ec.gp.koza

Class KozaNodeSelector

java.lang.Object

ec.gp.koza.KozaNodeSelector

All Implemented Interfaces:

GPNodeSelector, Prototype, Setup, java.io.Serializable, java.lang.Cloneable

public class KozaNodeSelector
extends java.lang.Object
implements GPNodeSelector

KozaNodeSelector is a GPNodeSelector which picks nodes in trees a-la Koza I, with the addition of having a probability of always picking the root. The method divides the range 0.0...1.0 into four probability areas:

• One area specifies that the selector must pick a terminal.
• Another area specifies that the selector must pick a nonterminal (if there is one, else a terminal).
• The third area specifies that the selector pick the root node.
• The fourth area specifies that the selector pick any random node.

The KozaNodeSelector chooses by probability between these four situations. Then, based on the situation it has picked, it selects either a random terminal, nonterminal, root, or arbitrary node from the tree and returns it.

As the selector picks a node, it builds up some statistics information which makes it able to pick a little faster in subsequent passes. Thus if you want to reuse this selector on another tree, you need to call reset() first.

Parameters

base.terminals 0.0 <= double <= 1.0, nonterminals + terminals + root <= 1.0	(the probability we must pick a terminal)
base.nonterminals 0.0 <= double <= 1.0, nonterminals + terminals + root <= 1.0	(the probability we must pick a nonterminal if possible)
base.root 0.0 <= double <= 1.0, nonterminals + terminals + root <= 1.0	(the probability we must pick the root)

DefaultBase
gp.koza.ns

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
int	nodes The number of nodes in the tree, -1 if unknown.
double	nonterminalProbability The probability a nonterminal must be chosen.
int	nonterminals The number of nonterminals in the tree, -1 if unknown.
static java.lang.String	P_NODESELECTOR
static java.lang.String	P_NONTERMINAL_PROBABILITY
static java.lang.String	P_ROOT_PROBABILITY
static java.lang.String	P_TERMINAL_PROBABILITY
double	rootProbability The probability the root must be chosen
double	terminalProbability The probability a terminal must be chosen
int	terminals The number of terminals in the tree, -1 if unknown.

Constructor Summary

Constructors

Constructor and Description
KozaNodeSelector()

Method Summary

Modifier and Type	Method and Description
java.lang.Object	clone() Creates a new individual cloned from a prototype, and suitable to begin use in its own evolutionary context.
Parameter	defaultBase() Returns the default base for this prototype.
GPNode	pickNode(EvolutionState s, int subpopulation, int thread, GPIndividual ind, GPTree tree) Picks a node at random from tree and returns it.
void	reset() Resets the Node Selector before a new series of pickNode() if need be.
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.

Methods inherited from class java.lang.Object

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

Field Detail

P_NODESELECTOR

public static final java.lang.String P_NODESELECTOR

See Also:

Constant Field Values

P_TERMINAL_PROBABILITY

public static final java.lang.String P_TERMINAL_PROBABILITY

See Also:

Constant Field Values

P_NONTERMINAL_PROBABILITY

public static final java.lang.String P_NONTERMINAL_PROBABILITY

See Also:

Constant Field Values

P_ROOT_PROBABILITY

public static final java.lang.String P_ROOT_PROBABILITY

See Also:

Constant Field Values

rootProbability

public double rootProbability

The probability the root must be chosen

terminalProbability

public double terminalProbability

The probability a terminal must be chosen

nonterminalProbability

public double nonterminalProbability

The probability a nonterminal must be chosen.

nonterminals

public int nonterminals

The number of nonterminals in the tree, -1 if unknown.

terminals

public int terminals

The number of terminals in the tree, -1 if unknown.

nodes

public int nodes

The number of nodes in the tree, -1 if unknown.

Constructor Detail

KozaNodeSelector

public KozaNodeSelector()

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(...).

Specified by:

defaultBase in interface Prototype

clone

public java.lang.Object clone()

Description copied from interface: Prototype

Creates a new individual cloned from a prototype, and suitable to begin use in its own evolutionary context.

Typically this should be a full "deep" clone. However, you may share certain elements with other objects rather than clone hem, depending on the situation:

• If you hold objects which are shared with other instances, don't clone them.
• If you hold objects which must be unique, clone them.
• If you hold objects which were given to you as a gesture of kindness, and aren't owned by you, you probably shouldn't clone them.
• DON'T attempt to clone: Singletons, Cliques, or Groups.
• Arrays are not cloned automatically; you may need to clone an array if you're not sharing it with other instances. Arrays have the nice feature of being copyable by calling clone() on them.

Implementations.

• If no ancestor of yours implements clone(), and you have no need to do clone deeply, and you are abstract, then you should not declare clone().
• If no ancestor of yours implements clone(), and you have no need to do clone deeply, and you are not abstract, then you should implement it as follows:

   public Object clone() 
       {
       try
           { 
           return super.clone();
           }
       catch ((CloneNotSupportedException e)
           { throw new InternalError(); } // never happens
       }
          

• If no ancestor of yours implements clone(), but you need to deep-clone some things, then you should implement it as follows:

   public Object clone() 
       {
       try
           { 
           MyObject myobj = (MyObject) (super.clone());
  
           // put your deep-cloning code here...
           }
       catch ((CloneNotSupportedException e)
           { throw new InternalError(); } // never happens
       return myobj;
       } 
          

• If an ancestor has implemented clone(), and you also need to deep clone some things, then you should implement it as follows:

   public Object clone() 
       { 
       MyObject myobj = (MyObject) (super.clone());
  
       // put your deep-cloning code here...
  
       return myobj;
       } 
          

Specified by:

clone in interface Prototype

Overrides:

clone in class java.lang.Object

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

reset

public void reset()

Description copied from interface: GPNodeSelector

Resets the Node Selector before a new series of pickNode() if need be.

Specified by:

reset in interface GPNodeSelector

pickNode

public GPNode pickNode(EvolutionState s,
                       int subpopulation,
                       int thread,
                       GPIndividual ind,
                       GPTree tree)

Description copied from interface: GPNodeSelector

Picks a node at random from tree and returns it. The tree is located in ind, which is located in s.population[subpopulation]. This method will be preceded with a call to reset(); afterwards, pickNode(...) may be called several times for the same tree.

Specified by:

pickNode in interface GPNodeSelector