From: Marco Costalba Date: Sat, 10 Dec 2011 09:14:25 +0000 (+0100) Subject: Fix description of endgame scaling functions X-Git-Url: https://git.sesse.net/?p=stockfish;a=commitdiff_plain;h=14df99130f53a2a5f57260eb830b4c0029bd4e99 Fix description of endgame scaling functions Triggered by a comment of Eelco on talkchess. Also a bit of cleanup while there. No functional change. Signed-off-by: Marco Costalba --- diff --git a/src/endgame.cpp b/src/endgame.cpp index 3082f569..82801317 100644 --- a/src/endgame.cpp +++ b/src/endgame.cpp @@ -60,10 +60,6 @@ namespace { // the two kings in basic endgames. const int DistanceBonus[8] = { 0, 0, 100, 80, 60, 40, 20, 10 }; - // Penalty for big distance between king and knight for the defending king - // and knight in KR vs KN endgames. - const int KRKNKingKnightDistancePenalty[8] = { 0, 0, 4, 10, 20, 32, 48, 70 }; - // Build corresponding key code for the opposite color: "KBPKN" -> "KNKBP" const string swap_colors(const string& keyCode) { @@ -333,14 +329,11 @@ Value Endgame::operator()(const Position& pos) const { assert(pos.piece_count(weakerSide, PAWN) == 0); assert(pos.piece_count(weakerSide, KNIGHT) == 1); - Square defendingKSq = pos.king_square(weakerSide); - Square nSq = pos.piece_list(weakerSide, KNIGHT)[0]; - - int d = square_distance(defendingKSq, nSq); - Value result = Value(10) - + MateTable[defendingKSq] - + KRKNKingKnightDistancePenalty[d]; + const int penalty[8] = { 0, 10, 14, 20, 30, 42, 58, 80 }; + Square bksq = pos.king_square(weakerSide); + Square bnsq = pos.piece_list(weakerSide, KNIGHT)[0]; + Value result = Value(MateTable[bksq] + penalty[square_distance(bksq, bnsq)]); return strongerSide == pos.side_to_move() ? result : -result; } @@ -408,10 +401,9 @@ Value Endgame::operator()(const Position&) const { return VALUE_DRAW; } -/// KBPKScalingFunction scales endgames where the stronger side has king, -/// bishop and one or more pawns. It checks for draws with rook pawns and a -/// bishop of the wrong color. If such a draw is detected, SCALE_FACTOR_ZERO is -/// returned. If not, the return value is SCALE_FACTOR_NONE, i.e. no scaling +/// 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. template<> ScaleFactor Endgame::operator()(const Position& pos) const { @@ -456,17 +448,15 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // is placed somewhere in front of the pawn, it's a draw. if ( square_distance(kingSq, queeningSq) <= 1 || relative_rank(strongerSide, kingSq) >= rank) - return SCALE_FACTOR_ZERO; + return SCALE_FACTOR_DRAW; } } return SCALE_FACTOR_NONE; } -/// KQKRPScalingFunction scales endgames where the stronger side has only -/// king and queen, while the weaker side has at least a rook and a pawn. -/// It tests for fortress draws with a rook on the third rank defended by -/// a pawn. +/// 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. template<> ScaleFactor Endgame::operator()(const Position& pos) const { @@ -485,16 +475,15 @@ ScaleFactor Endgame::operator()(const Position& pos) const { { Square rsq = pos.piece_list(weakerSide, ROOK)[0]; if (pos.attacks_from(rsq, strongerSide) & pos.pieces(PAWN, weakerSide)) - return SCALE_FACTOR_ZERO; + return SCALE_FACTOR_DRAW; } return SCALE_FACTOR_NONE; } -/// KRPKRScalingFunction scales KRP vs KR endgames. 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. +/// 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. @@ -542,7 +531,7 @@ ScaleFactor Endgame::operator()(const Position& pos) const { && square_distance(bksq, queeningSq) <= 1 && wksq <= SQ_H5 && (rank_of(brsq) == RANK_6 || (r <= RANK_3 && rank_of(wrsq) != RANK_6))) - return SCALE_FACTOR_ZERO; + return 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. @@ -550,13 +539,13 @@ ScaleFactor Endgame::operator()(const Position& pos) const { && square_distance(bksq, queeningSq) <= 1 && rank_of(wksq) + tempo <= RANK_6 && (rank_of(brsq) == RANK_1 || (!tempo && abs(file_of(brsq) - f) >= 3))) - return SCALE_FACTOR_ZERO; + return SCALE_FACTOR_DRAW; if ( r >= RANK_6 && bksq == queeningSq && rank_of(brsq) == RANK_1 && (!tempo || square_distance(wksq, wpsq) >= 2)) - return SCALE_FACTOR_ZERO; + return 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. @@ -565,7 +554,7 @@ ScaleFactor Endgame::operator()(const Position& pos) const { && (bksq == SQ_H7 || bksq == SQ_G7) && file_of(brsq) == FILE_A && (rank_of(brsq) <= RANK_3 || file_of(wksq) >= FILE_D || rank_of(wksq) <= RANK_5)) - return SCALE_FACTOR_ZERO; + return SCALE_FACTOR_DRAW; // If the defending king blocks the pawn and the attacking king is too far // away, it's a draw. @@ -573,7 +562,7 @@ ScaleFactor Endgame::operator()(const Position& pos) const { && bksq == wpsq + DELTA_N && square_distance(wksq, wpsq) - tempo >= 2 && square_distance(wksq, brsq) - tempo >= 2) - return SCALE_FACTOR_ZERO; + return 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, @@ -613,8 +602,8 @@ ScaleFactor Endgame::operator()(const Position& pos) const { } -/// KRPPKRPScalingFunction scales KRPP vs KRP endgames. There is only a -/// single pattern: If the stronger side has no pawns and the defending king +/// 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. template<> ScaleFactor Endgame::operator()(const Position& pos) const { @@ -652,9 +641,8 @@ ScaleFactor Endgame::operator()(const Position& pos) const { } -/// KPsKScalingFunction scales endgames with king and two or more pawns -/// against king. 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. +/// 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. template<> ScaleFactor Endgame::operator()(const Position& pos) const { @@ -673,7 +661,7 @@ ScaleFactor Endgame::operator()(const Position& pos) const { if ( square_distance(ksq, relative_square(strongerSide, SQ_A8)) <= 1 || ( file_of(ksq) == FILE_A && !in_front_bb(strongerSide, ksq) & pawns)) - return SCALE_FACTOR_ZERO; + return SCALE_FACTOR_DRAW; } // Are all pawns on the 'h' file? else if (!(pawns & ~FileHBB)) @@ -682,17 +670,16 @@ ScaleFactor Endgame::operator()(const Position& pos) const { if ( square_distance(ksq, relative_square(strongerSide, SQ_H8)) <= 1 || ( file_of(ksq) == FILE_H && !in_front_bb(strongerSide, ksq) & pawns)) - return SCALE_FACTOR_ZERO; + return SCALE_FACTOR_DRAW; } return SCALE_FACTOR_NONE; } -/// KBPKBScalingFunction scales KBP vs KB endgames. 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. +/// 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. template<> ScaleFactor Endgame::operator()(const Position& pos) const { @@ -713,7 +700,7 @@ ScaleFactor Endgame::operator()(const Position& pos) const { && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq) && ( opposite_colors(weakerKingSq, strongerBishopSq) || relative_rank(strongerSide, weakerKingSq) <= RANK_6)) - return SCALE_FACTOR_ZERO; + return SCALE_FACTOR_DRAW; // Case 2: Opposite colored bishops if (opposite_colors(strongerBishopSq, weakerBishopSq)) @@ -729,25 +716,25 @@ ScaleFactor Endgame::operator()(const Position& pos) const { // reasonably well. if (relative_rank(strongerSide, pawnSq) <= RANK_5) - return SCALE_FACTOR_ZERO; + return SCALE_FACTOR_DRAW; else { Bitboard path = squares_in_front_of(strongerSide, pawnSq); if (path & pos.pieces(KING, weakerSide)) - return SCALE_FACTOR_ZERO; + return SCALE_FACTOR_DRAW; if ( (pos.attacks_from(weakerBishopSq) & path) && square_distance(weakerBishopSq, pawnSq) >= 3) - return SCALE_FACTOR_ZERO; + return SCALE_FACTOR_DRAW; } } return SCALE_FACTOR_NONE; } -/// KBPPKBScalingFunction scales KBPP vs KB endgames. It detects a few basic -/// draws with opposite-colored bishops. +/// K, bishop and two pawns vs K and bishop. It detects a few basic draws with +/// opposite-colored bishops. template<> ScaleFactor Endgame::operator()(const Position& pos) const { @@ -790,7 +777,7 @@ ScaleFactor Endgame::operator()(const Position& pos) const { if ( file_of(ksq) == file_of(blockSq1) && relative_rank(strongerSide, ksq) >= relative_rank(strongerSide, blockSq1) && opposite_colors(ksq, wbsq)) - return SCALE_FACTOR_ZERO; + return SCALE_FACTOR_DRAW; else return SCALE_FACTOR_NONE; @@ -803,13 +790,13 @@ ScaleFactor Endgame::operator()(const Position& pos) const { && ( bbsq == blockSq2 || (pos.attacks_from(blockSq2) & pos.pieces(BISHOP, weakerSide)) || abs(r1 - r2) >= 2)) - return SCALE_FACTOR_ZERO; + return SCALE_FACTOR_DRAW; else if ( ksq == blockSq2 && opposite_colors(ksq, wbsq) && ( bbsq == blockSq1 || (pos.attacks_from(blockSq1) & pos.pieces(BISHOP, weakerSide)))) - return SCALE_FACTOR_ZERO; + return SCALE_FACTOR_DRAW; else return SCALE_FACTOR_NONE; @@ -820,10 +807,9 @@ ScaleFactor Endgame::operator()(const Position& pos) const { } -/// KBPKNScalingFunction scales KBP vs KN endgames. 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. +/// K, bisop 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. template<> ScaleFactor Endgame::operator()(const Position& pos) const { @@ -842,15 +828,15 @@ ScaleFactor Endgame::operator()(const Position& pos) const { && relative_rank(strongerSide, pawnSq) < relative_rank(strongerSide, weakerKingSq) && ( opposite_colors(weakerKingSq, strongerBishopSq) || relative_rank(strongerSide, weakerKingSq) <= RANK_6)) - return SCALE_FACTOR_ZERO; + return SCALE_FACTOR_DRAW; return SCALE_FACTOR_NONE; } -/// KNPKScalingFunction scales KNP vs K endgames. 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. +/// 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. template<> ScaleFactor Endgame::operator()(const Position& pos) const { @@ -865,22 +851,21 @@ ScaleFactor Endgame::operator()(const Position& pos) const { if ( pawnSq == relative_square(strongerSide, SQ_A7) && square_distance(weakerKingSq, relative_square(strongerSide, SQ_A8)) <= 1) - return SCALE_FACTOR_ZERO; + return SCALE_FACTOR_DRAW; if ( pawnSq == relative_square(strongerSide, SQ_H7) && square_distance(weakerKingSq, relative_square(strongerSide, SQ_H8)) <= 1) - return SCALE_FACTOR_ZERO; + return SCALE_FACTOR_DRAW; return SCALE_FACTOR_NONE; } -/// KPKPScalingFunction scales KP vs KP endgames. 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). +/// 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). template<> ScaleFactor Endgame::operator()(const Position& pos) const { @@ -889,22 +874,17 @@ ScaleFactor Endgame::operator()(const Position& pos) const { assert(pos.piece_count(WHITE, PAWN) == 1); assert(pos.piece_count(BLACK, PAWN) == 1); - Square wksq, bksq, wpsq; - Color stm; + Square wksq = pos.king_square(strongerSide); + Square bksq = pos.king_square(weakerSide); + Square wpsq = pos.piece_list(strongerSide, PAWN)[0]; + Color stm = pos.side_to_move(); - if (strongerSide == WHITE) - { - wksq = pos.king_square(WHITE); - bksq = pos.king_square(BLACK); - wpsq = pos.piece_list(WHITE, PAWN)[0]; - stm = pos.side_to_move(); - } - else + if (strongerSide == BLACK) { - wksq = flip(pos.king_square(BLACK)); - bksq = flip(pos.king_square(WHITE)); - wpsq = flip(pos.piece_list(BLACK, PAWN)[0]); - stm = flip(pos.side_to_move()); + wksq = flip(wksq); + bksq = flip(bksq); + wpsq = flip(wpsq); + stm = flip(stm); } if (file_of(wpsq) >= FILE_E) @@ -920,7 +900,7 @@ ScaleFactor Endgame::operator()(const Position& pos) const { && file_of(wpsq) != FILE_A) return 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 probe_kpk_bitbase(wksq, wpsq, bksq, stm) ? SCALE_FACTOR_NONE : SCALE_FACTOR_ZERO; + // 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 probe_kpk_bitbase(wksq, wpsq, bksq, stm) ? SCALE_FACTOR_NONE : SCALE_FACTOR_DRAW; } diff --git a/src/material.cpp b/src/material.cpp index 6171c70a..27a88f86 100644 --- a/src/material.cpp +++ b/src/material.cpp @@ -143,7 +143,7 @@ MaterialInfo* MaterialInfoTable::get_material_info(const Position& pos) const { if ( pos.piece_count(WHITE, BISHOP) + pos.piece_count(WHITE, KNIGHT) <= 2 && pos.piece_count(BLACK, BISHOP) + pos.piece_count(BLACK, KNIGHT) <= 2) { - mi->evaluationFunction = &EvaluateKmmKm[WHITE]; + mi->evaluationFunction = &EvaluateKmmKm[pos.side_to_move()]; return mi; } } diff --git a/src/types.h b/src/types.h index b5898b25..d9efb6e8 100644 --- a/src/types.h +++ b/src/types.h @@ -287,7 +287,7 @@ enum SquareColor { }; enum ScaleFactor { - SCALE_FACTOR_ZERO = 0, + SCALE_FACTOR_DRAW = 0, SCALE_FACTOR_NORMAL = 64, SCALE_FACTOR_MAX = 128, SCALE_FACTOR_NONE = 255