public MOVE GetBestMove(IGameTree <MOVE> state)
{
if (!state.IsAITurn)
{
throw new InvalidOperationException("It is not the AI's turn");
}
else if (state.ValidMoves.Count == 0)
{
throw new InvalidOperationException("No valid moves");
}
else
{
var best = default(MOVE);
var bestScore = double.NegativeInfinity;
foreach (var move in state.ValidMoves)
{
var successorState = state.MakeMove(move);
var successorStateScore = ScoreState(successorState, this._ply - 1);
if (successorStateScore > bestScore)
{
best = move;
bestScore = successorStateScore;
}
}
return(best);
}
}
private double ScoreOpponentState(IGameTree <MOVE> state, int ply, double minimum, double maximum)
{
Debug.Assert(ply >= 0);
Debug.Assert(!state.IsAITurn);
if (ply == 0 || state.ValidMoves.Count == 0)
{
return(state.Score);
}
else
{
var worst = double.PositiveInfinity;
foreach (var validMove in state.ValidMoves)
{
var successorState = state.MakeMove(validMove);
var successorStateScore = ScoreState(successorState, ply - 1, minimum, worst);
if (successorStateScore < worst)
{
worst = successorStateScore;
if (worst <= minimum)
{
return(worst);
}
}
}
return(worst);
}
}
private double ScoreAIState(IGameTree <MOVE> state, int ply, double minimum, double maximum)
{
Debug.Assert(ply >= 0);
Debug.Assert(state.IsAITurn);
if (state.ValidMoves.Count == 0)
{
return(state.Score);
}
else
{
var best = double.NegativeInfinity;
foreach (var validMove in state.ValidMoves)
{
var successorState = state.MakeMove(validMove);
var successorStateScore = ScoreState(successorState, ply - 1, best, maximum);
if (successorStateScore > best)
{
best = successorStateScore;
if (best >= maximum)
{
return(best);
}
}
}
return(best);
}
}
private double ScoreState(IGameTree <MOVE> state, int ply)
{
if (state.IsAITurn)
{
return(ScoreAIState(state, ply));
}
else
{
return(ScoreOpponentState(state, ply));
}
}
private double ScoreState(IGameTree <MOVE> state, int ply, double minimum, double maximum)
{
if (state.IsAITurn)
{
return(ScoreAIState(state, ply, minimum, maximum));
}
else
{
return(ScoreOpponentState(state, ply, minimum, maximum));
}
}
private double ScoreOpponentState(IGameTree <MOVE> state, int ply)
{
Debug.Assert(ply >= 0);
Debug.Assert(!state.IsAITurn);
if (ply == 0 || state.ValidMoves.Count == 0)
{
return(state.Score);
}
else
{
return(state.ValidMoves.Min(move => ScoreState(state.MakeMove(move), ply - 1)));
}
}
/**
* Set player who opens the game.
* called by parallel thread in a server game
*/
public override void SetStarter(bool b)
{
if (b)
{
// computer starts
if (VERBOSE)
{
Debug.WriteLine("Computer starts");
}
m_humanColor = IController.BLACK;
m_humanStarts = false;
}
else
{
// human starts
if (VERBOSE)
{
Debug.WriteLine("Human starts");
}
m_humanColor = IController.WHITE;
m_humanStarts = true;
}
// refresh gui: must be called after beginning player have been chosen
m_view.PrepareBoard();
// create new game tree
m_gameTree = new GameTree();
if (b)
{
// computer will open the game
m_gameTree.Create(TREEDEPTH, null);
if (VERBOSE)
{
Debug.WriteLine("\tgame tree created; tree size: " + m_gameTree.Size());
}
}
}
public void Add(string move, IGameTree <string> child)
{
_children.Add(move, child);
}
public LazyGameTree(IGameTree <MOVE> gameTree)
{
Debug.Assert(gameTree != null);
this._originalTree = gameTree;
}
