public override Move GenerateMove(Board board, ManualResetEvent cancel)
{
XmlDocument moveDocument = null;
XmlNode movesNode = null, moveNode = null;
XmlAttribute movePlayerNode = null, moveSourceNode = null, moveDestinationNode = null, moveValue = null;
moveDocument = new XmlDocument();
movesNode = moveDocument.CreateElement("PotentialMoves");
moveDocument.AppendChild(movesNode);
int bestValue = int.MinValue;
int possibleBestValue = int.MinValue;
Move generatedMove = null;
foreach(Point source in board.GetValidSourcePieces())
{
foreach(Point destination in board.GetValidDestinationPieces(source))
{
moveNode = moveDocument.CreateElement("Move");
movesNode.AppendChild(moveNode);
movePlayerNode = moveDocument.CreateAttribute("Player");
moveNode.Attributes.Append(movePlayerNode);
movePlayerNode.Value = board.CurrentPlayer.ToString();
moveSourceNode = moveDocument.CreateAttribute("Source");
moveNode.Attributes.Append(moveSourceNode);
moveSourceNode.Value = source.ToString();
moveDestinationNode = moveDocument.CreateAttribute("Destination");
moveNode.Attributes.Append(moveDestinationNode);
moveDestinationNode.Value = destination.ToString();
Board nextMoveBoard = ((Board)board.Clone());
nextMoveBoard.MovePiece(source, destination);
possibleBestValue = this.MinimaxAB(nextMoveBoard, board.CurrentPlayer, false, 1,
int.MinValue, int.MaxValue, moveNode);
moveValue = moveDocument.CreateAttribute("Value");
moveNode.Attributes.Append(moveValue);
moveValue.Value = possibleBestValue.ToString();
if(possibleBestValue > bestValue || (possibleBestValue >= bestValue && generatedMove == null))
{
bestValue = possibleBestValue;
generatedMove = new Move(board.CurrentPlayer, source, destination);
}
}
}
string moveFileName = Guid.NewGuid().ToString("n") + ".xml";
moveDocument.Save(moveFileName);
if(this.debugWriter != null)
{
this.debugWriter.WriteLine(
string.Format("Best value for move {0}: {1} ", generatedMove.Print(), bestValue));
Board nextMoveBoard = (Board)board.Clone();
nextMoveBoard.MovePiece(generatedMove.Source, generatedMove.Destination);
this.debugWriter.WriteLine(
string.Format("Evaluation of board for move {0}: {1} ", generatedMove.Print(),
this.Evaluate(nextMoveBoard, board.CurrentPlayer) * -1));
}
return generatedMove;
}
private int MinimaxAB(Board board, Player currentPlayer, bool isMax, int depth, int alpha, int beta, XmlNode parentMoveNode)
{
XmlNode moveNode = null;
XmlAttribute movePlayerNode = null, moveSourceNode = null, moveDestinationNode = null, moveValue = null;
int evaluation = 0;
if(depth >= DepthLimit || board.WinningPlayer != Player.None)
{
evaluation = this.Evaluate(board, currentPlayer);
if(board.CurrentPlayer != Player.None && board.CurrentPlayer != currentPlayer)
{
evaluation *= -1;
}
else if(board.CurrentPlayer == Player.None && board.WinningPlayer != currentPlayer)
{
evaluation *= -1;
}
}
else
{
int nextEvaluation = 0;
foreach(Point source in board.GetValidSourcePieces())
{
foreach(Point destination in board.GetValidDestinationPieces(source))
{
moveNode = parentMoveNode.OwnerDocument.CreateElement("Move");
parentMoveNode.AppendChild(moveNode);
movePlayerNode = parentMoveNode.OwnerDocument.CreateAttribute("Player");
moveNode.Attributes.Append(movePlayerNode);
movePlayerNode.Value = board.CurrentPlayer.ToString();
moveSourceNode = parentMoveNode.OwnerDocument.CreateAttribute("Source");
moveNode.Attributes.Append(moveSourceNode);
moveSourceNode.Value = source.ToString();
moveDestinationNode = parentMoveNode.OwnerDocument.CreateAttribute("Destination");
moveNode.Attributes.Append(moveDestinationNode);
moveDestinationNode.Value = destination.ToString();
Board nextMoveBoard = (Board)board.Clone();
nextMoveBoard.MovePiece(source, destination);
int newDepth = depth;
nextEvaluation = this.MinimaxAB(nextMoveBoard, currentPlayer, !isMax, ++newDepth, alpha, beta, moveNode);
moveValue = parentMoveNode.OwnerDocument.CreateAttribute("Value");
moveNode.Attributes.Append(moveValue);
moveValue.Value = nextEvaluation.ToString();
if(alpha > beta)
{
break;
}
else if(isMax == false && nextEvaluation < beta)
{
beta = nextEvaluation;
}
else if(isMax == true && nextEvaluation > alpha)
{
alpha = nextEvaluation;
}
}
if(alpha > beta)
{
break;
}
}
if(isMax == true)
{
evaluation = alpha;
}
else
{
evaluation = beta;
}
}
return evaluation;
}
public void GetEvaluationValueForInProgressGameAboutToBeLost()
{
Board board = new Board();
AlphaBetaPruningEngine engine = new AlphaBetaPruningEngine();
Move nextMove = engine.GenerateMove(board.Clone() as Board, new ManualResetEvent(false));
// The problem is that ABP was doing 0,3 to 4,3 in 0.2.0.0, which causes a loss.
Assert.IsFalse((nextMove.Source == new Point(0, 3) && nextMove.Destination == new Point(4, 3)), "The next move is invalid.");
}
