examples.knapsack
Class KnapsackFitnessFunction

java.lang.Object
  org.jgap.FitnessFunction
      examples.knapsack.KnapsackFitnessFunction

All Implemented Interfaces:

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

public class KnapsackFitnessFunction
extends FitnessFunction

Fitness function for the knapsack example.

Since:

2.3

See Also:

Serialized Form

Field Summary

static double

MAX_BOUND

Fields inherited from class org.jgap.FitnessFunction

DELTA, NO_FITNESS_VALUE

Constructor Summary

KnapsackFitnessFunction(double a_knapsackVolume)

Method Summary

protected double	computeItemNumberPenalty(double a_maxFitness, int a_items) Calculates the penalty to apply to the fitness value based on the amount of items in the solution.
double	evaluate(IChromosome a_subject) Determine the fitness of the given Chromosome instance.
static int	getNumberOfItemsAtGene(IChromosome a_potentialSolution, int a_position) Retrieves the number of items represented by the given potential solution at the given gene position.
static int	getTotalNumberOfItems(IChromosome a_potentialSolution) Returns the total number of items represented by all of the genes in the given potential solution.
static double	getTotalVolume(IChromosome a_potentialSolution) Calculates the total amount of change (in cents) represented by the given potential solution and returns that amount.
protected double	volumeDifferenceBonus(double a_maxFitness, double a_volumeDifference) Bonus calculation of fitness value.

Methods inherited from class org.jgap.FitnessFunction

clone, getFitnessValue, getLastComputedFitnessValue

Methods inherited from class java.lang.Object

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

Field Detail

MAX_BOUND

public static final double MAX_BOUND

See Also:

Constant Field Values

Constructor Detail

KnapsackFitnessFunction

public KnapsackFitnessFunction(double a_knapsackVolume)

Method Detail

evaluate

public 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.

Specified by:

evaluate in class FitnessFunction

Parameters:

a_subject - the Chromosome instance to evaluate

Returns:

a positive double reflecting the fitness rating of the given Chromosome

Since:

2.3

volumeDifferenceBonus

protected double volumeDifferenceBonus(double a_maxFitness,
                                       double a_volumeDifference)

Bonus calculation of fitness value.

Parameters:

a_maxFitness - maximum fitness value appliable

a_volumeDifference - volume difference in ccm for the items problem

Returns:

bonus for given volume difference

Since:

2.3

computeItemNumberPenalty

protected double computeItemNumberPenalty(double a_maxFitness,
                                          int a_items)

Calculates the penalty to apply to the fitness value based on the amount of items in the solution.

Parameters:

a_maxFitness - upper boundary for fitness value possible

a_items - number of items in the solution

Returns:

a penalty for the fitness value based on the number of items

Since:

2.3

getTotalVolume

public static double getTotalVolume(IChromosome a_potentialSolution)

Calculates the total amount of change (in cents) represented by the given potential solution and returns that amount.

Parameters:

a_potentialSolution - the potential solution to evaluate

Returns:

the total amount of change (in cents) represented by the given solution

Since:

2.3

getNumberOfItemsAtGene

public static int getNumberOfItemsAtGene(IChromosome a_potentialSolution,
                                         int a_position)

Retrieves the number of items represented by the given potential solution at the given gene position.

Parameters:

a_potentialSolution - the potential solution to evaluate

a_position - the gene position to evaluate

Returns:

the number of items represented by the potential solution at the given gene position

Since:

2.3

getTotalNumberOfItems

public static int getTotalNumberOfItems(IChromosome a_potentialSolution)

Returns the total number of items represented by all of the genes in the given potential solution.

Parameters:

a_potentialSolution - the potential solution to evaluate

Returns:

the total number of items represented by the given Chromosome

Since:

2.3