X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=c6d390b32efb0ea9e9a22276605a0c688485a0ae;hp=71b1738cc253f8b3b5bafc215d7d160ea71c8c01;hb=fc89dbcab2616603ba6edbf6277c3edecfc3a64a;hpb=9f28d8a854d05c6c6edcd6f8911b352477f82c91 diff --git a/src/pawns.cpp b/src/pawns.cpp index 71b1738c..c6d390b3 100644 --- a/src/pawns.cpp +++ b/src/pawns.cpp @@ -1,7 +1,7 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2009 Marco Costalba + Copyright (C) 2008-2010 Marco Costalba, Joona Kiiski, 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 @@ -38,65 +38,41 @@ namespace { /// Constants and variables - // Doubled pawn penalty by file, middle game - const Value DoubledPawnMidgamePenalty[8] = { - Value(13), Value(20), Value(23), Value(23), - Value(23), Value(23), Value(20), Value(13) - }; - - // Doubled pawn penalty by file, endgame - const Value DoubledPawnEndgamePenalty[8] = { - Value(43), Value(48), Value(48), Value(48), - Value(48), Value(48), Value(48), Value(43) - }; - - // Isolated pawn penalty by file, middle game - const Value IsolatedPawnMidgamePenalty[8] = { - Value(25), Value(36), Value(40), Value(40), - Value(40), Value(40), Value(36), Value(25) - }; - - // Isolated pawn penalty by file, endgame - const Value IsolatedPawnEndgamePenalty[8] = { - Value(30), Value(35), Value(35), Value(35), - Value(35), Value(35), Value(35), Value(30) - }; + #define S(mg, eg) make_score(mg, eg) - // Backward pawn penalty by file, middle game - const Value BackwardPawnMidgamePenalty[8] = { - Value(20), Value(29), Value(33), Value(33), - Value(33), Value(33), Value(29), Value(20) + // Doubled pawn penalty by file + const Score DoubledPawnPenalty[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) }; - // Backward pawn penalty by file, endgame - const Value BackwardPawnEndgamePenalty[8] = { - Value(28), Value(31), Value(31), Value(31), - Value(31), Value(31), Value(31), Value(28) + // Isolated pawn penalty by file + const Score IsolatedPawnPenalty[8] = { + S(25, 30), S(36, 35), S(40, 35), S(40, 35), + S(40, 35), S(40, 35), S(36, 35), S(25, 30) }; - // Pawn chain membership bonus by file, middle game - const Value ChainMidgameBonus[8] = { - Value(11), Value(13), Value(13), Value(14), - Value(14), Value(13), Value(13), Value(11) + // Backward pawn penalty by file + const Score BackwardPawnPenalty[8] = { + 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, endgame - const Value ChainEndgameBonus[8] = { - Value(-1), Value(-1), Value(-1), Value(-1), - Value(-1), Value(-1), Value(-1), Value(-1) + // 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) }; - // Candidate passed pawn bonus by rank, middle game - const Value CandidateMidgameBonus[8] = { - Value( 0), Value( 6), Value(6), Value(14), - Value(34), Value(83), Value(0), Value( 0) + // 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) }; - // Candidate passed pawn bonus by rank, endgame - const Value CandidateEndgameBonus[8] = { - Value( 0), Value( 13), Value(13), Value(29), - Value(68), Value(166), Value( 0), Value( 0) - }; + // UnpairedPawnsTable[] gives a score according to the number + // of panws that do not have an enemy pawn in front of them. + const int UnpairedPawnsTable[8] = { 32, 48, 64, 80, 96, 112, 128, 128 }; // Pawn storm tables for positions with opposite castling const int QStormTable[64] = { @@ -190,203 +166,193 @@ PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) { pi->clear(); pi->key = key; - Value mgValue[2] = {Value(0), Value(0)}; - Value egValue[2] = {Value(0), Value(0)}; + // Calculate pawn attacks + Bitboard whitePawns = pos.pieces(PAWN, WHITE); + Bitboard blackPawns = pos.pieces(PAWN, BLACK); + pi->pawnAttacks[WHITE] = ((whitePawns << 9) & ~FileABB) | ((whitePawns << 7) & ~FileHBB); + pi->pawnAttacks[BLACK] = ((blackPawns >> 7) & ~FileABB) | ((blackPawns >> 9) & ~FileHBB); - // Loop through the pawns for both colors - for (Color us = WHITE; us <= BLACK; us++) - { - Color them = opposite_color(us); - Bitboard ourPawns = pos.pieces(PAWN, us); - Bitboard theirPawns = pos.pieces(PAWN, them); - Bitboard pawns = ourPawns; - - // Initialize pawn storm scores by giving bonuses for open files - for (File f = FILE_A; f <= FILE_H; f++) - if (!(pawns & file_bb(f))) - { - pi->ksStormValue[us] += KStormOpenFileBonus[f]; - pi->qsStormValue[us] += QStormOpenFileBonus[f]; - pi->halfOpenFiles[us] |= (1 << f); - } - - // Loop through all pawns of the current color and score each pawn - while (pawns) - { - Square s = pop_1st_bit(&pawns); - File f = square_file(s); - Rank r = square_rank(s); - - assert(pos.piece_on(s) == piece_of_color_and_type(us, PAWN)); - - // Passed, isolated or doubled pawn? - bool passed = Position::pawn_is_passed(theirPawns, us, s); - bool isolated = Position::pawn_is_isolated(ourPawns, s); - bool doubled = Position::pawn_is_doubled(ourPawns, us, s); - - // We calculate kingside and queenside pawn storm - // scores for both colors. These are used when evaluating - // middle game positions with opposite side castling. - // - // Each pawn is given a base score given by a piece square table - // (KStormTable[] or QStormTable[]). Pawns which seem to have good - // chances of creating an open file by exchanging itself against an - // enemy pawn on an adjacent file gets an additional bonus. - - // Kingside pawn storms - int bonus = KStormTable[relative_square(us, s)]; - if (f >= FILE_F) - { - Bitboard b = outpost_mask(us, s) & theirPawns & (FileFBB | FileGBB | FileHBB); - while (b) - { - Square s2 = pop_1st_bit(&b); - if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2))) - { - // The enemy pawn has no pawn beside itself, which makes it - // particularly vulnerable. Big bonus, especially against a - // weakness on the rook file. - if (square_file(s2) == FILE_H) - bonus += 4*StormLeverBonus[f] - 8*square_distance(s, s2); - else - bonus += 2*StormLeverBonus[f] - 4*square_distance(s, s2); - } else - // There is at least one enemy pawn beside the enemy pawn we look - // at, which means that the pawn has somewhat better chances of - // defending itself by advancing. Smaller bonus. - bonus += StormLeverBonus[f] - 2*square_distance(s, s2); - } - } - pi->ksStormValue[us] += bonus; - - // Queenside pawn storms - bonus = QStormTable[relative_square(us, s)]; - if (f <= FILE_C) - { - Bitboard b = outpost_mask(us, s) & theirPawns & (FileABB | FileBBB | FileCBB); - while (b) - { - Square s2 = pop_1st_bit(&b); - if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2))) - { - // The enemy pawn has no pawn beside itself, which makes it - // particularly vulnerable. Big bonus, especially against a - // weakness on the rook file. - if (square_file(s2) == FILE_A) - bonus += 4*StormLeverBonus[f] - 16*square_distance(s, s2); - else - bonus += 2*StormLeverBonus[f] - 8*square_distance(s, s2); - } else - // There is at least one enemy pawn beside the enemy pawn we look - // at, which means that the pawn has somewhat better chances of - // defending itself by advancing. Smaller bonus. - bonus += StormLeverBonus[f] - 4*square_distance(s, s2); - } - } - pi->qsStormValue[us] += bonus; - - // Member of a pawn chain (but not the backward one)? We could speed up - // the test a little by introducing an array of masks indexed by color - // and square for doing the test, but because everything is hashed, - // it probably won't make any noticable difference. - bool chain = ourPawns - & neighboring_files_bb(f) - & (rank_bb(r) | rank_bb(r - (us == WHITE ? 1 : -1))); - - // Test for backward pawn - // - // If the pawn is passed, isolated, or member of a pawn chain - // it cannot be backward. If can capture an enemy pawn or if - // there are friendly pawns behind on neighboring files it cannot - // be backward either. - bool backward; - if ( passed - || isolated - || chain - || (pos.pawn_attacks(us, s) & theirPawns) - || (ourPawns & behind_bb(us, r) & neighboring_files_bb(f))) - backward = false; - else - { - // We now know that there are no friendly pawns beside or behind this - // pawn on neighboring files. We now check whether the pawn is - // backward by looking in the forward direction on the neighboring - // files, and seeing whether we meet a friendly or an enemy pawn first. - Bitboard b = pos.pawn_attacks(us, s); - if (us == WHITE) - { - for ( ; !(b & (ourPawns | theirPawns)); b <<= 8); - backward = (b | (b << 8)) & theirPawns; - } - else - { - for ( ; !(b & (ourPawns | theirPawns)); b >>= 8); - backward = (b | (b >> 8)) & theirPawns; - } - } - - // Test for candidate passed pawn - bool candidate; - candidate = !passed - && !(theirPawns & file_bb(f)) - && ( count_1s_max_15(neighboring_files_bb(f) & (behind_bb(us, r) | rank_bb(r)) & ourPawns) - - count_1s_max_15(neighboring_files_bb(f) & in_front_bb(us, r) & theirPawns) - >= 0); - - // In order to prevent doubled passed pawns from receiving a too big - // bonus, only the frontmost passed pawn on each file is considered as - // a true passed pawn. - if (passed && (ourPawns & squares_in_front_of(us, s))) - passed = false; - - // Score this pawn - if (passed) - set_bit(&(pi->passedPawns), s); - - if (isolated) - { - mgValue[us] -= IsolatedPawnMidgamePenalty[f]; - egValue[us] -= IsolatedPawnEndgamePenalty[f]; - if (!(theirPawns & file_bb(f))) - { - mgValue[us] -= IsolatedPawnMidgamePenalty[f] / 2; - egValue[us] -= IsolatedPawnEndgamePenalty[f] / 2; - } - } - if (doubled) - { - mgValue[us] -= DoubledPawnMidgamePenalty[f]; - egValue[us] -= DoubledPawnEndgamePenalty[f]; - } - if (backward) - { - mgValue[us] -= BackwardPawnMidgamePenalty[f]; - egValue[us] -= BackwardPawnEndgamePenalty[f]; - if (!(theirPawns & file_bb(f))) - { - mgValue[us] -= BackwardPawnMidgamePenalty[f] / 2; - egValue[us] -= BackwardPawnEndgamePenalty[f] / 2; - } - } - if (chain) - { - mgValue[us] += ChainMidgameBonus[f]; - egValue[us] += ChainEndgameBonus[f]; - } - if (candidate) - { - mgValue[us] += CandidateMidgameBonus[relative_rank(us, s)]; - egValue[us] += CandidateEndgameBonus[relative_rank(us, s)]; - } - } // while(pawns) - } // for(colors) - - pi->mgValue = int16_t(mgValue[WHITE] - mgValue[BLACK]); - pi->egValue = int16_t(egValue[WHITE] - egValue[BLACK]); + // Evaluate pawns for both colors + pi->value = evaluate_pawns(pos, whitePawns, blackPawns, pi) + - evaluate_pawns(pos, blackPawns, whitePawns, pi); return pi; } +/// PawnInfoTable::evaluate_pawns() evaluates each pawn of the given color + +template +Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns, + Bitboard theirPawns, PawnInfo* pi) { + Square s; + File f; + Rank r; + bool passed, isolated, doubled, opposed, chain, backward, candidate; + int bonus; + Score value = make_score(0, 0); + const Square* ptr = pos.piece_list_begin(Us, PAWN); + int unpairedPawnsNum = pos.piece_count(Us, PAWN); + + // Initialize pawn storm scores by giving bonuses for open files + for (f = FILE_A; f <= FILE_H; f++) + if (!(ourPawns & file_bb(f))) + { + pi->ksStormValue[Us] += KStormOpenFileBonus[f]; + pi->qsStormValue[Us] += QStormOpenFileBonus[f]; + pi->halfOpenFiles[Us] |= (1 << f); + } + + // Loop through all pawns of the current color and score each pawn + while ((s = *ptr++) != SQ_NONE) + { + f = square_file(s); + r = square_rank(s); + + assert(pos.piece_on(s) == piece_of_color_and_type(Us, PAWN)); + + // Passed, isolated or doubled pawn? + passed = !(theirPawns & passed_pawn_mask(Us, s)); + isolated = !(ourPawns & neighboring_files_bb(s)); + doubled = ourPawns & squares_behind(Us, s); + opposed = theirPawns & squares_in_front_of(Us, s); + + // Decrease number of unpaired pawns + if (opposed) + unpairedPawnsNum--; + + // We calculate kingside and queenside pawn storm + // scores for both colors. These are used when evaluating + // middle game positions with opposite side castling. + // + // Each pawn is given a base score given by a piece square table + // (KStormTable[] or QStormTable[]). Pawns which seem to have good + // chances of creating an open file by exchanging itself against an + // enemy pawn on an adjacent file gets an additional bonus. + + // Kingside pawn storms + bonus = KStormTable[relative_square(Us, s)]; + if (f >= FILE_F) + { + Bitboard b = outpost_mask(Us, s) & theirPawns & (FileFBB | FileGBB | FileHBB); + while (b) + { + // Give a bonus according to the distance of the nearest enemy pawn + Square s2 = pop_1st_bit(&b); + int v = StormLeverBonus[f] - 2 * square_distance(s, s2); + + // If enemy pawn has no pawn beside itself is particularly vulnerable. + // Big bonus, especially against a weakness on the rook file + if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2))) + v *= (square_file(s2) == FILE_H ? 4 : 2); + + bonus += v; + } + } + pi->ksStormValue[Us] += bonus; + + // Queenside pawn storms + bonus = QStormTable[relative_square(Us, s)]; + if (f <= FILE_C) + { + Bitboard b = outpost_mask(Us, s) & theirPawns & (FileABB | FileBBB | FileCBB); + while (b) + { + // Give a bonus according to the distance of the nearest enemy pawn + Square s2 = pop_1st_bit(&b); + int v = StormLeverBonus[f] - 4 * square_distance(s, s2); + + // If enemy pawn has no pawn beside itself is particularly vulnerable. + // Big bonus, especially against a weakness on the rook file + if (!(theirPawns & neighboring_files_bb(s2) & rank_bb(s2))) + v *= (square_file(s2) == FILE_A ? 4 : 2); + + bonus += v; + } + } + pi->qsStormValue[Us] += bonus; + + // Member of a pawn chain (but not the backward one)? We could speed up + // the test a little by introducing an array of masks indexed by color + // and square for doing the test, but because everything is hashed, + // it probably won't make any noticable difference. + chain = ourPawns + & neighboring_files_bb(f) + & (rank_bb(r) | rank_bb(r - (Us == WHITE ? 1 : -1))); + + // Test for backward pawn + // + // If the pawn is passed, isolated, or member of a pawn chain + // it cannot be backward. If can capture an enemy pawn or if + // there are friendly pawns behind on neighboring files it cannot + // be backward either. + if ( (passed | isolated | chain) + || (ourPawns & behind_bb(Us, r) & neighboring_files_bb(f)) + || (pos.attacks_from(s, Us) & theirPawns)) + backward = false; + else + { + // We now know that there are no friendly pawns beside or behind this + // pawn on neighboring files. We now check whether the pawn is + // backward by looking in the forward direction on the neighboring + // files, and seeing whether we meet a friendly or an enemy pawn first. + Bitboard 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; + } + + // Test for candidate passed pawn + candidate = !passed + && !opposed + && ( count_1s_max_15(neighboring_files_bb(f) & (behind_bb(Us, r) | rank_bb(r)) & ourPawns) + - count_1s_max_15(neighboring_files_bb(f) & in_front_bb(Us, r) & theirPawns) + >= 0); + + // In order to prevent doubled passed pawns from receiving a too big + // bonus, only the frontmost passed pawn on each file is considered as + // a true passed pawn. + if (passed && (ourPawns & squares_in_front_of(Us, s))) + passed = false; + + // Score this pawn + if (passed) + set_bit(&(pi->passedPawns), s); + + if (isolated) + { + value -= IsolatedPawnPenalty[f]; + if (!(theirPawns & file_bb(f))) + value -= IsolatedPawnPenalty[f] / 2; + } + if (doubled) + value -= DoubledPawnPenalty[f]; + + if (backward) + { + value -= BackwardPawnPenalty[f]; + if (!(theirPawns & file_bb(f))) + value -= BackwardPawnPenalty[f] / 2; + } + if (chain) + value += ChainBonus[f]; + + if (candidate) + value += CandidateBonus[relative_rank(Us, s)]; + } + + // Calculate a scale factor to be used to evaluate if position is drawish + pi->factor[Us] = UnpairedPawnsTable[unpairedPawnsNum]; + + return value; +} + + /// PawnInfo::updateShelter calculates and caches king shelter. It is called /// only when king square changes, about 20% of total get_king_shelter() calls. int PawnInfo::updateShelter(const Position& pos, Color c, Square ksq) {