X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=e582692e3251c38bd7df3cbf3404aa0a8c5841c3;hp=41d2e6f8148234d46d86a729c08a4468a737b597;hb=8a2c4134a650429488df48e1a02228cdb0fdf63d;hpb=10e64e05094e75d89baa4495fa867a8a64195bb7 diff --git a/src/pawns.cpp b/src/pawns.cpp index 41d2e6f8..e582692e 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) 2008-2015 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 @@ -17,275 +17,308 @@ 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) }}; + // 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 opposed, phalanx, twice supported and rank + Score Connected[2][2][2][RANK_NB]; + + // Levers bonus by rank + const Score Lever[RANK_NB] = { + S( 0, 0), S( 0, 0), S(0, 0), S(0, 0), + S(20,20), S(40,40), S(0, 0), S(0, 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) + // Unsupported pawn penalty + const Score UnsupportedPawnPenalty = S(20, 10); + + // Center bind bonus: Two pawns controlling the same central square + const Bitboard CenterBindMask[COLOR_NB] = { + (FileDBB | FileEBB) & (Rank5BB | Rank6BB | Rank7BB), + (FileDBB | FileEBB) & (Rank4BB | Rank3BB | Rank2BB) }; - const Score PawnStructureWeight = S(233, 201); + const Score CenterBind = S(16, 0); + + // Weakness of our pawn shelter in front of the king by [distance from edge][rank] + const Value ShelterWeakness[][RANK_NB] = { + { V( 99), V(20), V(26), V(54), V(85), V( 92), V(108) }, + { V(117), V( 1), V(27), V(71), V(94), V(104), V(118) }, + { V(104), V( 4), V(51), V(76), V(82), V(102), V( 97) }, + { V( 80), V(12), V(43), V(65), V(88), V( 91), V(115) } }; + + // Danger of enemy pawns moving toward our king by [type][distance from edge][rank] + const Value StormDanger[][4][RANK_NB] = { + { { V( 0), V( 65), V( 126), V(36), V(30) }, + { V( 0), V( 55), V( 135), V(36), V(23) }, + { V( 0), V( 47), V( 116), V(45), V(26) }, + { V( 0), V( 62), V( 127), V(57), V(34) } }, + { { V(21), V( 45), V( 93), V(50), V(19) }, + { V(23), V( 24), V( 105), V(41), V(13) }, + { V(23), V( 36), V( 101), V(38), V(20) }, + { V(30), V( 19), V( 110), V(41), V(27) } }, + { { V( 0), V( 0), V( 81), V(14), V( 4) }, + { V( 0), V( 0), V( 169), V(30), V( 3) }, + { V( 0), V( 0), V( 168), V(24), V( 5) }, + { V( 0), V( 0), V( 162), V(26), V(10) } }, + { { V( 0), V(-283), V(-298), V(57), V(29) }, + { V( 0), V( 63), V( 137), V(42), V(18) }, + { V( 0), V( 67), V( 145), V(49), V(33) }, + { V( 0), V( 62), V( 126), V(53), V(21) } } }; + + // 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 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, p, doubled, connected, supported; + Square s; + bool passed, isolated, opposed, phalanx, backward, lever; + Score score = SCORE_ZERO; + const Square* pl = pos.list(Us); + const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)]; + + Bitboard ourPawns = pos.pieces(Us , PAWN); + Bitboard theirPawns = pos.pieces(Them, PAWN); + + e->passedPawns[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)); + + File f = file_of(s); + + // This file cannot be semi-open + e->semiopenFiles[Us] &= ~(1 << f); + + // Previous rank + p = rank_bb(s - Up); + + // Flag the pawn + connected = ourPawns & adjacent_files_bb(f) & (rank_bb(s) | p); + phalanx = connected & rank_bb(s); + supported = connected & p; + 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)); + lever = theirPawns & pawnAttacksBB[s]; + + // Test for backward pawn. + // If the pawn is passed, isolated, connected or a lever it cannot be + // backward. If there are friendly pawns behind on adjacent files + // it cannot be backward either. + if ( (passed | isolated | lever | connected) + || (ourPawns & pawn_attack_span(Them, s))) + backward = false; + else + { + // We now know 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)); + + // 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) + score -= Isolated[opposed][f]; + + if (!supported && !isolated) + score -= UnsupportedPawnPenalty; + + if (doubled) + score -= Doubled[f] / distance(s, frontmost_sq(Us, doubled)); + + if (backward) + score -= Backward[opposed][f]; + + if (connected) + score += Connected[opposed][phalanx][more_than_one(supported)][relative_rank(Us, s)]; + + if (lever) + score += Lever[relative_rank(Us, s)]; + } + + b = e->semiopenFiles[Us] ^ 0xFF; + e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0; + + // Center binds: Two pawns controlling the same central square + b = shift_bb(ourPawns) & shift_bb(ourPawns) & CenterBindMask[Us]; + score += popcount(b) * CenterBind; + + return score; + } - typedef Value V; +} // namespace - // 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(141) }, - { V( 61), V(0), V(16), V( 44), V( 56), V( 61), V( 61), V( 61) } }; +namespace Pawns { - // 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(0), V(0), V(0) }, - { V(13), V(0), V( 64), V(25), V(13), V(0), V(0), V(0) } }; +/// 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. - // Max bonus for king safety. Corresponds to start position with all the pawns - // in front of the king and no enemy pawns on the horizont. - const Value MaxSafetyBonus = V(263); +void init() +{ + static const int Seed[RANK_NB] = { 0, 6, 15, 10, 57, 75, 135, 258 }; - 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); + 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(3 * v / 2, v); } } -/// 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. +/// 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. -PawnInfo* PawnInfoTable::pawn_info(const Position& pos) const { +Entry* probe(const Position& pos) { Key key = pos.pawn_key(); - PawnInfo* pi = 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; - - // 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; - - // 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* e = pos.this_thread()->pawnsTable[key]; - // Evaluate pawns for both colors and weight the result - pi->value = evaluate_pawns(pos, wPawns, bPawns, pi) - - evaluate_pawns(pos, bPawns, wPawns, pi); + if (e->key == key) + return e; - pi->value = apply_weight(pi->value, PawnStructureWeight); - - return pi; + e->key = key; + e->score = evaluate(pos, e) - evaluate(pos, e); + 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 adjacent 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); - - // 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). - 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)]; - } - return value; -} - - -template -int PawnInfo::shelter_storm(const Position& pos, Square ksq) { - - const Color Them = (Us == WHITE ? BLACK : WHITE); + enum { NoFriendlyPawn, Unblocked, BlockedByPawn, BlockedByKing }; - int safety = 0; - Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, ksq) | RankBB[rank_of(ksq)]); - Bitboard ourPawns = b & pos.pieces(Us) & ~RankBB[rank_of(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); + Value safety = MaxSafetyBonus; + File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq))); - // Compute shelter and storm values for the file the king is on, as well as - // the two adjacent files. Computation is done from the white point of view. - kf = (kf == FILE_A) ? kf++ : (kf == FILE_H) ? kf-- : kf; - - for (int f = kf - 1; f <= kf + 1; f++) + for (File f = center - File(1); f <= center + 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); + 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 ? NoFriendlyPawn : + rkThem == rkUs + 1 ? BlockedByPawn : Unblocked] + [std::min(f, FILE_H - f)][rkThem]; } return safety; } -/// PawnInfo::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::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 PawnInfo::update_safety(const Position& pos, Square ksq) { +Score Entry::do_king_safety(const Position& pos, Square ksq) { - int bonus = 0; + kingSquares[Us] = ksq; + castlingRights[Us] = pos.can_castle(Us); + minKingPawnDistance[Us] = 0; - if (relative_rank(Us, ksq) <= RANK_4) - { - bonus = shelter_storm(pos, ksq); + Bitboard pawns = pos.pieces(Us, PAWN); + if (pawns) + while (!(DistanceRingBB[ksq][minKingPawnDistance[Us]++] & pawns)) {} - // If we can castle use the bonus after the castle if is bigger - if (pos.can_castle(Us == WHITE ? WHITE_OO : BLACK_OO)) - bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_G1))); + if (relative_rank(Us, ksq) > RANK_4) + return make_score(0, -16 * minKingPawnDistance[Us]); - if (pos.can_castle(Us == WHITE ? WHITE_OOO : BLACK_OOO)) - bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1))); + Value bonus = shelter_storm(pos, ksq); - bonus += MaxSafetyBonus; // Offset to be sure bonus is always positive - } + // 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))); - kingSquares[Us] = ksq; - kingShelters[Us] = make_score(bonus, 0); - return kingShelters[Us]; + if (pos.can_castle(MakeCastling::right)) + bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1))); + + return make_score(bonus, -16 * minKingPawnDistance[Us]); } // Explicit template instantiation -template Score PawnInfo::update_safety(const Position& pos, Square ksq); -template Score PawnInfo::update_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, Square ksq); + +} // namespace Pawns