X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=c8c2e6d8c243db77d67b30afd109dfd2ea1fff4f;hp=eeabcbae84df6e81ed22a5bbff8c5c1b684cb1fd;hb=471f7a1b5c4da03a712da2ce079034de45b4c35b;hpb=cc2b3ece5c5d8d1183f8526fbb0ee4e1ea7a69fe diff --git a/src/pawns.cpp b/src/pawns.cpp index eeabcbae..fb91afcb 100644 --- a/src/pawns.cpp +++ b/src/pawns.cpp @@ -1,7 +1,8 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2015-2017 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 @@ -17,263 +18,284 @@ along with this program. If not, see . */ +#include #include #include "bitboard.h" -#include "bitcount.h" #include "pawns.h" #include "position.h" +#include "thread.h" namespace { + #define V Value #define S(mg, eg) make_score(mg, eg) - // Doubled pawn penalty by opposed flag and file - const Score DoubledPawnPenalty[2][8] = { - { S(13, 43), S(20, 48), S(23, 48), S(23, 48), - S(23, 48), S(23, 48), S(20, 48), S(13, 43) }, - { S(13, 43), S(20, 48), S(23, 48), S(23, 48), - S(23, 48), S(23, 48), S(20, 48), S(13, 43) }}; - - // Isolated pawn penalty by opposed flag and file - const Score IsolatedPawnPenalty[2][8] = { - { S(37, 45), S(54, 52), S(60, 52), S(60, 52), - S(60, 52), S(60, 52), S(54, 52), S(37, 45) }, - { S(25, 30), S(36, 35), S(40, 35), S(40, 35), - S(40, 35), S(40, 35), S(36, 35), S(25, 30) }}; - - // Backward pawn penalty by opposed flag and file - const Score BackwardPawnPenalty[2][8] = { - { S(30, 42), S(43, 46), S(49, 46), S(49, 46), - S(49, 46), S(49, 46), S(43, 46), S(30, 42) }, - { S(20, 28), S(29, 31), S(33, 31), S(33, 31), - S(33, 31), S(33, 31), S(29, 31), S(20, 28) }}; - - // Pawn chain membership bonus by file - const Score ChainBonus[8] = { - S(11,-1), S(13,-1), S(13,-1), S(14,-1), - S(14,-1), S(13,-1), S(13,-1), S(11,-1) - }; + // Isolated pawn penalty by opposed flag + const Score Isolated[2] = { S(45, 40), S(30, 27) }; + + // Backward pawn penalty by opposed flag + const Score Backward[2] = { S(56, 33), S(41, 19) }; + + // Unsupported pawn penalty for pawns which are neither isolated or backward + const Score Unsupported = S(17, 8); + + // Connected pawn bonus by opposed, phalanx, twice supported and rank + Score Connected[2][2][2][RANK_NB]; - // Candidate passed pawn bonus by rank - const Score CandidateBonus[8] = { - S( 0, 0), S( 6, 13), S(6,13), S(14,29), - S(34,68), S(83,166), S(0, 0), S( 0, 0) + // Doubled pawn penalty + const Score Doubled = S(18, 38); + + // Lever bonus by rank + const Score Lever[RANK_NB] = { + S( 0, 0), S( 0, 0), S(0, 0), S(0, 0), + S(17, 16), S(33, 32), S(0, 0), S(0, 0) }; - const Score PawnStructureWeight = S(233, 201); + // Weakness of our pawn shelter in front of the king by [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[][RANK_NB] = { + { V(100), V(20), V(10), V(46), V(82), V( 86), V( 98) }, + { V(116), V( 4), V(28), V(87), V(94), V(108), V(104) }, + { V(109), V( 1), V(59), V(87), V(62), V( 91), V(116) }, + { V( 75), V(12), V(43), V(59), V(90), V( 84), V(112) } + }; - #undef S + // 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) } } + }; - const File ShelterFile[8] = { FILE_B, FILE_B, FILE_C, FILE_D, FILE_E, FILE_F, FILE_G, FILE_G }; + // 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); - inline Value score_non_center_file(const Value v) { - return Value(v * 7 / 16); + #undef S + #undef V + + template + Score evaluate(const Position& pos, Pawns::Entry* e) { + + const Color Them = (Us == WHITE ? BLACK : WHITE); + const Square Up = (Us == WHITE ? NORTH : SOUTH); + const Square Right = (Us == WHITE ? NORTH_EAST : SOUTH_WEST); + const Square Left = (Us == WHITE ? NORTH_WEST : SOUTH_EAST); + + Bitboard b, neighbours, stoppers, doubled, supported, phalanx; + Bitboard lever, leverPush, connected; + Square s; + bool opposed, backward; + Score score = SCORE_ZERO; + const Square* pl = pos.squares(Us); + const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)]; + + Bitboard ourPawns = pos.pieces(Us , PAWN); + Bitboard theirPawns = pos.pieces(Them, PAWN); + + e->passedPawns[Us] = e->pawnAttacksSpan[Us] = 0; + e->semiopenFiles[Us] = 0xFF; + e->kingSquares[Us] = SQ_NONE; + e->pawnAttacks[Us] = shift(ourPawns) | shift(ourPawns); + e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares); + e->pawnsOnSquares[Us][WHITE] = pos.count(Us) - e->pawnsOnSquares[Us][BLACK]; + + // 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); + + // Flag the pawn + opposed = theirPawns & forward_bb(Us, s); + stoppers = theirPawns & passed_pawn_mask(Us, s); + lever = theirPawns & pawnAttacksBB[s]; + leverPush = theirPawns & pawnAttacksBB[s + Up]; + doubled = ourPawns & (s + Up); + neighbours = ourPawns & adjacent_files_bb(f); + phalanx = neighbours & rank_bb(s); + supported = neighbours & rank_bb(s - Up); + connected = supported | phalanx; + + // 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 + { + // Find the backmost rank with neighbours or stoppers + b = rank_bb(backmost_sq(Us, neighbours | stoppers)); + + // 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 || !(pawn_attack_span(Them, s + Up) & neighbours)); + } + + // 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_bb(Us, s)) + && popcount(supported) >= popcount(lever) + && popcount(phalanx) >= popcount(leverPush)) + e->passedPawns[Us] |= s; + + // Score this pawn + if (!neighbours) + score -= Isolated[opposed]; + + else if (backward) + score -= Backward[opposed]; + + else if (!supported) + score -= Unsupported; + + if (connected) + score += Connected[opposed][!!phalanx][more_than_one(supported)][relative_rank(Us, s)]; + + if (doubled) + score -= Doubled; + + if (lever) + score += Lever[relative_rank(Us, s)]; + } + + return score; } - typedef Value V; - // Arrays are indexed by rank. Zeroth value is for when no pawn on that file. - const Value PawnShelter[8] = { V(141), V(0), V( 38), V(102), V(128), V(141), V(141), V(141) }; - const Value PawnStorm[8] = { V( 26), V(0), V(128), V( 51), V( 26), V( 0), V( 0), V( 0) }; - // We compute shelter as a penalty for the given color, but shelter is used as a bonus, so we invert it using this as the basis. - const Value PawnShelterBasis = PawnShelter[0] + score_non_center_file(PawnShelter[0]) * 2; +} // namespace - inline Score apply_weight(Score v, Score w) { - return make_score((int(mg_value(v)) * mg_value(w)) / 0x100, - (int(eg_value(v)) * eg_value(w)) / 0x100); - } -} +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. -/// PawnInfoTable::pawn_info() takes a position object as input, computes -/// a PawnInfo object, and returns a pointer to it. The result is also stored -/// in an hash table, so we don't have to recompute everything when the same -/// pawn structure occurs again. +void init() { -PawnInfo* PawnInfoTable::pawn_info(const Position& pos) const { + static const int Seed[RANK_NB] = { 0, 8, 19, 13, 71, 94, 169, 324 }; - Key key = pos.pawn_key(); - PawnInfo* pi = probe(key); + for (int opposed = 0; opposed <= 1; ++opposed) + for (int phalanx = 0; phalanx <= 1; ++phalanx) + for (int apex = 0; apex <= 1; ++apex) + for (Rank r = RANK_2; r < RANK_8; ++r) + { + int v = (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed; + v += (apex ? v / 2 : 0); + Connected[opposed][phalanx][apex][r] = make_score(v, v * (r-2) / 4); + } +} - // If pi->key matches the position's pawn hash key, it means that we - // have analysed this pawn structure before, and we can simply return - // the information we found the last time instead of recomputing it. - if (pi->key == key) - return pi; - // Initialize PawnInfo entry - pi->key = key; - pi->passedPawns[WHITE] = pi->passedPawns[BLACK] = 0; - pi->kingSquares[WHITE] = pi->kingSquares[BLACK] = SQ_NONE; - pi->halfOpenFiles[WHITE] = pi->halfOpenFiles[BLACK] = 0xFF; +/// 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 +/// have to recompute all when the same pawns configuration occurs again. - // Calculate pawn attacks - Bitboard wPawns = pos.pieces(PAWN, WHITE); - Bitboard bPawns = pos.pieces(PAWN, BLACK); - pi->pawnAttacks[WHITE] = ((wPawns << 9) & ~FileABB) | ((wPawns << 7) & ~FileHBB); - pi->pawnAttacks[BLACK] = ((bPawns >> 7) & ~FileABB) | ((bPawns >> 9) & ~FileHBB); +Entry* probe(const Position& pos) { - // Evaluate pawns for both colors and weight the result - pi->value = evaluate_pawns(pos, wPawns, bPawns, pi) - - evaluate_pawns(pos, bPawns, wPawns, pi); + Key key = pos.pawn_key(); + Entry* e = pos.this_thread()->pawnsTable[key]; - pi->value = apply_weight(pi->value, PawnStructureWeight); + if (e->key == key) + return e; - return pi; + e->key = key; + e->score = evaluate(pos, e) - evaluate(pos, e); + e->asymmetry = popcount(e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK]); + e->openFiles = popcount(e->semiopenFiles[WHITE] & e->semiopenFiles[BLACK]); + return e; } -/// PawnInfoTable::evaluate_pawns() evaluates each pawn of the given color +/// Entry::shelter_storm() calculates shelter and storm penalties for the file +/// the king is on, as well as the two closest files. template -Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns, - Bitboard theirPawns, PawnInfo* pi) { +Value Entry::shelter_storm(const Position& pos, Square ksq) { const Color Them = (Us == WHITE ? BLACK : WHITE); - Bitboard b; - Square s; - File f; - Rank r; - bool passed, isolated, doubled, opposed, chain, backward, candidate; - Score value = SCORE_ZERO; - const Square* pl = pos.piece_list(Us, PAWN); + enum { BlockedByKing, Unopposed, BlockedByPawn, Unblocked }; - // Loop through all pawns of the current color and score each pawn - while ((s = *pl++) != SQ_NONE) + Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq)); + Bitboard ourPawns = b & pos.pieces(Us); + Bitboard theirPawns = b & pos.pieces(Them); + Value safety = MaxSafetyBonus; + File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq))); + + for (File f = center - File(1); f <= center + File(1); ++f) { - assert(pos.piece_on(s) == make_piece(Us, PAWN)); - - f = file_of(s); - r = rank_of(s); - - // This file cannot be half open - pi->halfOpenFiles[Us] &= ~(1 << f); - - // Our rank plus previous one. Used for chain detection - b = rank_bb(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1)); - - // Flag the pawn as passed, isolated, doubled or member of a pawn - // chain (but not the backward one). - passed = !(theirPawns & passed_pawn_mask(Us, s)); - doubled = ourPawns & squares_in_front_of(Us, s); - opposed = theirPawns & squares_in_front_of(Us, s); - isolated = !(ourPawns & adjacent_files_bb(f)); - chain = ourPawns & adjacent_files_bb(f) & b; - - // Test for backward pawn - backward = false; - - // If the pawn is passed, isolated, or member of a pawn chain it cannot - // be backward. If there are friendly pawns behind on adjacent files - // or if can capture an enemy pawn it cannot be backward either. - if ( !(passed | isolated | chain) - && !(ourPawns & attack_span_mask(Them, s)) - && !(pos.attacks_from(s, Us) & theirPawns)) - { - // We now know that there are no friendly pawns beside or behind this - // pawn on adjacent files. We now check whether the pawn is - // backward by looking in the forward direction on the adjacent - // files, and seeing whether we meet a friendly or an enemy pawn first. - b = pos.attacks_from(s, Us); - - // Note that we are sure to find something because pawn is not passed - // nor isolated, so loop is potentially infinite, but it isn't. - while (!(b & (ourPawns | theirPawns))) - Us == WHITE ? b <<= 8 : b >>= 8; - - // The friendly pawn needs to be at least two ranks closer than the - // enemy pawn in order to help the potentially backward pawn advance. - backward = (b | (Us == WHITE ? b << 8 : b >> 8)) & theirPawns; - } - - assert(opposed | passed | (attack_span_mask(Us, s) & theirPawns)); - - // A not passed pawn is a candidate to become passed if it is free to - // advance and if the number of friendly pawns beside or behind this - // pawn on adjacent files is higher or equal than the number of - // enemy pawns in the forward direction on the adjacent files. - candidate = !(opposed | passed | backward | isolated) - && (b = attack_span_mask(Them, s + pawn_push(Us)) & ourPawns) != 0 - && popcount(b) >= popcount(attack_span_mask(Us, s) & theirPawns); - - // Passed pawns will be properly scored in evaluation because we need - // full attack info to evaluate passed pawns. Only the frontmost passed - // pawn on each file is considered a true passed pawn. - if (passed && !doubled) - pi->passedPawns[Us] |= s; - - // Score this pawn - if (isolated) - value -= IsolatedPawnPenalty[opposed][f]; - - if (doubled) - value -= DoubledPawnPenalty[opposed][f]; - - if (backward) - value -= BackwardPawnPenalty[opposed][f]; - - if (chain) - value += ChainBonus[f]; - - if (candidate) - value += CandidateBonus[relative_rank(Us, s)]; + b = ourPawns & file_bb(f); + Rank rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1; + + b = theirPawns & file_bb(f); + Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1; + + safety -= ShelterWeakness[std::min(f, FILE_H - f)][rkUs] + + StormDanger + [f == file_of(ksq) && rkThem == relative_rank(Us, ksq) + 1 ? BlockedByKing : + rkUs == RANK_1 ? Unopposed : + rkThem == rkUs + 1 ? BlockedByPawn : Unblocked] + [std::min(f, FILE_H - f)][rkThem]; } - return value; -} -template -int computePawnShelter(const Position &pos, Square ksq) { - const Color Them = (Us == WHITE ? BLACK : WHITE); - const File kingFile = ShelterFile[file_of(ksq)]; - const Bitboard ourPawns = pos.pieces(PAWN, Us) & in_front_bb(Us, ksq); - const Bitboard theirPawns = pos.pieces(PAWN, Them) & (RankBB[rank_of(ksq)] | in_front_bb(Us, ksq)); - - int shelter = 0; - - // Compute king shelter and storm values for the file the king is on, as well as the two adjacent files. - for (int fileOffset = -1; fileOffset <= 1; fileOffset++) { - // Shelter takes full penalty for center file, otherwise it's half penalty - Bitboard shelterFile = ourPawns & FileBB[kingFile + fileOffset]; - Rank shelterClosest = shelterFile ? relative_rank(shelterFile) - : RANK_1; - - shelter += fileOffset == 0 ? PawnShelter[shelterClosest] - : score_non_center_file(PawnShelter[shelterClosest]); - - // Storm takes full penalty, unless there is an enemy pawn blocking us - Bitboard stormFile = theirPawns & FileBB[kingFile + fileOffset]; - Rank stormClosest = stormFile ? relative_rank(stormFile) - : RANK_1; - - shelter += shelterClosest + 1 == stormClosest ? PawnStorm[stormClosest] / 2 - : PawnStorm[stormClosest]; - } - - return shelter; + return safety; } -/// PawnInfo::updateShelter() calculates and caches king shelter. It is called -/// only when king square changes, about 20% of total king_shelter() calls. -template -Score PawnInfo::updateShelter(const Position& pos, Square ksq) { - int shelter = 0; - if (relative_rank(Us, ksq) <= RANK_4) - { - shelter = computePawnShelter(pos, ksq); - if (pos.can_castle(Us == WHITE ? WHITE_OO : BLACK_OO)) - shelter = std::min(shelter, computePawnShelter(pos, relative_square(Us, SQ_G1))); - if (pos.can_castle(Us == WHITE ? WHITE_OOO : BLACK_OOO)) - shelter = std::min(shelter, computePawnShelter(pos, relative_square(Us, SQ_C1))); - shelter = PawnShelterBasis - shelter; - } +/// Entry::do_king_safety() calculates a bonus for king safety. It is called only +/// when king square changes, which is about 20% of total king_safety() calls. + +template +Score Entry::do_king_safety(const Position& pos, Square ksq) { kingSquares[Us] = ksq; - kingShelters[Us] = make_score(shelter, 0); - return kingShelters[Us]; + castlingRights[Us] = pos.can_castle(Us); + int minKingPawnDistance = 0; + + Bitboard pawns = pos.pieces(Us, PAWN); + if (pawns) + while (!(DistanceRingBB[ksq][minKingPawnDistance++] & pawns)) {} + + Value bonus = shelter_storm(pos, ksq); + + // 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(MakeCastling::right)) + bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1))); + + return make_score(bonus, -16 * minKingPawnDistance); } // Explicit template instantiation -template Score PawnInfo::updateShelter(const Position& pos, Square ksq); -template Score PawnInfo::updateShelter(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, Square ksq); + +} // namespace Pawns