// a depth limited quiescence to prevent this from going on and on...
private static int Quiescence_Limited(Board board, sbyte side, int alpha, int beta, int depthLeft)
{
int standingPat = Evaluation2.EvaluateFromPerspectiveOf(board, side);
if (depthLeft == 0)
{
return standingPat;
}
if (standingPat >= beta)
{
return beta;
}
if (alpha < standingPat)
{
alpha = standingPat;
}
sbyte oppositeSide = (sbyte)(-1 * side);
int movesCount;
UInt16[] moves = board.GenerateCaptureMoves(out movesCount);
int score;
BoardState state;
for (int i = 0; i < movesCount; i++)
{
state = board.GetBoardState();
if (!board.MakeMove(moves[i]))
{
continue;
}
score = -Quiescence_Limited(board, oppositeSide, -beta, -alpha, depthLeft - 1);
board.RestoreState(state);
if (score >= beta)
{
return beta;
}
if (score > alpha)
{
alpha = score;
}
}
return alpha;
}
private static int Quiescence(Board board, sbyte side, int alpha, int beta)
{
// from: http://chessprogramming.wikispaces.com/Quiescence+Search
int standingPat = Evaluation2.EvaluateFromPerspectiveOf(board, side);
if (standingPat >= beta)
{
return beta;
}
if (alpha < standingPat)
{
alpha = standingPat;
}
sbyte oppositeSide = (sbyte)(-1 * side);
int movesCount;
UInt16[] moves = board.GenerateCaptureMoves(out movesCount);
int score;
BoardState state;
for (int i = 0; i < movesCount; i++)
{
state = board.GetBoardState();
if (!board.MakeMove(moves[i]))
{
continue;
}
score = -Quiescence(board, oppositeSide, -beta, -alpha);
board.RestoreState(state);
if (score >= beta)
{
return beta;
}
if (score > alpha)
{
alpha = score;
}
}
return alpha;
}