ec.gp.koza
Class KozaFitness

java.lang.Object
  extended by ec.Fitness
      extended by ec.gp.koza.KozaFitness
All Implemented Interfaces:
Prototype, Setup, java.io.Serializable, java.lang.Cloneable

public class KozaFitness
extends Fitness

KozaFitness is a Fitness which stores an individual's fitness as described in Koza I. Well, almost. In KozaFitness, standardized fitness and raw fitness are considered the same (there are different methods for them, but they return the same thing). Standardized fitness ranges from 0.0 inclusive (the best) to infinity exclusive (the worst). Adjusted fitness converts this, using the formula adj_f = 1/(1+f), into a scale from 0.0 exclusive (worst) to 1.0 inclusive (best). While it's the standardized fitness that is stored, it is the adjusted fitness that is printed out. This is all just convenience stuff anyway; selection methods generally don't use these fitness values but instead use the betterThan and equalTo methods.

Default Base
gp.koza.fitness

Version:
1.0
Author:
Sean Luke
See Also:
Serialized Form

Field Summary
protected  float fitness
          This ranges from 0 (best) to infinity (worst).
 int hits
          This auxillary measure is used in some problems for additional information.
static java.lang.String P_KOZAFITNESS
           
 
Fields inherited from class ec.Fitness
FITNESS_PREAMBLE, P_FITNESS
 
Constructor Summary
KozaFitness()
           
 
Method Summary
 float adjustedFitness()
          Returns the adjusted fitness metric, which recasts the fitness to the half-open interval (0,1], where 1 is ideal and 0 is worst.
 boolean betterThan(Fitness _fitness)
          Should return true if this fitness is clearly better than _fitness; You may assume that _fitness is of the same class as yourself.
 Parameter defaultBase()
          Returns the default base for this prototype.
 boolean equivalentTo(Fitness _fitness)
          Should return true if this fitness is in the same equivalence class as _fitness, that is, neither is clearly better or worse than the other.
 float fitness()
          Returns the adjusted fitness metric, which recasts the fitness to the half-open interval (0,1], where 1 is ideal and 0 is worst.
 java.lang.String fitnessToString()
          Print to a string the fitness in a fashion intended to be parsed in again via readFitness(...).
 java.lang.String fitnessToStringForHumans()
          Print to a string the fitness in a fashion readable by humans, and not intended to be parsed in again.
 boolean isIdealFitness()
          Should return true if this is a good enough fitness to end the run
 float rawFitness()
          Returns the raw fitness metric.
 void readFitness(EvolutionState state, java.io.DataInput dataInput)
          Reads the binary form of an individual from a DataInput.
 void readFitness(EvolutionState state, java.io.LineNumberReader reader)
          Reads in the fitness from a form outputted by fitnessToString() and thus printFitnessForHumans(...).
 void setFitness(EvolutionState state, float _f)
          Deprecated.  
 void setStandardizedFitness(EvolutionState state, float _f)
          Set the standardized fitness in the half-open interval [0.0,infinity) which is defined (NOTE: DIFFERENT FROM fitness()!!!) as 0.0 being the IDEAL and infinity being worse than the worst possible.
 void setup(EvolutionState state, Parameter base)
          Sets up the object by reading it from the parameters stored in state, built off of the parameter base base.
 float standardizedFitness()
          Returns the standardized fitness metric, which is the same as the raw fitness metric in this scheme.
 void writeFitness(EvolutionState state, java.io.DataOutput dataOutput)
          Writes the binary form of an individual out to a DataOutput.
 
Methods inherited from class ec.Fitness
clone, printFitness, printFitness, printFitnessForHumans
 
Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

P_KOZAFITNESS

public static final java.lang.String P_KOZAFITNESS
See Also:
Constant Field Values

fitness

protected float fitness
This ranges from 0 (best) to infinity (worst). Koza leaves the exact definition of rawFitness up to the domain problem, but I define it here as equivalent to the standardized fitness, hence the simple definitions of rawFitness() and standardizedFitness() below.


hits

public int hits
This auxillary measure is used in some problems for additional information. It's a traditional feature of Koza-style GP, and so although I think it's not very useful, I'll leave it in anyway.

Constructor Detail

KozaFitness

public KozaFitness()
Method Detail

defaultBase

public Parameter defaultBase()
Description copied from interface: Prototype
Returns the default base for this prototype. This should generally be implemented by building off of the static base() method on the DefaultsForm object for the prototype's package. This should be callable during setup(...).


setFitness

public final void setFitness(EvolutionState state,
                             float _f)
Deprecated. 

Do not use this function. Use the identical setStandardizedFitness() instead. The reason for the name change is that fitness() returns a differently-defined value than setFitness() sets, ugh.


setStandardizedFitness

public final void setStandardizedFitness(EvolutionState state,
                                         float _f)
Set the standardized fitness in the half-open interval [0.0,infinity) which is defined (NOTE: DIFFERENT FROM fitness()!!!) as 0.0 being the IDEAL and infinity being worse than the worst possible. This is the GP tradition. The fitness() function instead will output the equivalent of Adjusted Fitness.


fitness

public final float fitness()
Returns the adjusted fitness metric, which recasts the fitness to the half-open interval (0,1], where 1 is ideal and 0 is worst. Same as adjustedFitness().

Specified by:
fitness in class Fitness

rawFitness

public final float rawFitness()
Returns the raw fitness metric.


standardizedFitness

public final float standardizedFitness()
Returns the standardized fitness metric, which is the same as the raw fitness metric in this scheme.


adjustedFitness

public final float adjustedFitness()
Returns the adjusted fitness metric, which recasts the fitness to the half-open interval (0,1], where 1 is ideal and 0 is worst. This metric is used when printing the fitness out.


setup

public void setup(EvolutionState state,
                  Parameter base)
Description copied from interface: Prototype
Sets up the object by reading it from the parameters stored in state, built off of the parameter base base. If an ancestor implements this method, be sure to call super.setup(state,base); before you do anything else.

For prototypes, setup(...) is typically called once for the prototype instance; cloned instances do not receive the setup(...) call. setup(...) may be called more than once; the only guarantee is that it will get called at least once on an instance or some "parent" object from which it was ultimately cloned.

Specified by:
setup in interface Prototype
Specified by:
setup in interface Setup
Overrides:
setup in class Fitness

isIdealFitness

public final boolean isIdealFitness()
Description copied from class: Fitness
Should return true if this is a good enough fitness to end the run

Specified by:
isIdealFitness in class Fitness

equivalentTo

public boolean equivalentTo(Fitness _fitness)
Description copied from class: Fitness
Should return true if this fitness is in the same equivalence class as _fitness, that is, neither is clearly better or worse than the other. You may assume that _fitness is of the same class as yourself. For any two fitnesses fit1 and fit2 of the same class, it must be the case that fit1.equivalentTo(fit2) == fit2.equivalentTo(fit1), and that only one of fit1.betterThan(fit2), fit1.equivalentTo(fit2), and fit2.betterThan(fit1) can be true.

Specified by:
equivalentTo in class Fitness

betterThan

public boolean betterThan(Fitness _fitness)
Description copied from class: Fitness
Should return true if this fitness is clearly better than _fitness; You may assume that _fitness is of the same class as yourself. For any two fitnesses fit1 and fit2 of the same class, it must be the case that fit1.equivalentTo(fit2) == fit2.equivalentTo(fit1), and that only one of fit1.betterThan(fit2), fit1.equivalentTo(fit2), and fit2.betterThan(fit1) can be true.

Specified by:
betterThan in class Fitness

fitnessToString

public java.lang.String fitnessToString()
Description copied from class: Fitness
Print to a string the fitness in a fashion intended to be parsed in again via readFitness(...). The fitness and evaluated flag should not be included. The default form simply calls toString(), which is almost certainly wrong, and you'll probably want to override this to something else.

Overrides:
fitnessToString in class Fitness

fitnessToStringForHumans

public java.lang.String fitnessToStringForHumans()
Description copied from class: Fitness
Print to a string the fitness in a fashion readable by humans, and not intended to be parsed in again. The default form simply calls toString(), but you'll probably want to override this to something else.

Overrides:
fitnessToStringForHumans in class Fitness

readFitness

public final void readFitness(EvolutionState state,
                              java.io.LineNumberReader reader)
                       throws java.io.IOException
Description copied from class: Fitness
Reads in the fitness from a form outputted by fitnessToString() and thus printFitnessForHumans(...). The default version of this method exits the program with an "unimplemented" error.

Overrides:
readFitness in class Fitness
Throws:
java.io.IOException

writeFitness

public void writeFitness(EvolutionState state,
                         java.io.DataOutput dataOutput)
                  throws java.io.IOException
Description copied from class: Fitness
Writes the binary form of an individual out to a DataOutput. This is not for serialization: the object should only write out the data relevant to the object sufficient to rebuild it from a DataInput. The default version exits the program with an "unimplemented" error; you should override this.

Overrides:
writeFitness in class Fitness
Throws:
java.io.IOException

readFitness

public void readFitness(EvolutionState state,
                        java.io.DataInput dataInput)
                 throws java.io.IOException
Description copied from class: Fitness
Reads the binary form of an individual from a DataInput. This is not for serialization: the object should only read in the data written out via printIndividual(state,dataInput). The default version exits the program with an "unimplemented" error; you should override this.

Overrides:
readFitness in class Fitness
Throws:
java.io.IOException