Package a5.ai

Class Minimax<GameState,Move>

java.lang.Object

a5.ai.Minimax<GameState,Move>

public class Minimax<GameState,Move>
extends Object

Implementation of minimax search with alpha-beta pruning.

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	Minimax.OutOfTime	An exception signifying that the search algorithm ran out of time.

Field Summary

Fields

Modifier and Type	Field	Description
static final int	MAX_TRANSPOSITION_TABLE_SIZE	When to flush the table and start over

Constructor Summary

Constructors

Constructor	Description
Minimax(GameModel<GameState,Move> model)	Create a new minimax AI search engine.

Method Summary

Modifier and Type	Method	Description
void	activateTranspositionTable()	Effect: Turn on the use of a transposition table.
Maybe<Move>	findBestMove(GameState state, int searchTime)	Returns: the best move from the given state that can be found by searching for up to a given amount of time.
int	search(GameState state, int depth, int min, int max)	Returns: the optimal minimax value of the current game state, within the range from min to max.
void	setAlphaBetaPruning(boolean value)	Effect: Set whether alpha-beta pruning is used.
void	setShowSearchInfo(boolean value)	Effect: Set whether search info is printed.

Methods inherited from class java.lang.Object

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

Field Details

MAX_TRANSPOSITION_TABLE_SIZE

public static final int MAX_TRANSPOSITION_TABLE_SIZE

When to flush the table and start over

See Also:

• Constant Field Values

Constructor Details

Minimax

public Minimax(GameModel<GameState,Move> model)

Create a new minimax AI search engine.

Parameters:

model - The model of the game

Method Details

activateTranspositionTable

public void activateTranspositionTable()

Effect: Turn on the use of a transposition table.

setAlphaBetaPruning

public void setAlphaBetaPruning(boolean value)

Effect: Set whether alpha-beta pruning is used. It is turned on by default.

setShowSearchInfo

public void setShowSearchInfo(boolean value)

Effect: Set whether search info is printed. It is turned on by default.

findBestMove

public Maybe<Move> findBestMove(GameState state,
 int searchTime)

Returns: the best move from the given state that can be found by searching for up to a given amount of time. Returns Maybe.none() if there is no legal move.

Parameters:

state - the state to search from

searchTime - the maximum time to search, in milliseconds

search

public int search(GameState state,
 int depth,
 int min,
 int max)
           throws Minimax.OutOfTime

Returns: the optimal minimax value of the current game state, within the range from min to max. The minimax value is computed with a specified search depth, with game states reached when depth is 0 evaluated heuristically. It may search deeper than the specified depth. Checks: min < max Requires: depth >= 0, -WIN <= min, max <= WIN. Throws OutOfTime if the search has run out of time.

Throws:

Minimax.OutOfTime