X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=3ce896309f530f057daeacf6320bb35d9eb26517;hp=67bf59d183325a52fd2cfc3a200a5d0e60d18f7b;hb=fb8095718bd0789d2743fa6216c6aa522555dc4b;hpb=6d8f583af26daa1c158324d5c13cf01b17c746a5 diff --git a/src/pawns.cpp b/src/pawns.cpp index 67bf59d1..3ce89630 100644 --- a/src/pawns.cpp +++ b/src/pawns.cpp @@ -2,7 +2,7 @@ Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad - Copyright (C) 2015-2018 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad + Copyright (C) 2015-2020 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -31,151 +31,136 @@ namespace { #define V Value #define S(mg, eg) make_score(mg, eg) - // Isolated pawn penalty - const Score Isolated = S(13, 18); - - // Backward pawn penalty - const Score Backward = S(24, 12); - - // Connected pawn bonus by opposed, phalanx, #support and rank - Score Connected[2][2][3][RANK_NB]; - - // Doubled pawn penalty - const Score Doubled = S(18, 38); - - // Weakness of our pawn shelter in front of the king by [isKingFile][distance from edge][rank]. - // RANK_1 = 0 is used for files where we have no pawns or our pawn is behind our king. - const Value ShelterWeakness[][int(FILE_NB) / 2][RANK_NB] = { - { { V( 98), V(20), V(11), V(42), V( 83), V( 84), V(101) }, // Not On King file - { V(103), V( 8), V(33), V(86), V( 87), V(105), V(113) }, - { V(100), V( 2), V(65), V(95), V( 59), V( 89), V(115) }, - { V( 72), V( 6), V(52), V(74), V( 83), V( 84), V(112) } }, - { { V(105), V(19), V( 3), V(27), V( 85), V( 93), V( 84) }, // On King file - { V(121), V( 7), V(33), V(95), V(112), V( 86), V( 72) }, - { V(121), V(26), V(65), V(90), V( 65), V( 76), V(117) }, - { V( 79), V( 0), V(45), V(65), V( 94), V( 92), V(105) } } + // Pawn penalties + constexpr Score Backward = S( 9, 24); + constexpr Score Doubled = S(11, 56); + constexpr Score Isolated = S( 5, 15); + constexpr Score WeakLever = S( 0, 56); + constexpr Score WeakUnopposed = S(13, 27); + + constexpr Score BlockedStorm[RANK_NB] = {S( 0, 0), S( 0, 0), S( 76, 78), S(-10, 15), S(-7, 10), S(-4, 6), S(-1, 2)}; + + // Connected pawn bonus + constexpr int Connected[RANK_NB] = { 0, 7, 8, 12, 29, 48, 86 }; + + // Strength of pawn shelter for our king by [distance from edge][rank]. + // RANK_1 = 0 is used for files where we have no pawn, or pawn is behind our king. + constexpr Value ShelterStrength[int(FILE_NB) / 2][RANK_NB] = { + { V( -6), V( 81), V( 93), V( 58), V( 39), V( 18), V( 25) }, + { V(-43), V( 61), V( 35), V(-49), V(-29), V(-11), V( -63) }, + { V(-10), V( 75), V( 23), V( -2), V( 32), V( 3), V( -45) }, + { V(-39), V(-13), V(-29), V(-52), V(-48), V(-67), V(-166) } }; - // Danger of enemy pawns moving toward our king by [type][distance from edge][rank]. - // For the unopposed and unblocked cases, RANK_1 = 0 is used when opponent has - // no pawn on the given file, or their pawn is behind our king. - const Value StormDanger[][4][RANK_NB] = { - { { V( 0), V(-290), V(-274), V(57), V(41) }, // BlockedByKing - { V( 0), V( 60), V( 144), V(39), V(13) }, - { V( 0), V( 65), V( 141), V(41), V(34) }, - { V( 0), V( 53), V( 127), V(56), V(14) } }, - { { V( 4), V( 73), V( 132), V(46), V(31) }, // Unopposed - { V( 1), V( 64), V( 143), V(26), V(13) }, - { V( 1), V( 47), V( 110), V(44), V(24) }, - { V( 0), V( 72), V( 127), V(50), V(31) } }, - { { V( 0), V( 0), V( 79), V(23), V( 1) }, // BlockedByPawn - { V( 0), V( 0), V( 148), V(27), V( 2) }, - { V( 0), V( 0), V( 161), V(16), V( 1) }, - { V( 0), V( 0), V( 171), V(22), V(15) } }, - { { V(22), V( 45), V( 104), V(62), V( 6) }, // Unblocked - { V(31), V( 30), V( 99), V(39), V(19) }, - { V(23), V( 29), V( 96), V(41), V(15) }, - { V(21), V( 23), V( 116), V(41), V(15) } } + // Danger of enemy pawns moving toward our king by [distance from edge][rank]. + // RANK_1 = 0 is used for files where the enemy has no pawn, or their pawn + // is behind our king. Note that UnblockedStorm[0][1-2] accommodate opponent pawn + // on edge, likely blocked by our king. + constexpr Value UnblockedStorm[int(FILE_NB) / 2][RANK_NB] = { + { V( 85), V(-289), V(-166), V(97), V(50), V( 45), V( 50) }, + { V( 46), V( -25), V( 122), V(45), V(37), V(-10), V( 20) }, + { V( -6), V( 51), V( 168), V(34), V(-2), V(-22), V(-14) }, + { V(-15), V( -11), V( 101), V( 4), V(11), V(-15), V(-29) } }; - // Max bonus for king safety. Corresponds to start position with all the pawns - // in front of the king and no enemy pawn on the horizon. - const Value MaxSafetyBonus = V(258); - #undef S #undef V template Score evaluate(const Position& pos, Pawns::Entry* e) { - const Color Them = (Us == WHITE ? BLACK : WHITE); - const Direction Up = (Us == WHITE ? NORTH : SOUTH); + constexpr Color Them = ~Us; + constexpr Direction Up = pawn_push(Us); - Bitboard b, neighbours, stoppers, doubled, supported, phalanx; - Bitboard lever, leverPush; + Bitboard neighbours, stoppers, support, phalanx, opposed; + Bitboard lever, leverPush, blocked; Square s; - bool opposed, backward; + bool backward, passed, doubled; Score score = SCORE_ZERO; const Square* pl = pos.squares(Us); Bitboard ourPawns = pos.pieces( Us, PAWN); Bitboard theirPawns = pos.pieces(Them, PAWN); - e->passedPawns[Us] = e->pawnAttacksSpan[Us] = e->weakUnopposed[Us] = 0; - e->semiopenFiles[Us] = 0xFF; - e->kingSquares[Us] = SQ_NONE; - e->pawnAttacks[Us] = pawn_attacks_bb(ourPawns); - e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares); - e->pawnsOnSquares[Us][WHITE] = pos.count(Us) - e->pawnsOnSquares[Us][BLACK]; + Bitboard doubleAttackThem = pawn_double_attacks_bb(theirPawns); + + e->passedPawns[Us] = 0; + e->kingSquares[Us] = SQ_NONE; + e->pawnAttacks[Us] = e->pawnAttacksSpan[Us] = pawn_attacks_bb(ourPawns); + e->blockedCount += popcount(shift(ourPawns) & (theirPawns | doubleAttackThem)); // Loop through all pawns of the current color and score each pawn while ((s = *pl++) != SQ_NONE) { assert(pos.piece_on(s) == make_piece(Us, PAWN)); - File f = file_of(s); - - e->semiopenFiles[Us] &= ~(1 << f); - e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s); + Rank r = relative_rank(Us, s); // Flag the pawn opposed = theirPawns & forward_file_bb(Us, s); - stoppers = theirPawns & passed_pawn_mask(Us, s); + blocked = theirPawns & (s + Up); + stoppers = theirPawns & passed_pawn_span(Us, s); lever = theirPawns & PawnAttacks[Us][s]; leverPush = theirPawns & PawnAttacks[Us][s + Up]; doubled = ourPawns & (s - Up); - neighbours = ourPawns & adjacent_files_bb(f); + neighbours = ourPawns & adjacent_files_bb(s); phalanx = neighbours & rank_bb(s); - supported = neighbours & rank_bb(s - Up); + support = neighbours & rank_bb(s - Up); + + // A pawn is backward when it is behind all pawns of the same color on + // the adjacent files and cannot safely advance. + backward = !(neighbours & forward_ranks_bb(Them, s + Up)) + && (leverPush | blocked); + + // Compute additional span if pawn is not backward nor blocked + if (!backward && !blocked) + e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s); + + // A pawn is passed if one of the three following conditions is true: + // (a) there is no stoppers except some levers + // (b) the only stoppers are the leverPush, but we outnumber them + // (c) there is only one front stopper which can be levered. + // (Refined in Evaluation::passed) + passed = !(stoppers ^ lever) + || ( !(stoppers ^ leverPush) + && popcount(phalanx) >= popcount(leverPush)) + || ( stoppers == blocked && r >= RANK_5 + && (shift(support) & ~(theirPawns | doubleAttackThem))); + + passed &= !(forward_file_bb(Us, s) & ourPawns); + + // Passed pawns will be properly scored later in evaluation when we have + // full attack info. + if (passed) + e->passedPawns[Us] |= s; - // A pawn is backward when it is behind all pawns of the same color on the - // adjacent files and cannot be safely advanced. - if (!neighbours || lever || relative_rank(Us, s) >= RANK_5) - backward = false; - else + // Score this pawn + if (support | phalanx) { - // Find the backmost rank with neighbours or stoppers - b = rank_bb(backmost_sq(Us, neighbours | stoppers)); + int v = Connected[r] * (4 + 2 * bool(phalanx) - 2 * bool(opposed) - bool(blocked)) / 2 + + 21 * popcount(support); - // The pawn is backward when it cannot safely progress to that rank: - // either there is a stopper in the way on this rank, or there is a - // stopper on adjacent file which controls the way to that rank. - backward = (b | shift(b & adjacent_files_bb(f))) & stoppers; - - assert(!(backward && (forward_ranks_bb(Them, s + Up) & neighbours))); + score += make_score(v, v * (r - 2) / 4); } - // Passed pawns will be properly scored in evaluation because we need - // full attack info to evaluate them. Include also not passed pawns - // which could become passed after one or two pawn pushes when are - // not attacked more times than defended. - if ( !(stoppers ^ lever ^ leverPush) - && !(ourPawns & forward_file_bb(Us, s)) - && popcount(supported) >= popcount(lever) - && popcount(phalanx) >= popcount(leverPush)) - e->passedPawns[Us] |= s; - - else if ( stoppers == SquareBB[s + Up] - && relative_rank(Us, s) >= RANK_5) + else if (!neighbours) { - b = shift(supported) & ~theirPawns; - while (b) - if (!more_than_one(theirPawns & PawnAttacks[Us][pop_lsb(&b)])) - e->passedPawns[Us] |= s; - } - - // Score this pawn - if (supported | phalanx) - score += Connected[opposed][bool(phalanx)][popcount(supported)][relative_rank(Us, s)]; + score -= Isolated + + WeakUnopposed * !opposed; - else if (!neighbours) - score -= Isolated, e->weakUnopposed[Us] += !opposed; + if ( (ourPawns & forward_file_bb(Them, s)) + && popcount(opposed) == 1 + && !(theirPawns & adjacent_files_bb(s))) + score -= Doubled; + } else if (backward) - score -= Backward, e->weakUnopposed[Us] += !opposed; + score -= Backward + + WeakUnopposed * !opposed; - if (doubled && !supported) - score -= Doubled; + if (!support) + score -= Doubled * doubled + + WeakLever * more_than_one(lever); } return score; @@ -185,27 +170,6 @@ namespace { namespace Pawns { -/// Pawns::init() initializes some tables needed by evaluation. Instead of using -/// hard-coded tables, when makes sense, we prefer to calculate them with a formula -/// to reduce independent parameters and to allow easier tuning and better insight. - -void init() { - - static const int Seed[RANK_NB] = { 0, 13, 24, 18, 76, 100, 175, 330 }; - - for (int opposed = 0; opposed <= 1; ++opposed) - for (int phalanx = 0; phalanx <= 1; ++phalanx) - for (int support = 0; support <= 2; ++support) - for (Rank r = RANK_2; r < RANK_8; ++r) - { - int v = 17 * support; - v += (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed; - - Connected[opposed][phalanx][support][r] = make_score(v, v * (r - 2) / 4); - } -} - - /// Pawns::probe() looks up the current position's pawns configuration in /// the pawns hash table. It returns a pointer to the Entry if the position /// is found. Otherwise a new Entry is computed and stored there, so we don't @@ -220,61 +184,47 @@ Entry* probe(const Position& pos) { return e; e->key = key; + e->blockedCount = 0; e->scores[WHITE] = evaluate(pos, e); e->scores[BLACK] = evaluate(pos, e); - e->openFiles = popcount(e->semiopenFiles[WHITE] & e->semiopenFiles[BLACK]); - e->asymmetry = popcount( (e->passedPawns[WHITE] | e->passedPawns[BLACK]) - | (e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK])); return e; } -/// Entry::shelter_storm() calculates shelter and storm penalties for the file -/// the king is on, as well as the two closest files. +/// Entry::evaluate_shelter() calculates the shelter bonus and the storm +/// penalty for a king, looking at the king file and the two closest files. template -Value Entry::shelter_storm(const Position& pos, Square ksq) { - - constexpr Color Them = (Us == WHITE ? BLACK : WHITE); - constexpr Bitboard ShelterMask = - Us == WHITE ? make_bitboard(SQ_A2, SQ_B3, SQ_C2, SQ_F2, SQ_G3, SQ_H2) - : make_bitboard(SQ_A7, SQ_B6, SQ_C7, SQ_F7, SQ_G6, SQ_H7); - constexpr Bitboard StormMask = - Us == WHITE ? make_bitboard(SQ_A3, SQ_C3, SQ_F3, SQ_H3) - : make_bitboard(SQ_A6, SQ_C6, SQ_F6, SQ_H6); - - enum { BlockedByKing, Unopposed, BlockedByPawn, Unblocked }; - - File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq))); - Bitboard b = pos.pieces(PAWN) - & (forward_ranks_bb(Us, ksq) | rank_bb(ksq)) - & (adjacent_files_bb(center) | file_bb(center)); - Bitboard ourPawns = b & pos.pieces(Us); +Score Entry::evaluate_shelter(const Position& pos, Square ksq) { + + constexpr Color Them = ~Us; + + Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq); + Bitboard ourPawns = b & pos.pieces(Us) & ~pawnAttacks[Them]; Bitboard theirPawns = b & pos.pieces(Them); - Value safety = MaxSafetyBonus; + Score bonus = make_score(5, 5); + + File center = Utility::clamp(file_of(ksq), FILE_B, FILE_G); for (File f = File(center - 1); f <= File(center + 1); ++f) { b = ourPawns & file_bb(f); - Rank rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1; + int ourRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0; b = theirPawns & file_bb(f); - Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1; - - int d = std::min(f, ~f); - safety -= ShelterWeakness[f == file_of(ksq)][d][rkUs] - + StormDanger - [f == file_of(ksq) && rkThem == relative_rank(Us, ksq) + 1 ? BlockedByKing : - rkUs == RANK_1 ? Unopposed : - rkThem == rkUs + 1 ? BlockedByPawn : Unblocked] - [d][rkThem]; - } + int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0; - if (popcount((ourPawns & ShelterMask) | (theirPawns & StormMask)) == 5) - safety += Value(300); + int d = edge_distance(f); + bonus += make_score(ShelterStrength[d][ourRank], 0); + + if (ourRank && (ourRank == theirRank - 1)) + bonus -= BlockedStorm[theirRank]; + else + bonus -= make_score(UnblockedStorm[d][theirRank], 0); + } - return safety; + return bonus; } @@ -282,30 +232,37 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) { /// when king square changes, which is about 20% of total king_safety() calls. template -Score Entry::do_king_safety(const Position& pos, Square ksq) { +Score Entry::do_king_safety(const Position& pos) { + Square ksq = pos.square(Us); kingSquares[Us] = ksq; - castlingRights[Us] = pos.can_castle(Us); - int minKingPawnDistance = 0; + castlingRights[Us] = pos.castling_rights(Us); + auto compare = [](Score a, Score b) { return mg_value(a) < mg_value(b); }; - Bitboard pawns = pos.pieces(Us, PAWN); - if (pawns) - while (!(DistanceRingBB[ksq][minKingPawnDistance++] & pawns)) {} + Score shelter = evaluate_shelter(pos, ksq); + + // If we can castle use the bonus after castling if it is bigger - Value bonus = shelter_storm(pos, ksq); + if (pos.can_castle(Us & KING_SIDE)) + shelter = std::max(shelter, evaluate_shelter(pos, relative_square(Us, SQ_G1)), compare); - // If we can castle use the bonus after the castling if it is bigger - if (pos.can_castle(MakeCastling::right)) - bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_G1))); + if (pos.can_castle(Us & QUEEN_SIDE)) + shelter = std::max(shelter, evaluate_shelter(pos, relative_square(Us, SQ_C1)), compare); + + // In endgame we like to bring our king near our closest pawn + Bitboard pawns = pos.pieces(Us, PAWN); + int minPawnDist = 6; - if (pos.can_castle(MakeCastling::right)) - bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1))); + if (pawns & PseudoAttacks[KING][ksq]) + minPawnDist = 1; + else while (pawns) + minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns))); - return make_score(bonus, -16 * minKingPawnDistance); + return shelter - make_score(0, 16 * minPawnDist); } // Explicit template instantiation -template Score Entry::do_king_safety(const Position& pos, Square ksq); -template Score Entry::do_king_safety(const Position& pos, Square ksq); +template Score Entry::do_king_safety(const Position& pos); +template Score Entry::do_king_safety(const Position& pos); } // namespace Pawns