ec.gp.koza

Class FullBuilder

java.lang.Object

ec.gp.GPNodeBuilder

ec.gp.koza.KozaBuilder

ec.gp.koza.FullBuilder

All Implemented Interfaces:

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

public class FullBuilder
extends KozaBuilder

FullBuilder is a GPNodeBuilder which implements the FULL tree building method described in Koza I/II.

GROW works by choosing a random integer d between minDepth and maxDepth, inclusive. It then grows a full tree of depth d.

Actually, claiming to implement the Koza I/II approach is a bit of a fib -- Koza's original code is somewhat ad-hoc. In the Koza approach, d is chosen in a kind of round-robin fashion rather than at random, if RAMPED HALF/HALF is used. Also, for all three algorithms (RAMPED HALF/HALF, GROW, FULL), the algorithm will not generate a tree consisting of a single terminal, unless forced to.

This implementation instead follows lil-gp's approach, which is to choose d at random from between minDepth and maxDepth, inclusive, and to allow trees consisting of single terminals.

Determining what various algorithms do is a little confusing, mostly because the source code for lil-gp and Koza don't actually quite do what they claim. The table below lists the depth values actually used (counting nodes, rather than edges, for depth). It's probably not what you had expected!

	Koza I Min	Koza I Max	Koza II Min	Koza II Max	lil-gp Min	lil-gp Max	ECJ Min	ECJ Max
GROW (mut)	5	5	5	5			5	5
GROW (new)	7	7	6? 7?	6? 7?	3	7	5	5
FULL (new)	7	7	6? 7?	6? 7?	3	7
HALF (new)	2	6	2	5? 6?	3	7	2	6

The table cell is empty when that parameter is not defined by the system by default. Koza II has two values each because of a possible typo in the text -- while page 656 gives one maximum, page 671 gives another. Note the odd fact that in Koza I/II GROW and FULL have effectively one-deeper tree values than HALF does, even though they use the same code parameters! This is because of a quirk in Koza's code.

This algorithm ignores requestedSize, so no pipelines can ask it to grow a tree of a specific fixed size. The algorithm also ignores any user-provided size distributions.

Parameters

base.min-depth int >= 1	(smallest "maximum" depth the builder may use for building a tree. 2 is the default.)
base.max-depth int >= base.min-depth	(largest "maximum" depth the builder may use for building a tree. 6 is the default.)

Default Base
gp.koza.full

See Also:

Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
static java.lang.String	P_FULLBUILDER

Fields inherited from class ec.gp.koza.KozaBuilder

maxDepth, minDepth, P_MAXDEPTH, P_MINDEPTH

Fields inherited from class ec.gp.GPNodeBuilder

CHECK_BOUNDARY, maxSize, minSize, NOSIZEGIVEN, P_MAXSIZE, P_MINSIZE, P_NUMSIZES, P_SIZE, sizeDistribution

Constructor Summary

Constructors

Constructor and Description
FullBuilder()

Method Summary

Modifier and Type	Method and Description
Parameter	defaultBase() Returns the default base for this prototype.
GPNode	newRootedTree(EvolutionState state, GPType type, int thread, GPNodeParent parent, GPFunctionSet set, int argposition, int requestedSize)

Methods inherited from class ec.gp.koza.KozaBuilder

setup

Methods inherited from class ec.gp.GPNodeBuilder

canPick, clone, pickSize

Methods inherited from class java.lang.Object

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

Field Detail

P_FULLBUILDER

public static final java.lang.String P_FULLBUILDER

See Also:

Constant Field Values

Constructor Detail

FullBuilder

public FullBuilder()

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(...).

newRootedTree

public GPNode newRootedTree(EvolutionState state,
                            GPType type,
                            int thread,
                            GPNodeParent parent,
                            GPFunctionSet set,
                            int argposition,
                            int requestedSize)

Specified by:

newRootedTree in class GPNodeBuilder