jcgp.backend.population

Class Node

java.lang.Object

jcgp.backend.population.Node

All Implemented Interfaces:

Connection, Mutable

public class Node
extends java.lang.Object
implements Mutable, Connection

Nodes make up the main part of the chromosome, where the actual functions are evolved. Each node contains a function and a number of connections. The node outputs the result of performing its function on the values of its connections. Nodes therefore implement both Mutable and Connection since they can be mutated but also connected to. Nodes are constructed with a fixed number of connections (determined by the maximum arity of the function set) and must be reinstantiated if the experiment arity changes.

When mutating a node, it is easiest to use mutate(). Alternatively, you may also perform a specific mutation using setConnection(...) and setFunction(...).

Author:

Eduardo Pedroni

Constructor Summary

Constructors

Constructor and Description
Node(Chromosome chromosome, int row, int column) Constructs a new instance of Node with the specified parameters.

Method Summary

Modifier and Type	Method and Description
boolean	copyOf(Mutable element) Asserts if the specified element is a copy of the elements this is called on. This method returns true if and only if: the elements being compared are not the same instance; the connections of the compared elements are not the same instance; the elements have the same function (in the case of Node); the grid position of the elements themselves are the same; the grid position of all equivalent connections are the same; The relationship computed by this method is: symmetric: a.copyOf(b) == b.copyOf(a); not reflexive: a.copyOf(a) returns false; not transitive: if a.copyOf(b) is true and b.copyOf(c) is true, a.copyOf(c) is not necessarily true since it is possible that a == c.
int	getColumn()
Connection	getConnection(int index)
Function	getFunction()
int	getRow()
java.lang.Object	getValue() Compute and return the value of this connection.
void	initialise(Function newFunction, Connection... newConnections) Initialises the node with the specified values.
void	mutate() This method performs an arbitrary mutation on the Mutable.
void	setConnection(int index, Connection newConnection) This method sets the indexed connection to the specified new connection.
void	setFunction(Function newFunction) Sets the node function.
java.lang.String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

Node

public Node(Chromosome chromosome,
            int row,
            int column)

Constructs a new instance of Node with the specified parameters. Nodes must contain their own row and column for ease of copying.

Parameters:

chromosome - the chromosome this node belongs to.

row - the node's row.

column - the node's column.

Method Detail

initialise

public void initialise(Function newFunction,
                       Connection... newConnections)

Initialises the node with the specified values. The number of connections passed as argument must be exactly the same as the experiment arity, or an IllegalArgumentException will be thrown.

Parameters:

newFunction - the node function to set.

newConnections - the node connections to set.

getColumn

public int getColumn()

Returns:

this node's column.

getRow

public int getRow()

Returns:

this node's row.

getFunction

public Function getFunction()

Returns:

this node's function.

setFunction

public void setFunction(Function newFunction)

Sets the node function.

Parameters:

newFunction - the new function to set.

getConnection

public Connection getConnection(int index)

Parameters:

index - the connection to return.

Returns:

the indexed connection.

setConnection

public void setConnection(int index,
                          Connection newConnection)

This method sets the indexed connection to the specified new connection. If the given connection is null or disrespects levels back, it is discarded and no connections are changed.

Parameters:

index - the connection index to set.

newConnection - the Connection to connect to.

copyOf

public boolean copyOf(Mutable element)

Description copied from interface: Mutable

Asserts if the specified element is a copy of the elements this is called on.
This method returns true if and only if:

• the elements being compared are not the same instance;
• the connections of the compared elements are not the same instance;
• the elements have the same function (in the case of Node);
• the grid position of the elements themselves are the same;
• the grid position of all equivalent connections are the same;

The relationship computed by this method is:

• symmetric: a.copyOf(b) == b.copyOf(a);
• not reflexive: a.copyOf(a) returns false;
• not transitive: if a.copyOf(b) is true and b.copyOf(c) is true, a.copyOf(c) is not necessarily true since it is possible that a == c.

Specified by:

copyOf in interface Mutable

Parameters:

element - the mutable element to compare to.

Returns:

true if element is a copy of this element.

getValue

public java.lang.Object getValue()

Description copied from interface: Connection

Compute and return the value of this connection. In the case of inputs no computation is necessary, this simply returns the value the input is set to. In the case of nodes, the value is computed based on the node's function and the value of its own connections.

Specified by:

getValue in interface Connection

Returns:

the connection's value.

mutate

public void mutate()

Description copied from interface: Mutable

This method performs an arbitrary mutation on the Mutable.

In the case of nodes, this chooses to mutate a function or connection fairly, and carries out the required mutation by using the node's own reference to chromosome.

In the case of outputs, this simply picks a random connection to serve as the source - any connection is allowed.

Specified by:

mutate in interface Mutable

toString

public java.lang.String toString()

Overrides:

toString in class java.lang.Object