public void SearchPosition(BoardState bs, SearchInfo sInfo)
{
var move = "";
var depth = 1;
var bestScore = -Definitions.INFINITE;
while (!sInfo.IsTimeUp() || bestScore < Definitions.MATE - 10)
{
bestScore = AlphaBeta(-Definitions.INFINITE, Definitions.INFINITE, depth, bs, sInfo);
if (bestScore == Definitions.Stopped)
{
bs.BestPly = bs.BestPlyAtLowerDepth;
break;
}
if (bestScore > Definitions.MATE - 20)
{
Console.WriteLine("info depth {1} nodes {2} time {3} score mate {0}", Definitions.MATE - (bestScore / 2 + 1),
depth, sInfo.Nodes, sInfo.ElapsedTime());
break;
}
if (bestScore < -Definitions.MATE + 20)
{
Console.WriteLine("info depth {1} nodes {2} time {3} score mate -{0}", Definitions.MATE - (bestScore / 2 + 1),
depth, sInfo.Nodes, sInfo.ElapsedTime());
}
else
{
Console.WriteLine("info depth {1} nodes {2} time {3} score cp {0}", bestScore, depth, sInfo.Nodes,
sInfo.ElapsedTime());
}
bs.BestPlyAtLowerDepth = bs.BestPly;
/*Console.WriteLine("Move: {3}, Score: {0}, Depth: {1}, Nodes: {4}, Time: {2} ms, Ordering: {5}/{6}.",
* bestScore, depth, sInfo.ElapsedTime(), bs.BestPly.GetAlgebraicPly(),
* sInfo.Nodes, sInfo.Fhf, sInfo.Fh);*/
move = Definitions.IndexToAlgebraic[bs.BestPly.GetFromToSquare()[0]] +
Definitions.IndexToAlgebraic[bs.BestPly.GetFromToSquare()[1]];
Console.WriteLine("info currmove {0}{1}", move, bs.BestPly.Promotion);
depth++;
bs.HaveSearched = false;
}
Console.WriteLine("bestmove {0}{1}", move, bs.BestPly.Promotion);
}
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);
}
// Inspiration from VICE Chess Engine.
public int AlphaBeta(int alpha, int beta, int depth, BoardState bs, SearchInfo sInfo)
{
if (depth == 0)
{
//return _eval.EvalPosition(bs);
return(Quiescene(alpha, beta, bs, sInfo));
}
// Check if time is up or interrupted by the GUI.
if (sInfo.IsTimeUp())
{
sInfo.Stopped = true;
}
sInfo.Nodes++;
/*if (bs.BestPly != null)
* {
* if (bs.FiftyMoveRule >= 100 || _helper.IsRepetition(bs))
* {
* return 0;
* //Console.WriteLine("bestmove: {0}{1}, score {2}", Definitions.IndexToAlgebraic[bs.BestPly.GetFromToSquare()[0]], Definitions.IndexToAlgebraic[bs.BestPly.GetFromToSquare()[1]], bs.BestPly.Score);
* }
* }*/
var mg = new MoveGenerator(bs);
var legalMoves = mg.AllLegalMoves();
Ply bestMove = null;
var nMoves = legalMoves.Length;
var oldAlpha = alpha;
var moveNum = 0;
if (bs.BestPlyAtLowerDepth != null && !bs.HaveSearched)
{
mg.MakeMove(bs.BestPlyAtLowerDepth);
bs.BestPlyAtLowerDepth.Score = -AlphaBeta(-beta, -alpha, depth - 1, bs, sInfo);
mg.UndoMove(bs.BestPlyAtLowerDepth);
bs.HaveSearched = true;
bestMove = bs.BestPlyAtLowerDepth;
alpha = bestMove.Score;
}
for (moveNum = 0; moveNum < legalMoves.Length; moveNum++)
{
mg.MakeMove(legalMoves[moveNum]);
legalMoves[moveNum].Score = -AlphaBeta(-beta, -alpha, depth - 1, bs, sInfo);
mg.UndoMove(legalMoves[moveNum]);
if (sInfo.Stopped)
{
return(Definitions.Stopped);
}
if (legalMoves[moveNum].Score >= beta)
{
if (nMoves == 1)
{
sInfo.Fhf++;
}
sInfo.Fh++;
return(beta); // Fail hard beta-cutoff.
}
if (legalMoves[moveNum].Score > alpha)
{
alpha = legalMoves[moveNum].Score; // alpha acts like max in minimax.
bestMove = legalMoves[moveNum];
}
}
if (nMoves == 0)
{
if (_helper.IsKingInCheck(bs.SideToMove, bs.BoardRepresentation, bs.KingSquares))
{
return(-Definitions.MATE + bs.Ply);
}
// Stalemate.
return(0);
}
if (alpha != oldAlpha)
{
bs.BestPly = bestMove;
}
return(alpha);
}
