private void Position(string command)
{
if (command.Contains("startpos"))
{
command = command.Replace("startpos", "fen " + Definitions.STDSETUP);
}
var fen = command;
int index;
string[] moves = null;
if (command.Contains("moves"))
{
index = command.IndexOf("moves") - 1;
fen = command.Substring(0, index);
index = command.IndexOf("moves") + 6;
var temp = command.Substring(index);
moves = temp.Split(' ');
}
index = fen.IndexOf("fen") + 4;
fen = fen.Substring(index);
//Console.WriteLine(fen);
// Setup new BoardState.
_bs = _helper.BoardsetupFromFen(fen);
/*_bs.PieceKeys = _zobrist.InitZobrist(_bs);
* _bs.PosKey = _zobrist.Hash(_bs);*/
if (moves == null)
{
return;
}
var mg = new MoveGenerator(_bs);
foreach (var move in moves)
{
// perform those moves
var validMoves = mg.AllLegalMoves();
foreach (var validMove in validMoves)
{
var algebraic = Definitions.IndexToAlgebraic[validMove.GetFromToSquare()[0]] +
Definitions.IndexToAlgebraic[validMove.GetFromToSquare()[1]] + validMove.Promotion;
if (algebraic == move)
{
mg.MakeMove(validMove);
break;
}
}
}
//_helper.PrintBoardWhitePerspective(_bs.BoardRepresentation);
}
// 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);
}