X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=135633a3ab9f74d8f1e6654983df16d781a92365;hp=0ab1c2622f14372b39baf9f82d99e744a0a9f97a;hb=404c4122ce8f5dd55593668fc87ae46236a71b92;hpb=7b721b3663920a2b74039ad6588ba4ed638c368b diff --git a/src/pawns.cpp b/src/pawns.cpp index 0ab1c262..135633a3 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) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2008-2013 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 @@ -17,330 +17,266 @@ along with this program. If not, see . */ - -//// -//// Includes -//// - +#include #include -#include +#include "bitboard.h" #include "bitcount.h" #include "pawns.h" #include "position.h" - -//// -//// Local definitions -//// - namespace { - /// Constants and variables - + #define V Value #define S(mg, eg) make_score(mg, eg) - // 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) - }; - - // 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) - }; - - // 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) - }; + // Doubled pawn penalty by opposed flag and file + const Score Doubled[2][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) }, + { 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 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) }}; + + // Backward pawn penalty by opposed flag and file + 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) }}; // Pawn chain membership bonus by file - const Score ChainBonus[8] = { + const Score ChainMember[FILE_NB] = { 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 - 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) }; - // Pawn storm tables for positions with opposite castling - const int QStormTable[64] = { - 0, 0, 0, 0, 0, 0, 0, 0, - -22,-22,-22,-14,-6, 0, 0, 0, - -6,-10,-10,-10,-6, 0, 0, 0, - 4, 12, 16, 12, 4, 0, 0, 0, - 16, 23, 23, 16, 0, 0, 0, 0, - 23, 31, 31, 23, 0, 0, 0, 0, - 23, 31, 31, 23, 0, 0, 0, 0, - 0, 0, 0, 0, 0, 0, 0, 0 - }; + // Weakness of our pawn shelter in front of the king indexed by [king pawn][rank] + const Value ShelterWeakness[2][RANK_NB] = + { { 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) } }; - const int KStormTable[64] = { - 0, 0, 0, 0, 0, 0, 0, 0, - 0, 0, 0,-10,-19,-28,-33,-33, - 0, 0, 0,-10,-15,-19,-24,-24, - 0, 0, 0, 0, 1, 1, 1, 1, - 0, 0, 0, 0, 1, 10, 19, 19, - 0, 0, 0, 0, 1, 19, 31, 27, - 0, 0, 0, 0, 0, 22, 31, 22, - 0, 0, 0, 0, 0, 0, 0, 0 - }; + // Danger of enemy pawns moving toward our king indexed by [pawn blocked][rank] + const Value StormDanger[2][RANK_NB] = + { { V(26), V(0), V(128), V(51), V(26) }, + { V(13), V(0), V( 64), V(25), V(13) } }; - // Pawn storm open file bonuses by file - const int16_t QStormOpenFileBonus[8] = { 31, 31, 18, 0, 0, 0, 0, 0 }; - const int16_t KStormOpenFileBonus[8] = { 0, 0, 0, 0, 0, 26, 42, 26 }; - - // Pawn storm lever bonuses by file - const int StormLeverBonus[8] = { -8, -8, -13, 0, 0, -13, -8, -8 }; + // 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. + const Value MaxSafetyBonus = V(263); #undef S -} - - -//// -//// Functions -//// - -/// PawnInfoTable c'tor and d'tor instantiated one each thread - -PawnInfoTable::PawnInfoTable() { - - entries = new PawnInfo[PawnTableSize]; - - if (!entries) - { - std::cerr << "Failed to allocate " << (PawnTableSize * sizeof(PawnInfo)) - << " bytes for pawn hash table." << std::endl; - Application::exit_with_failure(); + #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; + Square s; + File f; + Rank r; + bool passed, isolated, doubled, opposed, chain, 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] = 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 & BlackSquares); + 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); + r = rank_of(s); + + // This file cannot be semi-open + e->semiopenFiles[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 & forward_bb(Us, s); + opposed = theirPawns & forward_bb(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 & pawn_attack_span(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))) + b = shift_bb(b); + + // 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 | 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 or equal than 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[opposed][f]; + + if (backward) + value -= Backward[opposed][f]; + + if (chain) + value += ChainMember[f]; + + if (candidate) + value += CandidatePassed[relative_rank(Us, s)]; + } + + return value; } -} +} // namespace -PawnInfoTable::~PawnInfoTable() { +namespace Pawns { - delete [] entries; -} +/// 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. +Entry* probe(const Position& pos, Table& entries) { -/// PawnInfoTable::get_pawn_info() takes a position object as input, computes -/// a PawnInfo 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. + Key key = pos.pawn_key(); + Entry* e = entries[key]; -PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) const { + if (e->key == key) + return e; - assert(pos.is_ok()); - - Key key = pos.get_pawn_key(); - unsigned index = unsigned(key & (PawnTableSize - 1)); - PawnInfo* pi = entries + index; + e->key = key; + e->value = evaluate(pos, e) - evaluate(pos, e); + return e; +} - // 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; - // Clear the PawnInfo object, and set the key - memset(pi, 0, sizeof(PawnInfo)); - pi->kingSquares[WHITE] = pi->kingSquares[BLACK] = SQ_NONE; - pi->key = key; +/// Entry::shelter_storm() calculates shelter and storm penalties for the file +/// the king is on, as well as the two adjacent files. - // 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); +template +Value Entry::shelter_storm(const Position& pos, Square ksq) { - // Evaluate pawns for both colors - pi->value = evaluate_pawns(pos, whitePawns, blackPawns, pi) - - evaluate_pawns(pos, blackPawns, whitePawns, pi); - return pi; -} + const Color Them = (Us == WHITE ? BLACK : WHITE); + Value safety = MaxSafetyBonus; + Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq)); + Bitboard ourPawns = b & pos.pieces(Us) & ~rank_bb(ksq); + Bitboard theirPawns = b & pos.pieces(Them); + Rank rkUs, rkThem; + File kf = file_of(ksq); -/// PawnInfoTable::evaluate_pawns() evaluates each pawn of the given color + kf = (kf == FILE_A) ? FILE_B : (kf == FILE_H) ? FILE_G : kf; -template -Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns, - Bitboard theirPawns, PawnInfo* pi) const { - Bitboard b; - Square s; - File f; - Rank r; - int bonus; - bool passed, isolated, doubled, opposed, chain, backward, candidate; - Score value = SCORE_ZERO; - const Square* ptr = pos.piece_list_begin(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) + for (int f = kf - 1; f <= kf + 1; f++) { - f = square_file(s); - r = square_rank(s); - - assert(pos.piece_on(s) == piece_of_color_and_type(Us, PAWN)); - - // Calculate kingside and queenside pawn storm scores for both colors to be - // used when evaluating middle game positions with opposite side castling. - bonus = (f >= FILE_F ? evaluate_pawn_storm(s, r, f, theirPawns) : 0); - pi->ksStormValue[Us] += KStormTable[relative_square(Us, s)] + bonus; - - bonus = (f <= FILE_C ? evaluate_pawn_storm(s, r, f, theirPawns) : 0); - pi->qsStormValue[Us] += QStormTable[relative_square(Us, s)] + bonus; - - // Our rank plus previous one. Used for chain detection. - b = rank_bb(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1)); - - // Passed, isolated, doubled or member of a pawn - // chain (but not the backward one) ? - passed = !(theirPawns & passed_pawn_mask(Us, s)); - doubled = ourPawns & squares_behind(Us, s); - opposed = theirPawns & squares_in_front_of(Us, s); - isolated = !(ourPawns & neighboring_files_bb(f)); - chain = ourPawns & neighboring_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 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 & attack_span_mask(opposite_color(Us), s)) - && !(pos.attacks_from(s, Us) & theirPawns)) - { - // 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. - 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(passed | opposed | (attack_span_mask(Us, s) & theirPawns)); - - // Test for candidate passed pawn - candidate = !(opposed | passed) - && (b = attack_span_mask(opposite_color(Us), s + pawn_push(Us)) & ourPawns) != EmptyBoardBB - && count_1s_max_15(b) >= count_1s_max_15(attack_span_mask(Us, s) & theirPawns); - - // 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; - - // Mark the pawn as passed. Pawn will be properly scored in evaluation - // because we need full attack info to evaluate passed pawns. - if (passed) - set_bit(&(pi->passedPawns[Us]), s); - - // Score this pawn - if (isolated) - { - value -= IsolatedPawnPenalty[f]; - if (!opposed) - value -= IsolatedPawnPenalty[f] / 2; - } - if (doubled) - value -= DoubledPawnPenalty[f]; - - if (backward) - { - value -= BackwardPawnPenalty[f]; - if (!opposed) - value -= BackwardPawnPenalty[f] / 2; - } - if (chain) - value += ChainBonus[f]; - - if (candidate) - value += CandidateBonus[relative_rank(Us, s)]; + // Shelter penalty is higher for the pawn in front of the king + b = ourPawns & FileBB[f]; + rkUs = b ? rank_of(Us == WHITE ? lsb(b) : ~msb(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 ? lsb(b) : ~msb(b)) : RANK_1; + safety -= StormDanger[rkThem == rkUs + 1][rkThem]; } - return value; + return safety; } -/// PawnInfoTable::evaluate_pawn_storm() evaluates each pawn which seems -/// to have good chances of creating an open file by exchanging itself -/// against an enemy pawn on an adjacent file. +/// Entry::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. -template -int PawnInfoTable::evaluate_pawn_storm(Square s, Rank r, File f, Bitboard theirPawns) const { +template +Score Entry::update_safety(const Position& pos, Square ksq) { - const Bitboard StormFilesBB = (Side == KingSide ? FileFBB | FileGBB | FileHBB - : FileABB | FileBBB | FileCBB); - const int K = (Side == KingSide ? 2 : 4); - const File RookFile = (Side == KingSide ? FILE_H : FILE_A); + kingSquares[Us] = ksq; + castleRights[Us] = pos.can_castle(Us); + minKPdistance[Us] = 0; - Bitboard b = attack_span_mask(Us, s) & theirPawns & StormFilesBB; - int bonus = 0; + Bitboard pawns = pos.pieces(Us, PAWN); + if (pawns) + while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {} - while (b) - { - // Give a bonus according to the distance of the nearest enemy pawn - Square s2 = pop_1st_bit(&b); - Rank r2 = square_rank(s2); - int v = StormLeverBonus[f] - K * rank_distance(r, r2); + if (relative_rank(Us, ksq) > RANK_4) + return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]); - // 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) == RookFile ? 4 : 2); + Value bonus = shelter_storm(pos, ksq); - bonus += v; - } - return bonus; -} + // If we can castle use the bonus after the castle if is bigger + if (pos.can_castle(make_castle_right(Us, KING_SIDE))) + bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_G1))); + if (pos.can_castle(make_castle_right(Us, QUEEN_SIDE))) + bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1))); -/// PawnInfo::updateShelter calculates and caches king shelter. It is called -/// only when king square changes, about 20% of total king_shelter() calls. -Score PawnInfo::updateShelter(const Position& pos, Color c, Square ksq) { + return kingSafety[Us] = make_score(bonus, -16 * minKPdistance[Us]); +} - Bitboard pawns; - unsigned r, k, shelter = 0; +// Explicit template instantiation +template Score Entry::update_safety(const Position& pos, Square ksq); +template Score Entry::update_safety(const Position& pos, Square ksq); - if (relative_rank(c, ksq) <= RANK_4) - { - pawns = pos.pieces(PAWN, c) & this_and_neighboring_files_bb(ksq); - r = ksq & (7 << 3); - k = (c ? -8 : 8); - for (int i = 1; i < 4; i++) - { - r += k; - shelter += BitCount8Bit[(pawns >> r) & 0xFF] * (128 >> i); - } - } - kingSquares[c] = ksq; - kingShelters[c] = make_score(shelter, 0); - return kingShelters[c]; -} +} // namespace Pawns