Class ArtificialGamePosition

java.lang.Object

gametree.ArtificialGamePosition

All Implemented Interfaces:

IGamePosition<ArtificialGamePosition>, Serializable

public class ArtificialGamePosition
extends Object
implements IGamePosition<ArtificialGamePosition>, Serializable

Represents a game position in an artificial game tree. This class models both adversarial and non-adversarial game trees with a fixed branching factor and integer valued nodes. Each node is uniquely identified by its name, which is derived from its position in the tree.

The tree is characterised by a ArtificialGamePosition.Settings object, which defines parameters such as the branching factor (ArtificialGamePosition.Settings.width), growth factor (ArtificialGamePosition.Settings.growth_factor), and initial range (ArtificialGamePosition.Settings.initial_range). Nodes are generated deterministically based on these settings and a pseudo-random number generator seed, ensuring reproducibility of the tree structure.

This class is designed for use in scenarios where deterministic and reproducible game trees are required, such as in testing game tree search algorithms or simulations.

Version:

1.0

Author:

Pascal Anema

See Also:

• Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	ArtificialGamePosition.Settings	A class that stores the settings for a ArtificialGamePosition tree.

Field Summary

Fields

Modifier and Type	Field	Description
final BigInteger	name	Name of this node which denotes its position in the tree.
final ArtificialGamePosition.Settings	settings	The ArtificialGamePosition.Settings object which characterises the tree this node is from.

Constructor Summary

Constructors

Constructor	Description
ArtificialGamePosition(boolean adversarial, long initial_seed, int width, long initial_range, int num_alts, double growth_factor, double force_relevance_chance)	Gives the root node of the tree characterised by the given parameters.
ArtificialGamePosition(ArtificialGamePosition.Settings settings)	Gives the root node of the tree characterised by the given ArtificialGamePosition.Settings object.

Method Summary

Modifier and Type	Method	Description
long	hash()	This method should be implemented with a hash that still remains different from similar states if a mask is applied to the hash.
double	lowerbound()	The lower-bound value is the lower bound on the game-theoretical mini-max value of this game position.
boolean	maximising()
static long	maxV(long[] values)	Finds the maximum value of an array
static long	minV(long[] values)	Finds the minimum value of an array
List<ArtificialGamePosition>	next()
ArtificialGamePosition	parent()
static long	safeSum(long x, long y)	Sums two values such that the result does not 'overflow' from positive to negative or vice versa.
String	toString()
double	upperbound()	The upper-bound value is the upper bound on the game-theoretical mini-max value of this game position.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Details

settings

public final ArtificialGamePosition.Settings settings

The ArtificialGamePosition.Settings object which characterises the tree this node is from.

name

public final BigInteger name

Name of this node which denotes its position in the tree. Nodes are named after their parent node and their position relative to their sibling nodes. The root node is always named 0.

For example, a node named 100 in a tree with ArtificialGamePosition.Settings.width == 5 has children named 501, 502, 503, 504, and 505.

Constructor Details

ArtificialGamePosition

public ArtificialGamePosition(ArtificialGamePosition.Settings settings)

Gives the root node of the tree characterised by the given ArtificialGamePosition.Settings object.

Parameters:

settings - the ArtificialGamePosition.Settings object which characterises the tree

ArtificialGamePosition

public ArtificialGamePosition(boolean adversarial,
 long initial_seed,
 int width,
 long initial_range,
 int num_alts,
 double growth_factor,
 double force_relevance_chance)

Gives the root node of the tree characterised by the given parameters.

Parameters:

adversarial - ArtificialGamePosition.Settings.adversarial, denotes whether this tree is an adversarial tree or not

initial_seed - ArtificialGamePosition.Settings.initial_seed, denotes a unique tree generation sequence

width - ArtificialGamePosition.Settings.width, has to be greater than or equal to 2

initial_range - ArtificialGamePosition.Settings.initial_range, has to be greater than 0

num_alts - ArtificialGamePosition.Settings.num_alts, has to be greater than or equal to 2

growth_factor - ArtificialGamePosition.Settings.growth_factor, has to be greater than 0

force_relevance_chance - ArtificialGamePosition.Settings.force_relevance_chance, has to be greater than or equal to 0 and smaller than or equal to 1

Method Details

next

public List<ArtificialGamePosition> next()

Specified by:

next in interface IGamePosition<ArtificialGamePosition>

Returns:

The collection of game positions directly reachable by moves from the current player to move in this game position.

upperbound

public double upperbound()

Description copied from interface: IGamePosition

The upper-bound value is the upper bound on the game-theoretical mini-max value of this game position.

For the maximising player this is the best value achievable under perfect play.

For the minimising player this is the worst-case value achievable under perfect play.

Specified by:

upperbound in interface IGamePosition<ArtificialGamePosition>

Returns:

The upper-bound value for this game position

lowerbound

public double lowerbound()

Description copied from interface: IGamePosition

The lower-bound value is the lower bound on the game-theoretical mini-max value of this game position.

For the maximising player this is the minimum value that can be guaranteed under perfect play.

For the minimising player this is the best value achievable under perfect play.

Specified by:

lowerbound in interface IGamePosition<ArtificialGamePosition>

Returns:

The lower-bound value for this game position

maximising

public boolean maximising()

Specified by:

maximising in interface IGamePosition<ArtificialGamePosition>

Returns:

true if the current player-to-move is maximising the score, or false if it is minimising the score.

hash

public long hash()

Description copied from interface: IGamePosition

This method should be implemented with a hash that still remains different from similar states if a mask is applied to the hash. Commonly, a transposition table implementation may only use the first 20 to 26 bits of the hash to use as an index, so the hash should try to minimise collisions regardless of how many bits are included for the index.

Specified by:

hash in interface IGamePosition<ArtificialGamePosition>

Returns:

a 64-bit zobrist hash or other kind of game-state hash that represents this state.

parent

public ArtificialGamePosition parent()

Returns:

The parent of this node. This is required for random access of ArtificialGamePosition objects.

minV

public static long minV(long[] values)

Finds the minimum value of an array

Parameters:

values - the array of values to search

Returns:

the minimum value of the provided values array.

maxV

public static long maxV(long[] values)

Finds the maximum value of an array

Parameters:

values - the array of values to search

Returns:

the maximum value of the provided values array.

safeSum

public static long safeSum(long x,
 long y)

Sums two values such that the result does not 'overflow' from positive to negative or vice versa.

Parameters:

x - some value

y - another value

Returns:

x + y unless overflow or underflow occurs, in which case Long.MAX_VALUE or Long.MIN_VALUE respectively.

toString

public String toString()

Overrides:

toString in class Object