public int Quiescene(int alpha, int beta, BoardState bs, SearchInfo sInfo)
{
if (sInfo.IsTimeUp())
{
sInfo.Stopped = true;
}
//sInfo.Nodes++;
/*if (_helper.IsRepetition(bs) || bs.FiftyMoveRule >= 100)
* {
* //if (bs.BestPly != null) bs.BestPly.Score = 0;
* return 0;
* }*/
var score = _eval.EvalPosition(bs);
if (score >= beta)
{
return(beta);
}
if (score > alpha)
{
alpha = score;
}
var mg = new MoveGenerator(bs);
var capMoves = mg.AllCapMoves();
Ply bestMove = null;
var nMoves = 0;
if (capMoves != null)
{
nMoves = capMoves.Length;
}
var oldAlpha = alpha;
var moveNum = 0;
if (bs.BestPlyAtLowerDepth != null && !bs.HaveSearched)
{
mg.MakeMove(bs.BestPlyAtLowerDepth);
bs.BestPlyAtLowerDepth.Score = -Quiescene(-beta, -alpha, bs, sInfo);
mg.UndoMove(bs.BestPlyAtLowerDepth);
bs.HaveSearched = true;
bestMove = bs.BestPlyAtLowerDepth;
alpha = bestMove.Score;
//Console.WriteLine("This never happens.");
}
for (moveNum = 0; moveNum < nMoves; moveNum++)
{
mg.MakeMove(capMoves[moveNum]);
capMoves[moveNum].Score = -Quiescene(-beta, -alpha, bs, sInfo);
mg.UndoMove(capMoves[moveNum]);
if (sInfo.Stopped)
{
return(Definitions.Stopped);
}
if (capMoves[moveNum].Score <= alpha)
{
continue;
}
if (capMoves[moveNum].Score >= beta)
{
if (nMoves == 1)
{
sInfo.Fhf++;
}
sInfo.Fh++;
return(beta); // Fail hard beta-cutoff.
}
alpha = capMoves[moveNum].Score; // alpha acts like max in minimax.
bestMove = capMoves[moveNum];
}
if (alpha != oldAlpha)
{
//Console.WriteLine("New best ply!");
bs.BestPly = bestMove;
}
return(alpha);
}