ec.gp.koza
Class KozaNodeSelector

java.lang.Object
  extended by 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:

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

DefaultBase
gp.koza.ns

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

Field Summary
protected  GPNodeGatherer gatherer
          Used internally to look for a node.
 int nodes
          The number of nodes in the tree, -1 if unknown.
 float 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
           
 float rootProbability
          The probability the root must be chosen
 float terminalProbability
          The probability a terminal must be chosen
 int terminals
          The number of terminals in the tree, -1 if unknown.
 
Constructor Summary
KozaNodeSelector()
           
 
Method Summary
 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, finalize, 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 float rootProbability
The probability the root must be chosen


terminalProbability

public float terminalProbability
The probability a terminal must be chosen


nonterminalProbability

public float 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.


gatherer

protected GPNodeGatherer gatherer
Used internally to look for a node. This is threadsafe as long as an instance of KozaNodeSelector is used by only one thread.

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:

Implementations.

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