private static int Quiescence(Board examineBoard, int alpha, int beta, ref int nodesSearched) { nodesSearched = nodesSearched + 1; Evaluation.EvaluateBoardScore(examineBoard); examineBoard.Score = Search.SideToMoveScore(examineBoard.Score, examineBoard.WhoseMove); if (examineBoard.Score >= beta) { return(beta); } if (examineBoard.Score > alpha) { alpha = examineBoard.Score; } List <Search.Position> positionList = examineBoard.WhiteCheck || examineBoard.BlackCheck ? Search.EvaluateMoves(examineBoard, (byte)0) : Search.EvaluateMovesQ(examineBoard); if (positionList.Count == 0) { return(examineBoard.Score); } positionList.Sort(new Comparison <Search.Position>(Search.Sort)); foreach (Search.Position position in positionList) { if (Search.StaticExchangeEvaluation(examineBoard.Squares[(int)position.DstPosition]) < 0) { 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 num = -Search.Quiescence(board, -beta, -alpha, ref nodesSearched); if (num >= beta) { Search.KillerMove[2, 0].SrcPosition = position.SrcPosition; Search.KillerMove[2, 0].DstPosition = position.DstPosition; return(beta); } if (num > alpha) { alpha = num; } } } } return(alpha); }
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); }