X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=1e88652e154be205ee9a9008450f1ebc4bd53641;hp=f2e0c4c30fe4301b8c1e3fd64adea98f74154321;hb=c9dcda6ac488c0058ebd567e1f52e30b8cd0db20;hpb=304deb5e833baf47c147e93377f5c7ef582ab822 diff --git a/src/pawns.cpp b/src/pawns.cpp index f2e0c4c3..1e88652e 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) 2008-2012 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2008-2014 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 @@ -17,6 +17,7 @@ along with this program. If not, see . */ +#include #include #include "bitboard.h" @@ -29,253 +30,271 @@ 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) }}; + // Doubled pawn penalty by file + const Score Doubled[FILE_NB] = { + 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] = { + const Score Isolated[2][FILE_NB] = { { 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) }}; + 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] = { + const Score Backward[2][FILE_NB] = { { 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) }}; + 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) - }; + // Connected pawn bonus by file and rank (initialized by formula) + Score Connected[FILE_NB][RANK_NB]; // Candidate passed pawn bonus by rank - const Score CandidateBonus[8] = { + const Score CandidatePassed[RANK_NB] = { S( 0, 0), S( 6, 13), S(6,13), S(14,29), - S(34,68), S(83,166), S(0, 0), S( 0, 0) - }; + S(34,68), S(83,166), S(0, 0), S( 0, 0) }; - const Score PawnStructureWeight = S(233, 201); + // Bonus for file distance of the two outermost pawns + const Score PawnsFileSpan = S(0, 15); - // Weakness of our pawn shelter in front of the king indexed by [king pawn][rank] - const Value ShelterWeakness[2][8] = - { { V(141), V(0), V(38), V(102), V(128), V(141), V(141) }, - { V( 61), V(0), V(16), V( 44), V( 56), V( 61), V( 61) } }; + // Weakness of our pawn shelter in front of the king indexed by [rank] + const Value ShelterWeakness[RANK_NB] = + { V(100), V(0), V(27), V(73), V(92), V(101), V(101) }; - // Danger of enemy pawns moving toward our king indexed by [pawn blocked][rank] - const Value StormDanger[2][8] = - { { V(26), V(0), V(128), V(51), V(26) }, - { V(13), V(0), V( 64), V(25), V(13) } }; + // Danger of enemy pawns moving toward our king indexed by + // [no friendly pawn | pawn unblocked | pawn blocked][rank of enemy pawn] + const Value StormDanger[3][RANK_NB] = { + { V( 0), V(64), V(128), V(51), V(26) }, + { V(26), V(32), V( 96), V(38), V(20) }, + { V( 0), V( 0), V( 64), V(25), V(13) } }; // Max bonus for king safety. Corresponds to start position with all the pawns - // in front of the king and no enemy pawn on the horizont. + // in front of the king and no enemy pawn on the horizon. const Value MaxSafetyBonus = V(263); #undef S #undef V -} - - -/// PawnTable::probe() takes a position object as input, computes a PawnEntry -/// object, and returns a pointer to it. The result is also stored in a hash -/// table, so we don't have to recompute everything when the same pawn structure -/// occurs again. - -PawnEntry* PawnTable::probe(const Position& pos) const { - - Key key = pos.pawn_key(); - PawnEntry* pi = Base::probe(key); - - // 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; - 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; - - Bitboard wPawns = pos.pieces(PAWN, WHITE); - Bitboard bPawns = pos.pieces(PAWN, BLACK); - pi->pawnAttacks[WHITE] = ((wPawns & ~FileHBB) << 9) | ((wPawns & ~FileABB) << 7); - pi->pawnAttacks[BLACK] = ((bPawns & ~FileHBB) >> 7) | ((bPawns & ~FileABB) >> 9); - - pi->value = evaluate_pawns(pos, wPawns, bPawns, pi) - - evaluate_pawns(pos, bPawns, wPawns, pi); - - pi->value = apply_weight(pi->value, PawnStructureWeight); - - return pi; -} + template + Score evaluate(const Position& pos, Pawns::Entry* e) { + + const Color Them = (Us == WHITE ? BLACK : WHITE); + const Square Up = (Us == WHITE ? DELTA_N : DELTA_S); + const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW); + const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE); + + Bitboard b; + Square s; + File f; + bool passed, isolated, doubled, opposed, connected, backward, candidate; + Score value = SCORE_ZERO; + const Square* pl = pos.list(Us); + + Bitboard ourPawns = pos.pieces(Us, PAWN); + Bitboard theirPawns = pos.pieces(Them, PAWN); + + e->passedPawns[Us] = e->candidatePawns[Us] = 0; + e->kingSquares[Us] = SQ_NONE; + e->semiopenFiles[Us] = 0xFF; + e->pawnAttacks[Us] = shift_bb(ourPawns) | shift_bb(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)); + + f = file_of(s); + + // This file cannot be semi-open + e->semiopenFiles[Us] &= ~(1 << f); + + // Our rank plus previous one + b = rank_bb(s) | rank_bb(s - pawn_push(Us)); + + // Flag the pawn as passed, isolated, doubled or + // connected (but not the backward one). + connected = ourPawns & adjacent_files_bb(f) & b; + isolated = !(ourPawns & adjacent_files_bb(f)); + doubled = ourPawns & forward_bb(Us, s); + opposed = theirPawns & forward_bb(Us, s); + passed = !(theirPawns & passed_pawn_mask(Us, s)); + + // Test for backward pawn. + // If the pawn is passed, isolated, or connected it cannot be + // backward. If there are friendly pawns behind on adjacent files + // or if it can capture an enemy pawn it cannot be backward either. + if ( (passed | isolated | connected) + || (ourPawns & pawn_attack_span(Them, s)) + || (pos.attacks_from(s, Us) & theirPawns)) + backward = false; + else + { + // 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 picking the closest pawn there. + b = pawn_attack_span(Us, s) & (ourPawns | theirPawns); + b = pawn_attack_span(Us, s) & rank_bb(backmost_sq(Us, b)); + + // If we have an enemy pawn in the same or next rank, the pawn is + // backward because it cannot advance without being captured. + backward = (b | shift_bb(b)) & theirPawns; + } + + assert(opposed | passed | (pawn_attack_span(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 than or equal to the number of + // enemy pawns in the forward direction on the adjacent files. + candidate = !(opposed | passed | backward | isolated) + && (b = pawn_attack_span(Them, s + pawn_push(Us)) & ourPawns) != 0 + && popcount(b) >= popcount(pawn_attack_span(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) + e->passedPawns[Us] |= s; + + // Score this pawn + if (isolated) + value -= Isolated[opposed][f]; + + if (doubled) + value -= Doubled[f]; + + if (backward) + value -= Backward[opposed][f]; + + if (connected) + value += Connected[f][relative_rank(Us, s)]; + + if (candidate) + { + value += CandidatePassed[relative_rank(Us, s)]; + + if (!doubled) + e->candidatePawns[Us] |= s; + } + } + + // In endgame it's better to have pawns on both wings. So give a bonus according + // to file distance between left and right outermost pawns. + if (pos.count(Us) > 1) + { + b = e->semiopenFiles[Us] ^ 0xFF; + value += PawnsFileSpan * int(msb(b) - lsb(b)); + } + + return value; + } +} // namespace -/// PawnTable::evaluate_pawns() evaluates each pawn of the given color +namespace Pawns { -template -Score PawnTable::evaluate_pawns(const Position& pos, Bitboard ourPawns, - Bitboard theirPawns, PawnEntry* pi) { +/// init() initializes some tables by formula instead of hard-coding their values - const Color Them = (Us == WHITE ? BLACK : WHITE); +void init() { - 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); + const int bonusesByFile[8] = { 1, 3, 3, 4, 4, 3, 3, 1 }; + int bonus; - // 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)); - - 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). - chain = ourPawns & adjacent_files_bb(f) & b; - isolated = !(ourPawns & adjacent_files_bb(f)); - doubled = ourPawns & squares_in_front_of(Us, s); - opposed = theirPawns & squares_in_front_of(Us, s); - passed = !(theirPawns & passed_pawn_mask(Us, s)); - - // 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)) + for (Rank r = RANK_1; r < RANK_8; ++r) + for (File f = FILE_A; f <= FILE_H; ++f) { - // 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; + bonus = r * (r-1) * (r-2) + bonusesByFile[f] * (r/2 + 1); + Connected[f][r] = make_score(bonus, bonus); } +} - 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]; +/// probe() takes a position object as input, computes a Entry object, and returns +/// a pointer to it. The result is also stored in a hash table, so we don't have +/// to recompute everything when the same pawn structure occurs again. - if (backward) - value -= BackwardPawnPenalty[opposed][f]; +Entry* probe(const Position& pos, Table& entries) { - if (chain) - value += ChainBonus[f]; + Key key = pos.pawn_key(); + Entry* e = entries[key]; - if (candidate) - value += CandidateBonus[relative_rank(Us, s)]; - } + if (e->key == key) + return e; - return value; + e->key = key; + e->value = evaluate(pos, e) - evaluate(pos, e); + return e; } -/// PawnEntry::shelter_storm() calculates shelter and storm penalties for the file +/// Entry::shelter_storm() calculates shelter and storm penalties for the file /// the king is on, as well as the two adjacent files. template -Value PawnEntry::shelter_storm(const Position& pos, Square ksq) { +Value Entry::shelter_storm(const Position& pos, Square ksq) { const Color Them = (Us == WHITE ? BLACK : WHITE); Value safety = MaxSafetyBonus; - Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, ksq) | rank_bb(ksq)); - Bitboard ourPawns = b & pos.pieces(Us) & ~rank_bb(ksq); + 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); Rank rkUs, rkThem; - File kf = file_of(ksq); - - kf = (kf == FILE_A) ? kf++ : (kf == FILE_H) ? kf-- : kf; + File kf = std::max(FILE_B, std::min(FILE_G, file_of(ksq))); - for (int f = kf - 1; f <= kf + 1; f++) + for (File f = kf - File(1); f <= kf + File(1); ++f) { - // Shelter penalty is higher for the pawn in front of the king - b = ourPawns & FileBB[f]; - rkUs = b ? rank_of(Us == WHITE ? first_1(b) : ~last_1(b)) : RANK_1; - safety -= ShelterWeakness[f != kf][rkUs]; - - // Storm danger is smaller if enemy pawn is blocked - b = theirPawns & FileBB[f]; - rkThem = b ? rank_of(Us == WHITE ? first_1(b) : ~last_1(b)) : RANK_1; - safety -= StormDanger[rkThem == rkUs + 1][rkThem]; + b = ourPawns & file_bb(f); + rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1; + safety -= ShelterWeakness[rkUs]; + + b = theirPawns & file_bb(f); + rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1; + safety -= StormDanger[rkUs == RANK_1 ? 0 : rkThem == rkUs + 1 ? 2 : 1][rkThem]; } return safety; } -/// PawnEntry::update_safety() calculates and caches a bonus for king safety. It is -/// called only when king square changes, about 20% of total king_safety() calls. +/// Entry::update_safety() calculates and caches a bonus for king safety. +/// It is called only when king square changes, which is about 20% of total +/// king_safety() calls. template -Score PawnEntry::update_safety(const Position& pos, Square ksq) { +Score Entry::update_safety(const Position& pos, Square ksq) { kingSquares[Us] = ksq; + castlingFlags[Us] = pos.can_castle(Us); + minKPdistance[Us] = 0; + + Bitboard pawns = pos.pieces(Us, PAWN); + if (pawns) + while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {} if (relative_rank(Us, ksq) > RANK_4) - return kingSafety[Us] = SCORE_ZERO; + return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]); Value bonus = shelter_storm(pos, ksq); - // If we can castle use the bonus after the castle if is bigger - if (pos.can_castle(Us == WHITE ? WHITE_OO : BLACK_OO)) + // If we can castle use the bonus after the castling if it is bigger + if (pos.can_castle(make_castling_flag(Us, KING_SIDE))) bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_G1))); - if (pos.can_castle(Us == WHITE ? WHITE_OOO : BLACK_OOO)) + if (pos.can_castle(make_castling_flag(Us, QUEEN_SIDE))) bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1))); - return kingSafety[Us] = make_score(bonus, 0); + return kingSafety[Us] = make_score(bonus, -16 * minKPdistance[Us]); } // Explicit template instantiation -template Score PawnEntry::update_safety(const Position& pos, Square ksq); -template Score PawnEntry::update_safety(const Position& pos, Square ksq); +template Score Entry::update_safety(const Position& pos, Square ksq); +template Score Entry::update_safety(const Position& pos, Square ksq); + +} // namespace Pawns