org.jgap
Class FitnessFunction

java.lang.Object
  org.jgap.FitnessFunction

All Implemented Interfaces:

java.io.Serializable, java.lang.Cloneable, ICloneable

Direct Known Subclasses:

AbstractChangeFitnessFunction, CachedFitnessFunction, CoinsEnergyFitnessFunction, CoinsExampleFitnessFunction, DynamicMutationFitnessFunction, KnapsackFitnessFunction, LMSFitnessFunction, MaxFunction, MaxFunction, MaxFunction, MaximizingFunctionFitnessFunction, MinimizingMakeChangeFitnessFunction, SalesmanFitnessFunction, SampleFitnessFunction, SampleFitnessFunction, SampleFitnessFunction, SampleFitnessFunction, TruthTableFitnessFunction

public abstract class FitnessFunction
extends java.lang.Object
implements java.io.Serializable, ICloneable

Fitness functions are used to determine how optimal a particular solution is relative to other solutions. This abstract class should be extended and the evaluate() method implemented. The fitness function is given a Chromosome to evaluate and should return a positive double that reflects its fitness value. The higher the value, the more fit the Chromosome. The actual range of fitness values isn't important (other than the fact that they must be positive doubles): it's the relative difference as a percentage that tends to determine the success or failure of a Chromosome. So in other words, two Chromosomes with respective fitness values of 1 and 100 have the same relative fitness to each other as two Chromosomes with respective fitness values of 10 and 1000 (in each case, the first is 1% as fit as the second).

Note: Two Chromosomes with equivalent sets of genes should always be assigned the same fitness value by any implementation of this interface.

Since:

1.0

See Also:

Serialized Form

Field Summary

static double	DELTA
static double	NO_FITNESS_VALUE

Constructor Summary

FitnessFunction()

Method Summary

java.lang.Object	clone() Please override in your implementations!
protected abstract double	evaluate(IChromosome a_subject) Determine the fitness of the given Chromosome instance.
double	getFitnessValue(IChromosome a_subject) Retrieves the fitness value of the given Chromosome.
double	getLastComputedFitnessValue()

Methods inherited from class java.lang.Object

equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

NO_FITNESS_VALUE

public static final double NO_FITNESS_VALUE

See Also:

Constant Field Values

DELTA

public static final double DELTA

See Also:

Constant Field Values

Constructor Detail

FitnessFunction

public FitnessFunction()

Method Detail

getFitnessValue

public double getFitnessValue(IChromosome a_subject)

Retrieves the fitness value of the given Chromosome. The fitness value will be a positive double.

Parameters:

a_subject - the Chromosome for which to compute and return the fitness value

Returns:

the fitness value of the given Chromosome

Since:

2.0 (until 1.1: return type int)

getLastComputedFitnessValue

public double getLastComputedFitnessValue()

Returns:

the last fitness value computed via method getFitnessValue( Chromosome), or NO_FITNES_VALUE if the former method has not been called yet

Since:

2.4

evaluate

protected abstract double evaluate(IChromosome a_subject)

Determine the fitness of the given Chromosome instance. The higher the return value, the more fit the instance. This method should always return the same fitness value for two equivalent Chromosome instances.

Parameters:

a_subject - the Chromosome instance to evaluate

Returns:

positive double reflecting the fitness rating of the given Chromosome. Note that if a non-positive double is returned, a RuntimeException should be generated

Since:

2.0 (until 1.1: return type int)

clone

public java.lang.Object clone()

Please override in your implementations!

Specified by:

clone in interface ICloneable

Overrides:

clone in class java.lang.Object

Returns:

deep clone of the current instance

Since:

3.2