private static bool CheckForMate(ChessPieceColor whosTurn, ref Board chessBoard)
{
Search.SearchForMate(whosTurn, chessBoard, ref chessBoard.BlackMate,
ref chessBoard.WhiteMate, ref chessBoard.StaleMate);
if (chessBoard.BlackMate || chessBoard.WhiteMate || chessBoard.StaleMate)
{
return(true);
}
return(false);
}
private static int AlphaBeta(Board examineBoard, byte depth, int alpha, int beta, ref int nodesSearched, ref int nodesQuiessence, ref List <Search.Position> pvLine, bool extended)
{
nodesSearched = nodesSearched + 1;
if ((int)examineBoard.FiftyMove >= 50 || (int)examineBoard.RepeatedMove >= 3)
{
return(0);
}
int?nullable1 = Zobrist.Search(examineBoard.ZobristHash, depth, alpha, beta);
if (nullable1.HasValue)
{
return(nullable1.Value);
}
if ((int)depth == 0)
{
if (!extended && examineBoard.BlackCheck || examineBoard.WhiteCheck)
{
++depth;
extended = true;
}
else
{
int score = Search.Quiescence(examineBoard, alpha, beta, ref nodesQuiessence);
if (score >= beta)
{
Zobrist.AddEntry(examineBoard.ZobristHash, depth, score, Zobrist.NodeType.Beta);
}
else if (score <= alpha)
{
Zobrist.AddEntry(examineBoard.ZobristHash, depth, score, Zobrist.NodeType.Alpha);
}
else
{
Zobrist.AddEntry(examineBoard.ZobristHash, depth, score, Zobrist.NodeType.Exact);
}
return(score);
}
}
Zobrist.NodeType nodeType = Zobrist.NodeType.Alpha;
List <Search.Position> moves = Search.EvaluateMoves(examineBoard, depth);
if ((examineBoard.WhiteCheck || examineBoard.BlackCheck || moves.Count == 0) && Search.SearchForMate(examineBoard.WhoseMove, examineBoard, ref examineBoard.BlackMate, ref examineBoard.WhiteMate, ref examineBoard.StaleMate))
{
if (examineBoard.BlackMate)
{
if (examineBoard.WhoseMove == ChessPieceColor.Black)
{
return(-32767 - (int)depth);
}
return((int)short.MaxValue + (int)depth);
}
if (!examineBoard.WhiteMate)
{
return(0);
}
if (examineBoard.WhoseMove == ChessPieceColor.Black)
{
return((int)short.MaxValue + (int)depth);
}
return(-32767 - (int)depth);
}
moves.Sort(new Comparison <Search.Position>(Search.Sort));
foreach (Search.Position position in moves)
{
List <Search.Position> pvLine1 = new List <Search.Position>();
Board board = examineBoard.FastCopy();
Board.MovePiece(board, position.SrcPosition, position.DstPosition, ChessPieceType.Queen);
PieceValidMoves.GenerateValidMoves(board);
if ((!board.BlackCheck || examineBoard.WhoseMove != ChessPieceColor.Black) && (!board.WhiteCheck || examineBoard.WhoseMove != ChessPieceColor.White))
{
int?nullable2 = new int?(-Search.AlphaBeta(board, (byte)((uint)depth - 1U), -beta, -alpha, ref nodesSearched, ref nodesQuiessence, ref pvLine1, extended));
int?nullable3 = nullable2;
int num1 = beta;
if ((nullable3.GetValueOrDefault() >= num1 ? (nullable3.HasValue ? 1 : 0) : 0) != 0)
{
Search.KillerMove[Search.kIndex, (int)depth].SrcPosition = position.SrcPosition;
Search.KillerMove[Search.kIndex, (int)depth].DstPosition = position.DstPosition;
Search.kIndex = (Search.kIndex + 1) % 2;
Zobrist.AddEntry(examineBoard.ZobristHash, depth, nullable2.Value, Zobrist.NodeType.Beta);
return(beta);
}
nullable3 = nullable2;
int num2 = alpha;
if ((nullable3.GetValueOrDefault() > num2 ? (nullable3.HasValue ? 1 : 0) : 0) != 0)
{
pvLine1.Insert(0, new Search.Position()
{
SrcPosition = board.LastMove.MovingPiecePrimary.SrcPosition,
DstPosition = board.LastMove.MovingPiecePrimary.DstPosition,
Move = board.LastMove.ToString()
});
pvLine = pvLine1;
alpha = nullable2.Value;
nodeType = Zobrist.NodeType.Exact;
}
}
}
Zobrist.AddEntry(examineBoard.ZobristHash, depth, alpha, nodeType);
return(alpha);
}