int OrderMove(Move m, TranspositionTableEntry entry)
{
if (entry != null)
{
if (m.Value == entry.MoveValue)
{
return(int.MaxValue);// search this move first
}
}
if ((m.Bits & (byte)MoveBits.Capture) > 0)
{
//winning and even captures
if (Evaluator.PieceValueOnSquare(MyBoard, m.To) >= Evaluator.PieceValues[(int)Move.GetPiece((MoveBits)m.Bits)])
{
return(LvaMvv(m));
}
else
{
//verify that it is actually losing with SEE
if (StaticExchange.Eval(MyBoard, m, MyBoard.SideToMove) >= 0)
{
return(LvaMvv(m));
}
return(int.MinValue + LvaMvv(m));//losing captures at the bottom
}
}
else
{
//these happen before losing captures
if (Killers[Ply, 0] != null && Killers[Ply, 0].Value == m.Value)
{
return(2);
}
else if (Killers[Ply, 1] != null && Killers[Ply, 1].Value == m.Value)
{
return(1);
}
}
return(0);
}
public int Quiesce(int alpha, int beta)
{
Metrics.Nodes++;
Metrics.QNodes++;
if (Ply >= MAX_DEPTH)
{
TakeBack();
return(Evaluator.Evaluate(MyBoard, -10000, 10000));
}
if ((Metrics.Nodes & 65535) == 65535)
{
Interrupt();
if (MyGameState.TimeUp)
{
return(alpha);
}
}
int score = Evaluator.Evaluate(MyBoard, alpha, beta);
if (score > alpha)
{
alpha = score;
}
//attemp to stand pat (don't search if eval tells us we are in a good position)
var inCheck = MyBoard.InCheck(MyBoard.SideToMove);
if (!inCheck)
{
if (score >= beta)
{
return(beta);
}
//Don't bother searching if we are evaluating at less than a Queen
if (score < alpha - Evaluator.PieceValues[(int)Piece.Queen])
{
return(alpha);
}
}
var moves = MoveGenerator
.GenerateCapturesAndPromotions(MyBoard, false)
.OrderByDescending((m) => OrderQuiesceMove(m));
foreach (var m in moves)
{
if ((BitMask.Mask[m.To] & (MyBoard.King[0] | MyBoard.King[1])) > 0)
{
return(beta);
}
//if SEE says this is a losing capture, we prune it
if (StaticExchange.Eval(MyBoard, m, MyBoard.SideToMove) < 0)
{
continue;
}
MyBoard.MakeMove(m, false);
Ply++;
score = -Quiesce(-beta, -alpha);
TakeBack();
if (score >= beta)
{
return(beta);
}
if (score > alpha)
{
alpha = score;
}
}
return(alpha);
}