/// KQ vs KR. This is almost identical to KX vs K: We give the attacking /// king a bonus for having the kings close together, and for forcing the /// defending king towards the edge. If we also take care to avoid null move /// for the defending side in the search, this is usually sufficient to be /// able to win KQ vs KR. internal static Value Endgame_KQKR(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.QueenValueMidgame); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 0); Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.RookValueMidgame); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0); Square winnerKSq = pos.king_square(strongerSide); Square loserKSq = pos.king_square(weakerSide); Value result = Constants.QueenValueEndgame - Constants.RookValueEndgame + MateTable[loserKSq] + DistanceBonus[Utils.square_distance(winnerKSq, loserKSq)]; return strongerSide == pos.sideToMove ? result : -result; }
/// K and queen vs K, rook and one or more pawns. It tests for fortress draws with /// a rook on the third rank defended by a pawn. internal static ScaleFactor Endgame_KQKRPs(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.QueenValueMidgame); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.QUEEN) == 1); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 0); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.ROOK) == 1); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) >= 1); Square kingSq = pos.king_square(weakerSide); if (Utils.relative_rank_CS(weakerSide, kingSq) <= RankC.RANK_2 && Utils.relative_rank_CS(weakerSide, pos.king_square(strongerSide)) >= RankC.RANK_4 && ((pos.pieces_PTC(PieceTypeC.ROOK, weakerSide) & Utils.rank_bb_R(Utils.relative_rank_CR(weakerSide, RankC.RANK_3))) != 0) && ((pos.pieces_PTC(PieceTypeC.PAWN, weakerSide) & Utils.rank_bb_R(Utils.relative_rank_CR(weakerSide, RankC.RANK_2))) != 0) && ((Position.attacks_from_KING(kingSq) & pos.pieces_PTC(PieceTypeC.PAWN, weakerSide)) != 0) ) { Square rsq = pos.pieceList[weakerSide][PieceTypeC.ROOK][0]; if ((Position.attacks_from_PAWN(rsq, strongerSide) & pos.pieces_PTC(PieceTypeC.PAWN, weakerSide)) != 0) return ScaleFactorC.SCALE_FACTOR_DRAW; } return ScaleFactorC.SCALE_FACTOR_NONE; }
internal static bool is_KQKRPs(int Us, Position pos) { var Them = (Us == ColorC.WHITE ? ColorC.BLACK : ColorC.WHITE); return pos.piece_count(Us, PieceTypeC.PAWN) == 0 && pos.non_pawn_material(Us) == Constants.QueenValueMidgame && pos.piece_count(Us, PieceTypeC.QUEEN) == 1 && pos.piece_count(Them, PieceTypeC.ROOK) == 1 && pos.piece_count(Them, PieceTypeC.PAWN) >= 1; }
/// KQ vs KP. In general, a win for the stronger side, however, there are a few /// important exceptions. Pawn on 7th rank, A,C,F or H file, with king next can /// be a draw, so we scale down to distance between kings only. internal static int Endgame_KQKP(int strongerSide, Position pos) { var weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.QueenValueMidgame); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 0); Debug.Assert(pos.non_pawn_material(weakerSide) == 0); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 1); Square winnerKSq = pos.king_square(strongerSide); Square loserKSq = pos.king_square(weakerSide); Square pawnSq = pos.pieceList[weakerSide][PieceTypeC.PAWN][0]; var result = Constants.QueenValueEndgame - Constants.PawnValueEndgame + DistanceBonus[Utils.square_distance(winnerKSq, loserKSq)]; if ( Utils.square_distance(loserKSq, pawnSq) == 1 && Utils.relative_rank_CS(weakerSide, pawnSq) == RankC.RANK_7) { File f = Utils.file_of(pawnSq); if (f == FileC.FILE_A || f == FileC.FILE_C || f == FileC.FILE_F || f == FileC.FILE_H) { result = DistanceBonus[Utils.square_distance(winnerKSq, loserKSq)]; } } return strongerSide == pos.sideToMove ? result : -result; }
/// K, rook and two pawns vs K, rook and one pawn. There is only a single /// pattern: If the stronger side has no passed pawns and the defending king /// is actively placed, the position is drawish. internal static ScaleFactor Endgame_KRPPKRP(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.RookValueMidgame); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 2); Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.RookValueMidgame); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 1); Square wpsq1 = pos.pieceList[strongerSide][PieceTypeC.PAWN][0]; Square wpsq2 = pos.pieceList[strongerSide][PieceTypeC.PAWN][1]; Square bksq = pos.king_square(weakerSide); // Does the stronger side have a passed pawn? if (pos.pawn_is_passed(strongerSide, wpsq1) || pos.pawn_is_passed(strongerSide, wpsq2)) return ScaleFactorC.SCALE_FACTOR_NONE; Rank r = Math.Max(Utils.relative_rank_CS(strongerSide, wpsq1), Utils.relative_rank_CS(strongerSide, wpsq2)); if (Utils.file_distance(bksq, wpsq1) <= 1 && Utils.file_distance(bksq, wpsq2) <= 1 && Utils.relative_rank_CS(strongerSide, bksq) > r) { switch (r) { case RankC.RANK_2: return (10); case RankC.RANK_3: return (10); case RankC.RANK_4: return (15); case RankC.RANK_5: return (20); case RankC.RANK_6: return (40); default: Debug.Assert(false); break; } } return ScaleFactorC.SCALE_FACTOR_NONE; }
internal static bool is_KXK(int Us, Position pos) { var Them = (Us == ColorC.WHITE ? ColorC.BLACK : ColorC.WHITE); return pos.non_pawn_material(Them) == ValueC.VALUE_ZERO && pos.piece_count(Them, PieceTypeC.PAWN) == 0 && pos.non_pawn_material(Us) >= Constants.RookValueMidgame; }
/// K, bishop and two pawns vs K and bishop. It detects a few basic draws with /// opposite-colored bishops. internal static ScaleFactor Endgame_KBPPKB(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.BishopValueMidgame); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.BISHOP) == 1); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 2); Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.BishopValueMidgame); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.BISHOP) == 1); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0); Square wbsq = pos.pieceList[strongerSide][PieceTypeC.BISHOP][0]; Square bbsq = pos.pieceList[weakerSide][PieceTypeC.BISHOP][0]; if (!Utils.opposite_colors(wbsq, bbsq)) return ScaleFactorC.SCALE_FACTOR_NONE; Square ksq = pos.king_square(weakerSide); Square psq1 = pos.pieceList[strongerSide][PieceTypeC.PAWN][0]; Square psq2 = pos.pieceList[strongerSide][PieceTypeC.PAWN][1]; Rank r1 = Utils.rank_of(psq1); Rank r2 = Utils.rank_of(psq2); Square blockSq1, blockSq2; if (Utils.relative_rank_CS(strongerSide, psq1) > Utils.relative_rank_CS(strongerSide, psq2)) { blockSq1 = psq1 + Utils.pawn_push(strongerSide); blockSq2 = Utils.make_square(Utils.file_of(psq2), Utils.rank_of(psq1)); } else { blockSq1 = psq2 + Utils.pawn_push(strongerSide); blockSq2 = Utils.make_square(Utils.file_of(psq1), Utils.rank_of(psq2)); } switch (Utils.file_distance(psq1, psq2)) { case 0: // Both pawns are on the same file. Easy draw if defender firmly controls // some square in the frontmost pawn's path. if (Utils.file_of(ksq) == Utils.file_of(blockSq1) && Utils.relative_rank_CS(strongerSide, ksq) >= Utils.relative_rank_CS(strongerSide, blockSq1) && Utils.opposite_colors(ksq, wbsq)) return ScaleFactorC.SCALE_FACTOR_DRAW; else return ScaleFactorC.SCALE_FACTOR_NONE; case 1: // Pawns on adjacent files. Draw if defender firmly controls the square // in front of the frontmost pawn's path, and the square diagonally behind // this square on the file of the other pawn. if (ksq == blockSq1 && Utils.opposite_colors(ksq, wbsq) && (bbsq == blockSq2 || (((pos.attacks_from_BISHOP(blockSq2) & pos.pieces_PTC(PieceTypeC.BISHOP, weakerSide))) != 0) || Math.Abs(r1 - r2) >= 2)) return ScaleFactorC.SCALE_FACTOR_DRAW; else if (ksq == blockSq2 && Utils.opposite_colors(ksq, wbsq) && (bbsq == blockSq1 || (((pos.attacks_from_BISHOP(blockSq1) & pos.pieces_PTC(PieceTypeC.BISHOP, weakerSide)))) != 0)) return ScaleFactorC.SCALE_FACTOR_DRAW; else return ScaleFactorC.SCALE_FACTOR_NONE; default: // The pawns are not on the same file or adjacent files. No scaling. return ScaleFactorC.SCALE_FACTOR_NONE; } }
/// KR vs KP. This is a somewhat tricky endgame to evaluate precisely without /// a bitbase. The function below returns drawish scores when the pawn is /// far advanced with support of the king, while the attacking king is far /// away. internal static Value Endgame_KRKP(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.RookValueMidgame); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 0); Debug.Assert(pos.non_pawn_material(weakerSide) == 0); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 1); Square wksq, wrsq, bksq, bpsq; int tempo = (pos.sideToMove == strongerSide ? 1 : 0); wksq = pos.king_square(strongerSide); wrsq = pos.pieceList[strongerSide][PieceTypeC.ROOK][0]; bksq = pos.king_square(weakerSide); bpsq = pos.pieceList[weakerSide][PieceTypeC.PAWN][0]; if (strongerSide == ColorC.BLACK) { wksq = Utils.flip_S(wksq); wrsq = Utils.flip_S(wrsq); bksq = Utils.flip_S(bksq); bpsq = Utils.flip_S(bpsq); } Square queeningSq = Utils.make_square(Utils.file_of(bpsq), RankC.RANK_1); Value result; // If the stronger side's king is in front of the pawn, it's a win if (wksq < bpsq && Utils.file_of(wksq) == Utils.file_of(bpsq)) result = Constants.RookValueEndgame - (Utils.square_distance(wksq, bpsq)); // If the weaker side's king is too far from the pawn and the rook, // it's a win else if (Utils.square_distance(bksq, bpsq) - (tempo ^ 1) >= 3 && Utils.square_distance(bksq, wrsq) >= 3) result = Constants.RookValueEndgame - (Utils.square_distance(wksq, bpsq)); // If the pawn is far advanced and supported by the defending king, // the position is drawish else if (Utils.rank_of(bksq) <= RankC.RANK_3 && Utils.square_distance(bksq, bpsq) == 1 && Utils.rank_of(wksq) >= RankC.RANK_4 && Utils.square_distance(wksq, bpsq) - tempo > 2) result = (80 - Utils.square_distance(wksq, bpsq) * 8); else result = (200) - (Utils.square_distance(wksq, bpsq + SquareC.DELTA_S) * 8) + (Utils.square_distance(bksq, bpsq + SquareC.DELTA_S) * 8) + (Utils.square_distance(bpsq, queeningSq) * 8); return strongerSide == pos.sideToMove ? result : -result; }
/// K, bishop and a pawn vs K and a bishop. There are two rules: If the defending /// king is somewhere along the path of the pawn, and the square of the king is /// not of the same color as the stronger side's bishop, it's a draw. If the two /// bishops have opposite color, it's almost always a draw. internal static ScaleFactor Endgame_KBPKB(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.BishopValueMidgame); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.BISHOP) == 1); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 1); Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.BishopValueMidgame); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.BISHOP) == 1); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0); Square pawnSq = pos.pieceList[strongerSide][PieceTypeC.PAWN][0]; Square strongerBishopSq = pos.pieceList[strongerSide][PieceTypeC.BISHOP][0]; Square weakerBishopSq = pos.pieceList[weakerSide][PieceTypeC.BISHOP][0]; Square weakerKingSq = pos.king_square(weakerSide); // Case 1: Defending king blocks the pawn, and cannot be driven away if (Utils.file_of(weakerKingSq) == Utils.file_of(pawnSq) && Utils.relative_rank_CS(strongerSide, pawnSq) < Utils.relative_rank_CS(strongerSide, weakerKingSq) && (Utils.opposite_colors(weakerKingSq, strongerBishopSq) || Utils.relative_rank_CS(strongerSide, weakerKingSq) <= RankC.RANK_6)) return ScaleFactorC.SCALE_FACTOR_DRAW; // Case 2: Opposite colored bishops if (Utils.opposite_colors(strongerBishopSq, weakerBishopSq)) { // We assume that the position is drawn in the following three situations: // // a. The pawn is on rank 5 or further back. // b. The defending king is somewhere in the pawn's path. // c. The defending bishop attacks some square along the pawn's path, // and is at least three squares away from the pawn. // // These rules are probably not perfect, but in practice they work // reasonably well. if (Utils.relative_rank_CS(strongerSide, pawnSq) <= RankC.RANK_5) return ScaleFactorC.SCALE_FACTOR_DRAW; else { Bitboard path = Utils.forward_bb(strongerSide, pawnSq); if ((path & pos.pieces_PTC(PieceTypeC.KING, weakerSide)) != 0) return ScaleFactorC.SCALE_FACTOR_DRAW; if (((pos.attacks_from_BISHOP(weakerBishopSq) & path) != 0) && Utils.square_distance(weakerBishopSq, pawnSq) >= 3) return ScaleFactorC.SCALE_FACTOR_DRAW; } } return ScaleFactorC.SCALE_FACTOR_NONE; }
/// K, bishop and a pawn vs K and knight. There is a single rule: If the defending /// king is somewhere along the path of the pawn, and the square of the king is /// not of the same color as the stronger side's bishop, it's a draw. internal static ScaleFactor Endgame_KBPKN(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.BishopValueMidgame); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.BISHOP) == 1); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 1); Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.KnightValueMidgame); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.KNIGHT) == 1); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0); Square pawnSq = pos.pieceList[strongerSide][PieceTypeC.PAWN][0]; Square strongerBishopSq = pos.pieceList[strongerSide][PieceTypeC.BISHOP][0]; Square weakerKingSq = pos.king_square(weakerSide); if (Utils.file_of(weakerKingSq) == Utils.file_of(pawnSq) && Utils.relative_rank_CS(strongerSide, pawnSq) < Utils.relative_rank_CS(strongerSide, weakerKingSq) && (Utils.opposite_colors(weakerKingSq, strongerBishopSq) || Utils.relative_rank_CS(strongerSide, weakerKingSq) <= RankC.RANK_6)) return ScaleFactorC.SCALE_FACTOR_DRAW; return ScaleFactorC.SCALE_FACTOR_NONE; }
/// Mate with KBN vs K. This is similar to KX vs K, but we have to drive the /// defending king towards a corner square of the right color. internal static Value Endgame_KBNK(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(weakerSide) == ValueC.VALUE_ZERO); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == ValueC.VALUE_ZERO); Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.KnightValueMidgame + Constants.BishopValueMidgame); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.BISHOP) == 1); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.KNIGHT) == 1); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 0); Square winnerKSq = pos.king_square(strongerSide); Square loserKSq = pos.king_square(weakerSide); Square bishopSquare = pos.pieceList[strongerSide][PieceTypeC.BISHOP][0]; // kbnk_mate_table() tries to drive toward corners A1 or H8, // if we have a bishop that cannot reach the above squares we // mirror the kings so to drive enemy toward corners A8 or H1. if (Utils.opposite_colors(bishopSquare, SquareC.SQ_A1)) { winnerKSq = Utils.mirror(winnerKSq); loserKSq = Utils.mirror(loserKSq); } Value result = ValueC.VALUE_KNOWN_WIN + DistanceBonus[Utils.square_distance(winnerKSq, loserKSq)] + KBNKMateTable[loserKSq]; return strongerSide == pos.sideToMove ? result : -result; }
internal static Value Endgame_KBBKN(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.BISHOP) == 2); Debug.Assert(pos.non_pawn_material(strongerSide) == 2 * Constants.BishopValueMidgame); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.KNIGHT) == 1); Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.KnightValueMidgame); Debug.Assert(pos.pieces_PT(PieceTypeC.PAWN) == 0); Value result = Constants.BishopValueEndgame; Square wksq = pos.king_square(strongerSide); Square bksq = pos.king_square(weakerSide); Square nsq = pos.pieceList[weakerSide][PieceTypeC.KNIGHT][0]; // Bonus for attacking king close to defending king result += (DistanceBonus[Utils.square_distance(wksq, bksq)]); // Bonus for driving the defending king and knight apart result += (Utils.square_distance(bksq, nsq) * 32); // Bonus for restricting the knight's mobility result += ((8 - Bitcount.popcount_1s_Max15(Position.attacks_from_KNIGHT(nsq))) * 8); return strongerSide == pos.sideToMove ? result : -result; }
internal int update_safety_BLACK(Position pos, int ksq) { this.kingSquaresBLACK = ksq; this.castleRightsBLACK = pos.st.castleRights & CastleRightC.BLACK_ANY; ulong pawns = (ulong)pos.piece_count(ColorC.BLACK, PieceTypeC.PAWN); if (pawns > 0) { var minDist = this.minKPdistanceBLACK; while ((Utils.DistanceRingsBB[ksq][minDist++] & pawns) != pawns) { } } if (((ksq >> 3) ^ (ColorC.BLACK * 7)) > RankC.RANK_4) { return this.kingSafetyBLACK = Utils.make_score(0, -16 * this.minKPdistanceBLACK); } var bonus = shelter_storm(ColorC.BLACK, pos, ksq); // If we can castle use the bonus after the castle if is bigger if ((pos.st.castleRights & CastleRightC.BLACK_OO) != 0) { bonus = Math.Max(bonus, shelter_storm(ColorC.BLACK, pos, (SquareC.SQ_G1 ^ (ColorC.BLACK * 56)))); } if ((pos.st.castleRights & CastleRightC.BLACK_OOO) != 0) { bonus = Math.Max(bonus, shelter_storm(ColorC.BLACK, pos, (SquareC.SQ_C1 ^ (ColorC.BLACK * 56)))); } return this.kingSafetyBLACK = Utils.make_score(bonus, -16 * this.minKPdistanceBLACK); }
/// KR vs KB. This is very simple, and always returns drawish scores. The /// score is slightly bigger when the defending king is close to the edge. internal static Value Endgame_KRKB(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.RookValueMidgame); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 0); Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.BishopValueMidgame); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.BISHOP) == 1); Value result = (MateTable[pos.king_square(weakerSide)]); return strongerSide == pos.sideToMove ? result : -result; }
/// K, bishop and one or more pawns vs K. It checks for draws with rook pawns and /// a bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_DRAW /// is returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling /// will be used. internal static ScaleFactor Endgame_KBPsK(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.BishopValueMidgame); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.BISHOP) == 1); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) >= 1); // No Debug.Assertions about the material of weakerSide, because we want draws to // be detected even when the weaker side has some pawns. Bitboard pawns = pos.pieces_PTC(PieceTypeC.PAWN, strongerSide); File pawnFile = Utils.file_of(pos.pieceList[strongerSide][PieceTypeC.PAWN][0]); // All pawns are on a single rook file ? if ((pawnFile == FileC.FILE_A || pawnFile == FileC.FILE_H) && (((pawns & ~Utils.file_bb_F(pawnFile))) == 0)) { Square bishopSq = pos.pieceList[strongerSide][PieceTypeC.BISHOP][0]; Square queeningSq = Utils.relative_square(strongerSide, Utils.make_square(pawnFile, RankC.RANK_8)); Square kingSq = pos.king_square(weakerSide); if (Utils.opposite_colors(queeningSq, bishopSq) && Math.Abs(Utils.file_of(kingSq) - pawnFile) <= 1) { // The bishop has the wrong color, and the defending king is on the // file of the pawn(s) or the adjacent file. Find the rank of the // frontmost pawn. Rank rank; if (strongerSide == ColorC.WHITE) { for (rank = RankC.RANK_7; (((Utils.rank_bb_R(rank) & pawns)) == 0); rank--) { } Debug.Assert(rank >= RankC.RANK_2 && rank <= RankC.RANK_7); } else { for (rank = RankC.RANK_2; (((Utils.rank_bb_R(rank) & pawns)) == 0); rank++) { } rank = (rank ^ 7); // HACK to get the relative rank Debug.Assert(rank >= RankC.RANK_2 && rank <= RankC.RANK_7); } // If the defending king has distance 1 to the promotion square or // is placed somewhere in front of the pawn, it's a draw. if (Utils.square_distance(kingSq, queeningSq) <= 1 || Utils.relative_rank_CS(strongerSide, kingSq) >= rank) return ScaleFactorC.SCALE_FACTOR_DRAW; } } return ScaleFactorC.SCALE_FACTOR_NONE; }
/// KR vs KN. The attacking side has slightly better winning chances than /// in KR vs KB, particularly if the king and the knight are far apart. internal static Value Endgame_KRKN(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.RookValueMidgame); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 0); Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.KnightValueMidgame); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.KNIGHT) == 1); Square bksq = pos.king_square(weakerSide); Square bnsq = pos.pieceList[weakerSide][PieceTypeC.KNIGHT][0]; Value result = (MateTable[bksq] + penalty[Utils.square_distance(bksq, bnsq)]); return strongerSide == pos.sideToMove ? result : -result; }
/// K, knight and a pawn vs K. There is a single rule: If the pawn is a rook pawn /// on the 7th rank and the defending king prevents the pawn from advancing, the /// position is drawn. internal static ScaleFactor Endgame_KNPK(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.KnightValueMidgame); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.KNIGHT) == 1); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 1); Debug.Assert(pos.non_pawn_material(weakerSide) == ValueC.VALUE_ZERO); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0); Square pawnSq = pos.pieceList[strongerSide][PieceTypeC.PAWN][0]; Square weakerKingSq = pos.king_square(weakerSide); if (pawnSq == Utils.relative_square(strongerSide, SquareC.SQ_A7) && Utils.square_distance(weakerKingSq, Utils.relative_square(strongerSide, SquareC.SQ_A8)) <= 1) return ScaleFactorC.SCALE_FACTOR_DRAW; if (pawnSq == Utils.relative_square(strongerSide, SquareC.SQ_H7) && Utils.square_distance(weakerKingSq, Utils.relative_square(strongerSide, SquareC.SQ_H8)) <= 1) return ScaleFactorC.SCALE_FACTOR_DRAW; return ScaleFactorC.SCALE_FACTOR_NONE; }
/// K, rook and one pawn vs K and a rook. This function knows a handful of the /// most important classes of drawn positions, but is far from perfect. It would /// probably be a good idea to add more knowledge in the future. /// /// It would also be nice to rewrite the actual code for this function, /// which is mostly copied from Glaurung 1.x, and not very pretty. internal static ScaleFactor Endgame_KRPKR(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.RookValueMidgame); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 1); Debug.Assert(pos.non_pawn_material(weakerSide) == Constants.RookValueMidgame); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0); Square wksq = pos.king_square(strongerSide); Square wrsq = pos.pieceList[strongerSide][PieceTypeC.ROOK][0]; Square wpsq = pos.pieceList[strongerSide][PieceTypeC.PAWN][0]; Square bksq = pos.king_square(weakerSide); Square brsq = pos.pieceList[weakerSide][PieceTypeC.ROOK][0]; // Orient the board in such a way that the stronger side is white, and the // pawn is on the left half of the board. if (strongerSide == ColorC.BLACK) { wksq = Utils.flip_S(wksq); wrsq = Utils.flip_S(wrsq); wpsq = Utils.flip_S(wpsq); bksq = Utils.flip_S(bksq); brsq = Utils.flip_S(brsq); } if (Utils.file_of(wpsq) > FileC.FILE_D) { wksq = Utils.mirror(wksq); wrsq = Utils.mirror(wrsq); wpsq = Utils.mirror(wpsq); bksq = Utils.mirror(bksq); brsq = Utils.mirror(brsq); } File f = Utils.file_of(wpsq); Rank r = Utils.rank_of(wpsq); Square queeningSq = Utils.make_square(f, RankC.RANK_8); int tempo = (pos.sideToMove == strongerSide ? 1 : 0); // If the pawn is not too far advanced and the defending king defends the // queening square, use the third-rank defence. if (r <= RankC.RANK_5 && Utils.square_distance(bksq, queeningSq) <= 1 && wksq <= SquareC.SQ_H5 && (Utils.rank_of(brsq) == RankC.RANK_6 || (r <= RankC.RANK_3 && Utils.rank_of(wrsq) != RankC.RANK_6))) return ScaleFactorC.SCALE_FACTOR_DRAW; // The defending side saves a draw by checking from behind in case the pawn // has advanced to the 6th rank with the king behind. if (r == RankC.RANK_6 && Utils.square_distance(bksq, queeningSq) <= 1 && Utils.rank_of(wksq) + tempo <= RankC.RANK_6 && (Utils.rank_of(brsq) == RankC.RANK_1 || ((tempo == 0) && Math.Abs(Utils.file_of(brsq) - f) >= 3))) return ScaleFactorC.SCALE_FACTOR_DRAW; if (r >= RankC.RANK_6 && bksq == queeningSq && Utils.rank_of(brsq) == RankC.RANK_1 && ((tempo == 0) || Utils.square_distance(wksq, wpsq) >= 2)) return ScaleFactorC.SCALE_FACTOR_DRAW; // White pawn on a7 and rook on a8 is a draw if black's king is on g7 or h7 // and the black rook is behind the pawn. if (wpsq == SquareC.SQ_A7 && wrsq == SquareC.SQ_A8 && (bksq == SquareC.SQ_H7 || bksq == SquareC.SQ_G7) && Utils.file_of(brsq) == FileC.FILE_A && (Utils.rank_of(brsq) <= RankC.RANK_3 || Utils.file_of(wksq) >= FileC.FILE_D || Utils.rank_of(wksq) <= RankC.RANK_5)) return ScaleFactorC.SCALE_FACTOR_DRAW; // If the defending king blocks the pawn and the attacking king is too far // away, it's a draw. if (r <= RankC.RANK_5 && bksq == wpsq + SquareC.DELTA_N && Utils.square_distance(wksq, wpsq) - tempo >= 2 && Utils.square_distance(wksq, brsq) - tempo >= 2) return ScaleFactorC.SCALE_FACTOR_DRAW; // Pawn on the 7th rank supported by the rook from behind usually wins if the // attacking king is closer to the queening square than the defending king, // and the defending king cannot gain tempi by threatening the attacking rook. if (r == RankC.RANK_7 && f != FileC.FILE_A && Utils.file_of(wrsq) == f && wrsq != queeningSq && (Utils.square_distance(wksq, queeningSq) < Utils.square_distance(bksq, queeningSq) - 2 + tempo) && (Utils.square_distance(wksq, queeningSq) < Utils.square_distance(bksq, wrsq) + tempo)) return (ScaleFactorC.SCALE_FACTOR_MAX - 2 * Utils.square_distance(wksq, queeningSq)); // Similar to the above, but with the pawn further back if (f != FileC.FILE_A && Utils.file_of(wrsq) == f && wrsq < wpsq && (Utils.square_distance(wksq, queeningSq) < Utils.square_distance(bksq, queeningSq) - 2 + tempo) && (Utils.square_distance(wksq, wpsq + SquareC.DELTA_N) < Utils.square_distance(bksq, wpsq + SquareC.DELTA_N) - 2 + tempo) && (Utils.square_distance(bksq, wrsq) + tempo >= 3 || (Utils.square_distance(wksq, queeningSq) < Utils.square_distance(bksq, wrsq) + tempo && (Utils.square_distance(wksq, wpsq + SquareC.DELTA_N) < Utils.square_distance(bksq, wrsq) + tempo)))) return (ScaleFactorC.SCALE_FACTOR_MAX - 8 * Utils.square_distance(wpsq, queeningSq) - 2 * Utils.square_distance(wksq, queeningSq)); // If the pawn is not far advanced, and the defending king is somewhere in // the pawn's path, it's probably a draw. if (r <= RankC.RANK_4 && bksq > wpsq) { if (Utils.file_of(bksq) == Utils.file_of(wpsq)) return (10); if (Math.Abs(Utils.file_of(bksq) - Utils.file_of(wpsq)) == 1 && Utils.square_distance(wksq, bksq) > 2) return (24 - 2 * Utils.square_distance(wksq, bksq)); } return ScaleFactorC.SCALE_FACTOR_NONE; }
/// KP vs K. This endgame is evaluated with the help of a bitbase. internal static Value Endgame_KPK(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(strongerSide) == ValueC.VALUE_ZERO); Debug.Assert(pos.non_pawn_material(weakerSide) == ValueC.VALUE_ZERO); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) == 1); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0); Square wksq, bksq, wpsq; Color stm; if (strongerSide == ColorC.WHITE) { wksq = pos.king_square(ColorC.WHITE); bksq = pos.king_square(ColorC.BLACK); wpsq = pos.pieceList[ColorC.WHITE][PieceTypeC.PAWN][0]; stm = pos.sideToMove; } else { wksq = Utils.flip_S(pos.king_square(ColorC.BLACK)); bksq = Utils.flip_S(pos.king_square(ColorC.WHITE)); wpsq = Utils.flip_S(pos.pieceList[ColorC.BLACK][PieceTypeC.PAWN][0]); stm = Utils.flip_C(pos.sideToMove); } if (Utils.file_of(wpsq) >= FileC.FILE_E) { wksq = Utils.mirror(wksq); bksq = Utils.mirror(bksq); wpsq = Utils.mirror(wpsq); } if (KPKPosition.probe_kpk_bitbase(wksq, wpsq, bksq, stm) == 0) return ValueC.VALUE_DRAW; Value result = ValueC.VALUE_KNOWN_WIN + Constants.PawnValueEndgame + Utils.rank_of(wpsq); return strongerSide == pos.sideToMove ? result : -result; }
/// Mate with KX vs K. This function is used to evaluate positions with /// King and plenty of material vs a lone king. It simply gives the /// attacking side a bonus for driving the defending king towards the edge /// of the board, and for keeping the distance between the two kings small. /// KXK internal static Value Endgame_KXK(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(weakerSide) == ValueC.VALUE_ZERO); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == ValueC.VALUE_ZERO); // Stalemate detection with lone king MList mlist = MListBroker.GetObject(); mlist.pos = 0; Movegen.generate_legal(pos, mlist.moves, ref mlist.pos); bool any = mlist.pos > 0; MListBroker.Free(); if (pos.sideToMove == weakerSide && !pos.in_check() && !any) { return ValueC.VALUE_DRAW; } Square winnerKSq = pos.king_square(strongerSide); Square loserKSq = pos.king_square(weakerSide); Value result = pos.non_pawn_material(strongerSide) + pos.piece_count(strongerSide, PieceTypeC.PAWN) * Constants.PawnValueEndgame + MateTable[loserKSq] + DistanceBonus[Utils.square_distance(winnerKSq, loserKSq)]; if (pos.piece_count(strongerSide, PieceTypeC.QUEEN)!=0 || pos.piece_count(strongerSide, PieceTypeC.ROOK)!=0 || pos.bishop_pair(strongerSide)) { result += ValueC.VALUE_KNOWN_WIN; } return strongerSide == pos.sideToMove ? result : -result; }
/// K and a pawn vs K and a pawn. This is done by removing the weakest side's /// pawn and probing the KP vs K bitbase: If the weakest side has a draw without /// the pawn, she probably has at least a draw with the pawn as well. The exception /// is when the stronger side's pawn is far advanced and not on a rook file; in /// this case it is often possible to win (e.g. 8/4k3/3p4/3P4/6K1/8/8/8 w - - 0 1). internal static ScaleFactor Endgame_KPKP(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(strongerSide) == ValueC.VALUE_ZERO); Debug.Assert(pos.non_pawn_material(weakerSide) == ValueC.VALUE_ZERO); Debug.Assert(pos.piece_count(ColorC.WHITE, PieceTypeC.PAWN) == 1); Debug.Assert(pos.piece_count(ColorC.BLACK, PieceTypeC.PAWN) == 1); Square wksq = pos.king_square(strongerSide); Square bksq = pos.king_square(weakerSide); Square wpsq = pos.pieceList[strongerSide][PieceTypeC.PAWN][0]; Color stm = pos.sideToMove; if (strongerSide == ColorC.BLACK) { wksq = Utils.flip_S(wksq); bksq = Utils.flip_S(bksq); wpsq = Utils.flip_S(wpsq); stm = Utils.flip_C(stm); } if (Utils.file_of(wpsq) >= FileC.FILE_E) { wksq = Utils.mirror(wksq); bksq = Utils.mirror(bksq); wpsq = Utils.mirror(wpsq); } // If the pawn has advanced to the fifth rank or further, and is not a // rook pawn, it's too dangerous to assume that it's at least a draw. if (Utils.rank_of(wpsq) >= RankC.RANK_5 && Utils.file_of(wpsq) != FileC.FILE_A) return ScaleFactorC.SCALE_FACTOR_NONE; // Probe the KPK bitbase with the weakest side's pawn removed. If it's a draw, // it's probably at least a draw even with the pawn. return (KPKPosition.probe_kpk_bitbase(wksq, wpsq, bksq, stm) != 0) ? ScaleFactorC.SCALE_FACTOR_NONE : ScaleFactorC.SCALE_FACTOR_DRAW; }
internal static bool is_KBPsKs(int Us, Position pos) { return pos.non_pawn_material(Us) == Constants.BishopValueMidgame && pos.piece_count(Us, PieceTypeC.BISHOP) == 1 && pos.piece_count(Us, PieceTypeC.PAWN) >= 1; }
/// K and two or more pawns vs K. There is just a single rule here: If all pawns /// are on the same rook file and are blocked by the defending king, it's a draw. internal static ScaleFactor Endgame_KPsK(Color strongerSide, Position pos) { Color weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(strongerSide) == ValueC.VALUE_ZERO); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) >= 2); Debug.Assert(pos.non_pawn_material(weakerSide) == ValueC.VALUE_ZERO); Debug.Assert(pos.piece_count(weakerSide, PieceTypeC.PAWN) == 0); Square ksq = pos.king_square(weakerSide); Bitboard pawns = pos.pieces_PTC(PieceTypeC.PAWN, strongerSide); // Are all pawns on the 'a' file? if ((pawns & ~Constants.FileABB) == 0) { // Does the defending king block the pawns? if (Utils.square_distance(ksq, Utils.relative_square(strongerSide, SquareC.SQ_A8)) <= 1 || (Utils.file_of(ksq) == FileC.FILE_A && ((Utils.in_front_bb_CS(strongerSide, ksq)) & pawns) == 0)) return ScaleFactorC.SCALE_FACTOR_DRAW; } // Are all pawns on the 'h' file? else if ((pawns & ~Constants.FileHBB) == 0) { // Does the defending king block the pawns? if (Utils.square_distance(ksq, Utils.relative_square(strongerSide, SquareC.SQ_H8)) <= 1 || (Utils.file_of(ksq) == FileC.FILE_H && ((Utils.in_front_bb_CS(strongerSide, ksq)) & pawns) == 0)) return ScaleFactorC.SCALE_FACTOR_DRAW; } return ScaleFactorC.SCALE_FACTOR_NONE; }
/// MaterialTable::material_info() takes a position object as input, /// computes or looks up a MaterialInfo object, and returns a pointer to it. /// If the material configuration is not already present in the table, it /// is stored there, so we don't have to recompute everything when the /// same material configuration occurs again. internal void probe(Position pos, out MaterialEntry e) { var key = pos.material_key(); e = this.entries[((uint)key) & Constants.MaterialTableMask]; // If mi->key matches the position's material hash key, it means that we // have analysed this material configuration before, and we can simply // return the information we found the last time instead of recomputing it. if (e.key == key) { return; } // Initialize MaterialInfo entry var npm = pos.non_pawn_material(ColorC.WHITE) + pos.non_pawn_material(ColorC.BLACK); e.value = 0; e.scalingFunctionWHITE = null; e.scalingFunctionBLACK = null; e.spaceWeight = 0; e.key = key; e.factorWHITE = e.factorBLACK = ScaleFactorC.SCALE_FACTOR_NORMAL; e.gamePhase = npm >= MidgameLimit ? PhaseC.PHASE_MIDGAME : npm <= EndgameLimit ? PhaseC.PHASE_ENDGAME : (((npm - EndgameLimit) * 128) / (MidgameLimit - EndgameLimit)); // Let's look if we have a specialized evaluation function for this // particular material configuration. First we look for a fixed // configuration one, then a generic one if previous search failed. if ((e.evaluationFunction = Endgame.probeValue(key, out e.evaluationFunctionColor)) != null) { return; } if (is_KXK(ColorC.WHITE, pos)) { e.evaluationFunction = Endgame.Endgame_KXK; e.evaluationFunctionColor = ColorC.WHITE; return; } if (is_KXK(ColorC.BLACK, pos)) { e.evaluationFunction = Endgame.Endgame_KXK; e.evaluationFunctionColor = ColorC.BLACK; return; } if ((pos.pieces_PT(PieceTypeC.PAWN) == 0) && (pos.pieces_PT(PieceTypeC.ROOK) == 0) && (pos.pieces_PT(PieceTypeC.QUEEN) == 0)) { // Minor piece endgame with at least one minor piece per side and // no pawns. Note that the case KmmK is already handled by KXK. Debug.Assert( (pos.pieces_PTC(PieceTypeC.KNIGHT, ColorC.WHITE) | pos.pieces_PTC(PieceTypeC.BISHOP, ColorC.WHITE)) != 0); Debug.Assert( (pos.pieces_PTC(PieceTypeC.KNIGHT, ColorC.BLACK) | pos.pieces_PTC(PieceTypeC.BISHOP, ColorC.BLACK)) != 0); if (pos.piece_count(ColorC.WHITE, PieceTypeC.BISHOP) + pos.piece_count(ColorC.WHITE, PieceTypeC.KNIGHT) <= 2 && pos.piece_count(ColorC.BLACK, PieceTypeC.BISHOP) + pos.piece_count(ColorC.BLACK, PieceTypeC.KNIGHT) <= 2) { e.evaluationFunction = Endgame.Endgame_KmmKm; e.evaluationFunctionColor = pos.sideToMove; return; } } // OK, we didn't find any special evaluation function for the current // material configuration. Is there a suitable scaling function? // // We face problems when there are several conflicting applicable // scaling functions and we need to decide which one to use. EndgameScaleFactor sf; int c; if ((sf = Endgame.probeScaleFactor(key, out c)) != null) { if (c == ColorC.WHITE) { e.scalingFunctionWHITE = sf; } else { e.scalingFunctionBLACK = sf; } return; } // Generic scaling functions that refer to more then one material // distribution. Should be probed after the specialized ones. // Note that these ones don't return after setting the function. if (is_KBPsKs(ColorC.WHITE, pos)) { e.scalingFunctionWHITE = Endgame.Endgame_KBPsK; } if (is_KBPsKs(ColorC.BLACK, pos)) { e.scalingFunctionBLACK = Endgame.Endgame_KBPsK; } if (is_KQKRPs(ColorC.WHITE, pos)) { e.scalingFunctionWHITE = Endgame.Endgame_KQKRPs; } else if (is_KQKRPs(ColorC.BLACK, pos)) { e.scalingFunctionBLACK = Endgame.Endgame_KQKRPs; } var npm_w = pos.non_pawn_material(ColorC.WHITE); var npm_b = pos.non_pawn_material(ColorC.BLACK); if (npm_w + npm_b == ValueC.VALUE_ZERO) { if (pos.piece_count(ColorC.BLACK, PieceTypeC.PAWN) == 0) { Debug.Assert(pos.piece_count(ColorC.WHITE, PieceTypeC.PAWN) >= 2); e.scalingFunctionWHITE = Endgame.Endgame_KPsK; } else if (pos.piece_count(ColorC.WHITE, PieceTypeC.PAWN) == 0) { Debug.Assert(pos.piece_count(ColorC.BLACK, PieceTypeC.PAWN) >= 2); e.scalingFunctionBLACK = Endgame.Endgame_KPsK; } else if (pos.piece_count(ColorC.WHITE, PieceTypeC.PAWN) == 1 && pos.piece_count(ColorC.BLACK, PieceTypeC.PAWN) == 1) { // This is a special case because we set scaling functions // for both colors instead of only one. e.scalingFunctionWHITE = Endgame.Endgame_KPKP; e.scalingFunctionBLACK = Endgame.Endgame_KPKP; } } // No pawns makes it difficult to win, even with a material advantage if (pos.piece_count(ColorC.WHITE, PieceTypeC.PAWN) == 0 && npm_w - npm_b <= Constants.BishopValueMidgame) { e.factorWHITE = (byte) (npm_w == npm_b || npm_w < Constants.RookValueMidgame ? 0 : NoPawnsSF[Math.Min(pos.piece_count(ColorC.WHITE, PieceTypeC.BISHOP), 2)]); } if (pos.piece_count(ColorC.BLACK, PieceTypeC.PAWN) == 0 && npm_b - npm_w <= Constants.BishopValueMidgame) { e.factorBLACK = (byte) (npm_w == npm_b || npm_b < Constants.RookValueMidgame ? 0 : NoPawnsSF[Math.Min(pos.piece_count(ColorC.BLACK, PieceTypeC.BISHOP), 2)]); } // Compute the space weight if (npm_w + npm_b >= 2 * Constants.QueenValueMidgame + 4 * Constants.RookValueMidgame + 2 * Constants.KnightValueMidgame) { var minorPieceCount = pos.piece_count(ColorC.WHITE, PieceTypeC.KNIGHT) + pos.piece_count(ColorC.WHITE, PieceTypeC.BISHOP) + pos.piece_count(ColorC.BLACK, PieceTypeC.KNIGHT) + pos.piece_count(ColorC.BLACK, PieceTypeC.BISHOP); e.spaceWeight = minorPieceCount * minorPieceCount; } // Evaluate the material imbalance. We use PIECE_TYPE_NONE as a place holder // for the bishop pair "extended piece", this allow us to be more flexible // in defining bishop pair bonuses. this.pieceCount[0][0] = pos.piece_count(ColorC.WHITE, PieceTypeC.BISHOP) > 1 ? 1 : 0; this.pieceCount[0][1] = pos.piece_count(ColorC.WHITE, PieceTypeC.PAWN); this.pieceCount[0][2] = pos.piece_count(ColorC.WHITE, PieceTypeC.KNIGHT); this.pieceCount[0][3] = pos.piece_count(ColorC.WHITE, PieceTypeC.BISHOP); this.pieceCount[0][4] = pos.piece_count(ColorC.WHITE, PieceTypeC.ROOK); this.pieceCount[0][5] = pos.piece_count(ColorC.WHITE, PieceTypeC.QUEEN); this.pieceCount[1][0] = pos.piece_count(ColorC.BLACK, PieceTypeC.BISHOP) > 1 ? 1 : 0; this.pieceCount[1][1] = pos.piece_count(ColorC.BLACK, PieceTypeC.PAWN); this.pieceCount[1][2] = pos.piece_count(ColorC.BLACK, PieceTypeC.KNIGHT); this.pieceCount[1][3] = pos.piece_count(ColorC.BLACK, PieceTypeC.BISHOP); this.pieceCount[1][4] = pos.piece_count(ColorC.BLACK, PieceTypeC.ROOK); this.pieceCount[1][5] = pos.piece_count(ColorC.BLACK, PieceTypeC.QUEEN); e.value = (short)((this.imbalance(ColorC.WHITE) - this.imbalance(ColorC.BLACK)) / 16); }
/// K, bishop and one or more pawns vs K. It checks for draws with rook pawns and /// a bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_DRAW /// is returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling /// will be used. internal static int Endgame_KBPsK(int strongerSide, Position pos) { var weakerSide = strongerSide ^ 1; Debug.Assert(pos.non_pawn_material(strongerSide) == Constants.BishopValueMidgame); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.BISHOP) == 1); Debug.Assert(pos.piece_count(strongerSide, PieceTypeC.PAWN) >= 1); // No Debug.Assertions about the material of weakerSide, because we want draws to // be detected even when the weaker side has some pawns. var pawns = pos.pieces_PTC(PieceTypeC.PAWN, strongerSide); var pawnFile = Utils.file_of(pos.pieceList[strongerSide][PieceTypeC.PAWN][0]); // All pawns are on a single rook file ? if ((pawnFile == FileC.FILE_A || pawnFile == FileC.FILE_H) && (((pawns & ~Utils.file_bb_F(pawnFile))) == 0)) { var bishopSq = pos.pieceList[strongerSide][PieceTypeC.BISHOP][0]; var queeningSq = Utils.relative_square(strongerSide, Utils.make_square(pawnFile, RankC.RANK_8)); var kingSq = pos.king_square(weakerSide); if (Utils.opposite_colors(queeningSq, bishopSq) && Math.Abs(Utils.file_of(kingSq) - pawnFile) <= 1) { // The bishop has the wrong color, and the defending king is on the // file of the pawn(s) or the adjacent file. Find the rank of the // frontmost pawn. int rank; if (strongerSide == ColorC.WHITE) { for (rank = RankC.RANK_7; (((Utils.rank_bb_R(rank) & pawns)) == 0); rank--) { } Debug.Assert(rank >= RankC.RANK_2 && rank <= RankC.RANK_7); } else { for (rank = RankC.RANK_2; (((Utils.rank_bb_R(rank) & pawns)) == 0); rank++) { } rank = (rank ^ 7); // HACK to get the relative rank Debug.Assert(rank >= RankC.RANK_2 && rank <= RankC.RANK_7); } // If the defending king has distance 1 to the promotion square or // is placed somewhere in front of the pawn, it's a draw. if (Utils.square_distance(kingSq, queeningSq) <= 1 || Utils.relative_rank_CS(strongerSide, kingSq) >= rank) { return ScaleFactorC.SCALE_FACTOR_DRAW; } } } // All pawns on same B or G file? Then potential draw if ((pawnFile == FileC.FILE_B || pawnFile == FileC.FILE_G) && (pos.pieces_PT(PieceTypeC.PAWN) & ~Utils.file_bb_F(pawnFile)) == 0 && pos.non_pawn_material(weakerSide) == 0 && pos.piece_count(weakerSide, PieceTypeC.PAWN) >= 1) { // Get weaker pawn closest to opponent's queening square Bitboard wkPawns = pos.pieces_PTC(PieceTypeC.PAWN, weakerSide); Square weakerPawnSq = strongerSide == ColorC.WHITE ? Utils.msb(wkPawns) : Utils.lsb(wkPawns); Square strongerKingSq = pos.king_square(strongerSide); Square weakerKingSq = pos.king_square(weakerSide); Square bishopSq = pos.pieceList[strongerSide][PieceTypeC.BISHOP][0]; // Draw if weaker pawn is on rank 7, bishop can't attack the pawn, and // weaker king can stop opposing opponent's king from penetrating. if (Utils.relative_rank_CS(strongerSide, weakerPawnSq) == RankC.RANK_7 && Utils.opposite_colors(bishopSq, weakerPawnSq) && Utils.square_distance(weakerPawnSq, weakerKingSq) <= Utils.square_distance(weakerPawnSq, strongerKingSq)) return ScaleFactorC.SCALE_FACTOR_DRAW; } return ScaleFactorC.SCALE_FACTOR_NONE; }