// Return the enemy player for the given player
public Player EnemyPlayer(Side Player)
{
if (Player.isBlack())
{
return(m_WhitePlayer);
}
else
{
return(m_BlackPlayer);
}
}
// Get the best move available to the player
public Move GetBestMove()
{
int alpha, beta;
int depth; // depth to which to do the search
TimeSpan ElapsedTime = new TimeSpan(1); // Total elpased time
Move BestMove = null; // The best move for the current position
// Initialize constants
const int MIN_SCORE = -10000000; // Minimum limit of negative for integer
const int MAX_SCORE = 10000000; // Maximum limit of positive integer
ArrayList TotalMoves = m_Rules.GenerateAllLegalMoves(m_Side); // Get all the legal moves for the current side
// Now we use the Iterative deepening technique to search the best move
// The idea is just simple, we will keep searching in the more and more depth
// as long as we don't time out.
// So, it means that when we have less moves, we can search more deeply and which means
// better chess game.
DateTime ThinkStartTime = DateTime.Now;
int MoveCounter;
Random RandGenerator = new Random();
// Game is near the end, or the current player is under check
if (m_Rules.ChessBoard.GetSideCell(m_Side.type).Count <= 5 || TotalMoves.Count <= 5)
{
m_GameNearEnd = true;
}
// Game is near the end, or the Enemy player is under check
Side EnemySide;
if (m_Side.isBlack())
{
EnemySide = m_Rules.ChessGame.WhitePlayer.PlayerSide;
}
else
{
EnemySide = m_Rules.ChessGame.BlackPlayer.PlayerSide;
}
if (m_Rules.ChessBoard.GetSideCell(m_Side.Enemy()).Count <= 5 || m_Rules.GenerateAllLegalMoves(EnemySide).Count <= 5)
{
m_GameNearEnd = true;
}
m_TotalMovesAnalyzed = 0; // Reset the total moves anazlye counter
for (depth = 1;; depth++) // Keep doing a depth search
{
alpha = MIN_SCORE; // The famous Alpha & Beta are set to their initial values
beta = MAX_SCORE; // at the start of each increasing search depth iteration
MoveCounter = 0; // Initialize the move counter variable
// Loop through all the legal moves and get the one with best score
foreach (Move move in TotalMoves)
{
MoveCounter++;
// Now to get the effect of this move; execute this move and analyze the board
m_Rules.ExecuteMove(move);
move.Score = -AlphaBeta(m_Rules.ChessGame.EnemyPlayer(m_Side).PlayerSide, depth - 1, -beta, -alpha);
m_TotalMovesAnalyzed++; // Increment move counter
m_Rules.UndoMove(move); // undo the move
// If the score of the move we just tried is better than the score of the best move we had
// so far, at this depth, then make this the best move.
if (move.Score > alpha)
{
BestMove = move;
alpha = move.Score;
}
m_Rules.ChessGame.NotifyComputerThinking(depth, MoveCounter, TotalMoves.Count, m_TotalMovesAnalyzed, BestMove);
// Check if the user time has expired
ElapsedTime = DateTime.Now - ThinkStartTime;
if (ElapsedTime.Ticks > (m_MaxThinkTime.Ticks)) // More than 75 percent time is available
{
break; // Force break the loop
}
}
// Check if the user time has expired
ElapsedTime = DateTime.Now - ThinkStartTime;
if (ElapsedTime.Ticks > (m_MaxThinkTime.Ticks * 0.25)) // More than 75 percent time is available
{
break; // Force break the loop
}
}
m_Rules.ChessGame.NotifyComputerThinking(depth, MoveCounter, TotalMoves.Count, m_TotalMovesAnalyzed, BestMove);
return(BestMove);
}
