public void MakeBestMove(out int X, out int Y, Board board)
{
this.originalBoard = board;
AlphaBeta(-50000, 50000, 0, 7, originalBoard.currentPlayer, board);
//PVS(-50000, 50000, 0, 6, originalBoard.currentPlayer, board);
X = this.bestMoveX;
Y = this.bestMoveY;
}
protected int AlphaBeta(int alpha, int beta, int pass, int depth, int player, Board previousBoard)
{
int subBestX = -1;
int subBestY = -1;
int bestValue = MIN_VALUE;
if (depth <= 0)
return Evaluation(previousBoard,player);
//Try every possible position
for( int i=0; i<8; i++ )
{
for (int j = 0; j < 8; j++)
{
Board nextBoard = previousBoard.CloneBoard().FlipPiece(i, j, false, player);
if (nextBoard != null)
{
int value = -AlphaBeta(-beta, -alpha, 0, depth - 1, -player, nextBoard);
if (value > beta)
return value;
if (value > bestValue)
{
bestValue = value;
subBestX = i;
subBestY = j;
if(value > alpha)
alpha = value;
}
}
}
}
if (bestValue <= MIN_VALUE)
{
if (pass == 0)
{
//here may be needed to be modified
//since the game is over, the player can win then the weight should be
//very large to assure he can win
return previousBoard.ComputeScore(player) * 100;
}
//DoPassMove();
bestValue = -AlphaBeta(-beta, -alpha, 1, depth,-player,previousBoard);
//UnDoPassMove();
}
bestMoveX = subBestX;
bestMoveY = subBestY;
return bestValue;
}
public Board CloneBoard()
{
Board resultBoard = new Board();
resultBoard.currentPlayer = this.currentPlayer;
resultBoard.noOfPieces = this.noOfPieces;
resultBoard.gameMode = this.gameMode;
resultBoard.startPlayer = this.startPlayer;
for (int i = 0; i < 8; i++)
for (int j = 0; j < 8; j++)
{
resultBoard.positions[i, j].color = this.positions[i, j].color;
resultBoard.positions[i, j].weight = this.positions[i, j].weight;
}
return resultBoard;
}
/// <summary>
/// Place a piece on (direcX, direcY). (-2, -2) indicates initial play by AI
/// </summary>
/// <param name="X"></param>
/// <param name="Y"></param>
/// <returns>0: Successfully placed; 1: Game Ended; 2: No possible Move for current player; 3: Error in AI</returns>
public int Play(int direcX, int direcY, out string result, bool isAI)
{
if (direcX != -2 || direcY != -2)
{
if (positions[direcX, direcY].color == 0)
{
Board previous = this.CloneBoard();
if (FlipPiece(direcX, direcY, false, currentPlayer) != null)
{
lastPlayX = direcX;
lastPlayY = direcY;
if (noOfPieces == 64)
{
result = EndGame();
return 1;
}
if (!isAI)
this.previousBoard = previous;
}
else if (isAI)
{
result = "Error: AI try to put in invalid place " + direcX.ToString() + "/" + direcY.ToString();
return 3;
}
else
{
result = "";
return -1;
}
}
else if (!isAI)
{
result = "";
return -1;
}
}
int statusCode = -1;
int noPossibleMoves = GetNoPossibleMoves(currentPlayer);
if (noPossibleMoves == 0)
{
currentPlayer = -currentPlayer;
noPossibleMoves = GetNoPossibleMoves(currentPlayer);
if (noPossibleMoves == 0)
{
result = EndGame();
return 1;
}
result = currentPlayer == 1 ? "No possible move for black player. White player plays again" : "No possible move for white player. Black player plays again";
statusCode = 2;
}
else
{
result = currentPlayer == 1 ? "White player playing..." : "Black player playing...";
statusCode = 0;
}
if (IsCurrentPlayerAI() && gameMode == 1 && (statusCode == 0 || statusCode == 2) && isAI)
{
statusCode = AIPlay(out result);
if (statusCode == -1)
{
result = "Error: AI failed to move";
statusCode = 3;
}
//else
//{
// result = currentPlayer == 1 ? "White player playing..." : "Black player playing...";
// statusCode = 0;
//}
}
return statusCode;
}
protected int ComputeWeight(Board board,int player)
{
int result = 0;
foreach (Position pos in board.positions)
{
result += (pos.color * pos.weight);
}
return player == 1 ? result : -result;
}
protected int Evaluation(Board board,int player)
{
//int num = 0;
//for (int i = 0; i < 8; i++)
//{
// for (int j = 0; j < 8; j++)
// {
// if (board.positions[i, j].color != 0)
// num++;
// }
//}
//if(num > 10)
//{
//W_MOBILITY = 1;
// W_WEIGTH = 3;
//}
return W_WEIGTH * ComputeWeight(board, player) + W_SELF_MOBILITY * Mobility(player);// -W_OPP_MOBILITY * Mobility(-player);
}