Package ec.gp.koza

Class KozaNodeSelector

java.lang.Object
ec.gp.koza.KozaNodeSelector
All Implemented Interfaces:
GPNodeSelector, Prototype, Setup, Serializable, Cloneable
public class KozaNodeSelector extends 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 invalid input: '<'= 1.0		 (the probability we must pick a terminal)
base.nonterminals
0.0 <= double <= 1.0,
nonterminals + terminals + root invalid input: '<'= 1.0		 (the probability we must pick a nonterminal if possible)
base.root
0.0 <= double <= 1.0,
nonterminals + terminals + root invalid input: '<'= 1.0		 (the probability we must pick the root)

DefaultBase
gp.koza.ns

See Also:

  • Field Details

    • P_NODESELECTOR

      public static final String P_NODESELECTOR
      See Also:

    • P_TERMINAL_PROBABILITY

      public static final String P_TERMINAL_PROBABILITY
      See Also:

    • P_NONTERMINAL_PROBABILITY

      public static final String P_NONTERMINAL_PROBABILITY
      See Also:

    • P_ROOT_PROBABILITY

      public static final String P_ROOT_PROBABILITY
      See Also:

    • 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 Details

    • KozaNodeSelector

      public KozaNodeSelector()

  • Method Details

    • 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 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 Populations, or Subpopulation.
      • 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 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