int AlphaBeta(int depth, int alpha, int beta)
{
int score = 0;
int ttMove = 0;
int bestMove = 0;
TTType ttFlag = TTType.Alpha;
if (clk.GetElapsedMilliseconds() > totalMillisec)
{
return(0); // timeout
}
if (depth == 0)
{
return(Quiesce(alpha, beta, 0));
}
else
{
if (ttable.Probe(board.ZKey, depth, alpha, beta, ref ttMove, ref score))
{
return(score);
}
bestMove = ttMove;
var moves = GetMoves(bestMove, depth);
if (moves.Count() == 0)
{
score = board.InCheck(board.ToMove)?-INFINITE:0;
ttable.Save(board.ZKey, depth, score, TTType.Exact, 0);
return(score);
}
foreach (var move in moves)
{
board.Move(move);
score = -AlphaBeta(depth - 1, -beta, -alpha);
board.UndoMove();
if (score > alpha)
{
bestMove = move;
alpha = score;
ttFlag = TTType.Exact;
}
if (alpha >= beta) // current plaier move is better than the other one better, no reason to search further
{
//beta cutoff !!!
ttable.Save(board.ZKey, depth, beta, TTType.Beta, bestMove);
if (0 != (MovePackHelper.Capture & move))
{
StoreKiller(depth, move);
}
return(beta);
}
}
ttable.Save(board.ZKey, depth, alpha, ttFlag, bestMove);
return(alpha);
}
}