param position
*/
private void updateRho(Vector position) { // the Rho value is problem and dimension dependent
double tmp = 0.0;
Bounds component = position.boundsOf(0);
double average = (component.getUpperBound() - component.getLowerBound()) / this.rhoExpandCoefficient.getParameter();
if (this.successCount >= this.successCountThreshold) {
tmp = this.rhoExpandCoefficient.getParameter() * this.rho.getParameter();
}
if (this.failureCount >= this.failureCountThreshold) {
tmp = this.rhoContractCoefficient.getParameter() * this.rho.getParameter();
}
if (tmp <= this.rhoLowerBound.getParameter()) {
tmp = this.rhoLowerBound.getParameter();
}
if (tmp >= average) {
tmp = average;
}
this.rho = ConstantControlParameter.of(tmp);
}
public VelocityProvider getDelegate() {
return this.delegate;
}
public void setDelegate(VelocityProvider delegate) {
this.delegate = delegate;
}
/**
* Get the lower-bound value for rho.
* @return The lower-bound value for rho.
*/
public ControlParameter getRhoLowerBound() {
return this.rhoLowerBound;
}
/**
* Set the lower-bound value for rho.
* @param rhoLowerBound The lower-bound to set.
*/
public void setRhoLowerBound(ControlParameter rhoLowerBound) {
this.rhoLowerBound = rhoLowerBound;
}
/**
* Get the current value for rho.
* @return The current value for rho.
*/
public ControlParameter getRho() {
return this.rho;
}
/**
* Set the value for rho.
* @param rho The value to set.
*/
public void setRho(ControlParameter rho) {
this.rho = rho;
}
/**
* Get the count of success threshold.
* @return The success threshold.
*/
public int getSuccessCountThreshold() {
return this.successCountThreshold;
}
/**
* Set the threshold of success count value.
* @param successCountThreshold The value to set.
*/
public void setSuccessCountThreshold(int successCountThreshold) {
this.successCountThreshold = successCountThreshold;
}
/**
* Get the count of failure threshold.
* @return The failure threshold.
*/
public int getFailureCountThreshold() {
return this.failureCountThreshold;
}
/**
* Set the count of failure threshold.
* @param failureCountThreshold The value to set.
*/
public void setFailureCountThreshold(int failureCountThreshold) {
this.failureCountThreshold = failureCountThreshold;
}
/**
* Get the coefficient value for rho expansion.
* @return The expansion coefficient value.
*/
public ControlParameter getRhoExpandCoefficient() {
return this.rhoExpandCoefficient;
}
/**
* Set the value of the coefficient of expansion.
* @param rhoExpandCoefficient The value to set.
*/
public void setRhoExpandCoefficient(ControlParameter rhoExpandCoefficient) {
this.rhoExpandCoefficient = rhoExpandCoefficient;
}
/**
* Get the coefficient value for rho contraction.
* @return The contraction coefficient value.
*/
public ControlParameter getRhoContractCoefficient() {
return this.rhoContractCoefficient;
}
/**
* Set the contraction coefficient value.
* @param rhoContractCoefficient The value to set.
*/
public void setRhoContractCoefficient(ControlParameter rhoContractCoefficient) {
this.rhoContractCoefficient = rhoContractCoefficient;
}
/**
* Set the inertia weight value.
* @param inertiaWeight The value to set.
*/
public void setInertiaWeight(ControlParameter inertiaWeight) {
this.inertiaWeight = inertiaWeight;
}
}