X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fpawns.cpp;h=f71e2a3970f8cbd520e8567ec7d6729126b05eb8;hb=c8589903777b6e0289640b43fae966ded442af48;hp=17ca9d1e3228181a365cf203ea20e5f674645b9f;hpb=080a4995a3977a0fe7071e62151dc4d716a13302;p=stockfish diff --git a/src/pawns.cpp b/src/pawns.cpp index 17ca9d1e..c9c9e599 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) 2008-2009 Marco Costalba + Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2015-2019 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 @@ -17,389 +18,243 @@ along with this program. If not, see . */ - -//// -//// Includes -//// - #include -#include "bitcount.h" +#include "bitboard.h" #include "pawns.h" #include "position.h" +#include "thread.h" +namespace { -//// -//// Local definitions -//// + #define V Value + #define S(mg, eg) make_score(mg, eg) -namespace { + // Pawn penalties + constexpr Score Backward = S( 9, 24); + constexpr Score Doubled = S(11, 56); + constexpr Score Isolated = S( 5, 15); - /// Constants and variables + // Connected pawn bonus by opposed, phalanx, #support and rank + Score Connected[2][2][3][RANK_NB]; - // 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) + // Strength of pawn shelter for our king by [distance from edge][rank]. + // RANK_1 = 0 is used for files where we have no pawn, or pawn is behind our king. + constexpr Value ShelterStrength[int(FILE_NB) / 2][RANK_NB] = { + { V( -6), V( 81), V( 93), V( 58), V( 39), V( 18), V( 25) }, + { V(-43), V( 61), V( 35), V(-49), V(-29), V(-11), V( -63) }, + { V(-10), V( 75), V( 23), V( -2), V( 32), V( 3), V( -45) }, + { V(-39), V(-13), V(-29), V(-52), V(-48), V(-67), V(-166) } }; - // 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) + // Danger of enemy pawns moving toward our king by [distance from edge][rank]. + // RANK_1 = 0 is used for files where the enemy has no pawn, or their pawn + // is behind our king. + constexpr Value UnblockedStorm[int(FILE_NB) / 2][RANK_NB] = { + { V( 89), V(107), V(123), V(93), V(57), V( 45), V( 51) }, + { V( 44), V(-18), V(123), V(46), V(39), V( -7), V( 23) }, + { V( 4), V( 52), V(162), V(37), V( 7), V(-14), V( -2) }, + { V(-10), V(-14), V( 90), V(15), V( 2), V( -7), V(-16) } }; - // 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) - }; + #undef S + #undef V - // 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) - }; + template + Score evaluate(const Position& pos, Pawns::Entry* e) { - // 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) - }; + constexpr Color Them = (Us == WHITE ? BLACK : WHITE); + constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH); - // 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) - }; + Bitboard b, neighbours, stoppers, doubled, support, phalanx; + Bitboard lever, leverPush; + Square s; + bool opposed, backward; + Score score = SCORE_ZERO; + const Square* pl = pos.squares(Us); - // 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) - }; + Bitboard ourPawns = pos.pieces( Us, PAWN); + Bitboard theirPawns = pos.pieces(Them, PAWN); - // 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) - }; + e->passedPawns[Us] = e->pawnAttacksSpan[Us] = e->weakUnopposed[Us] = 0; + e->semiopenFiles[Us] = 0xFF; + e->kingSquares[Us] = SQ_NONE; + e->pawnAttacks[Us] = pawn_attacks_bb(ourPawns); + e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares); + e->pawnsOnSquares[Us][WHITE] = pos.count(Us) - e->pawnsOnSquares[Us][BLACK]; - // 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) - }; + // 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_file_bb(Us, s); + stoppers = theirPawns & passed_pawn_span(Us, s); + lever = theirPawns & PawnAttacks[Us][s]; + leverPush = theirPawns & PawnAttacks[Us][s + Up]; + doubled = ourPawns & (s - Up); + neighbours = ourPawns & adjacent_files_bb(f); + phalanx = neighbours & rank_bb(s); + support = neighbours & rank_bb(s - Up); + + // A pawn is backward when it is behind all pawns of the same color + // on the adjacent files and cannot be safely advanced. + backward = !(ourPawns & pawn_attack_span(Them, s + Up)) + && (stoppers & (leverPush | (s + Up))); + + // 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) + && (support || !more_than_one(lever)) + && popcount(phalanx) >= popcount(leverPush)) + e->passedPawns[Us] |= s; + + else if ( stoppers == square_bb(s + Up) + && relative_rank(Us, s) >= RANK_5) + { + b = shift(support) & ~theirPawns; + while (b) + if (!more_than_one(theirPawns & PawnAttacks[Us][pop_lsb(&b)])) + e->passedPawns[Us] |= s; + } - // 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) - }; + // Score this pawn + if (support | phalanx) + score += Connected[opposed][bool(phalanx)][popcount(support)][relative_rank(Us, s)]; - // 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 - }; + else if (!neighbours) + score -= Isolated, e->weakUnopposed[Us] += !opposed; - 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 - }; + else if (backward) + score -= Backward, e->weakUnopposed[Us] += !opposed; - // Pawn storm open file bonuses by file - const int16_t KStormOpenFileBonus[8] = { 31, 31, 18, 0, 0, 0, 0, 0 }; - const int16_t QStormOpenFileBonus[8] = { 0, 0, 0, 0, 0, 26, 42, 26 }; + if (doubled && !support) + score -= Doubled; + } - // Pawn storm lever bonuses by file - const int StormLeverBonus[8] = { -8, -8, -13, 0, 0, -13, -8, -8 }; + return score; + } -} +} // namespace +namespace Pawns { -//// -//// Functions -//// +/// 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. -/// Constructor +void init() { -PawnInfoTable::PawnInfoTable(unsigned numOfEntries) { + static constexpr int Seed[RANK_NB] = { 0, 13, 24, 18, 65, 100, 175, 330 }; - size = numOfEntries; - entries = new PawnInfo[size]; - if (entries == NULL) + for (int opposed = 0; opposed <= 1; ++opposed) + for (int phalanx = 0; phalanx <= 1; ++phalanx) + for (int support = 0; support <= 2; ++support) + for (Rank r = RANK_2; r < RANK_8; ++r) { - std::cerr << "Failed to allocate " << (numOfEntries * sizeof(PawnInfo)) - << " bytes for pawn hash table." << std::endl; - Application::exit_with_failure(); + int v = 17 * support; + v += (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed; + + Connected[opposed][phalanx][support][r] = make_score(v, v * (r - 2) / 4); } } -/// Destructor +/// 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. -PawnInfoTable::~PawnInfoTable() { - delete [] entries; -} +Entry* probe(const Position& pos) { + Key key = pos.pawn_key(); + Entry* e = pos.this_thread()->pawnsTable[key]; -/// 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. + if (e->key == key) + return e; -PawnInfo *PawnInfoTable::get_pawn_info(const Position &pos) { + e->key = key; + e->scores[WHITE] = evaluate(pos, e); + e->scores[BLACK] = evaluate(pos, e); + e->passedCount= popcount(e->passedPawns[WHITE] | e->passedPawns[BLACK]); + + return e; +} - assert(pos.is_ok()); - Key key = pos.get_pawn_key(); - int index = int(key & (size - 1)); - PawnInfo *pi = entries + index; +/// Entry::evaluate_shelter() calculates the shelter bonus and the storm +/// penalty for a king, looking at the king file and the two closest files. - // 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; +template +Value Entry::evaluate_shelter(const Position& pos, Square ksq) { - // Clear the PawnInfo object, and set the key - pi->clear(); - pi->key = key; + constexpr Color Them = (Us == WHITE ? BLACK : WHITE); + constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH); + constexpr Bitboard BlockRanks = (Us == WHITE ? Rank1BB | Rank2BB : Rank8BB | Rank7BB); - Value mgValue[2] = {Value(0), Value(0)}; - Value egValue[2] = {Value(0), Value(0)}; + Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq); + Bitboard ourPawns = b & pos.pieces(Us); + Bitboard theirPawns = b & pos.pieces(Them); - // Loop through the pawns for both colors - for (Color us = WHITE; us <= BLACK; us++) + Value safety = (shift(theirPawns) & (FileABB | FileHBB) & BlockRanks & ksq) ? + Value(374) : Value(5); + + File center = clamp(file_of(ksq), FILE_B, FILE_G); + for (File f = File(center - 1); f <= File(center + 1); ++f) { - Color them = opposite_color(us); - Bitboard ourPawns = pos.pawns(us); - Bitboard theirPawns = pos.pawns(them); - Bitboard pawns = ourPawns; - int bonus; - - // Initialize pawn storm scores by giving bonuses for open files - for (File f = FILE_A; f <= FILE_H; f++) - if (Position::file_is_half_open(ourPawns, f)) - { - pi->ksStormValue[us] += KStormOpenFileBonus[f]; - pi->qsStormValue[us] += QStormOpenFileBonus[f]; - } + b = ourPawns & file_bb(f); + Rank ourRank = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1; - // Loop through all pawns of the current color and score each pawn - while (pawns) - { - bool passed, doubled, isolated, backward, chain, candidate; - 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)); - - // The file containing the pawn is not half open - pi->halfOpenFiles[us] &= ~(1 << f); - - // Passed, isolated or doubled pawn? - passed = Position::pawn_is_passed(theirPawns, us, s); - isolated = Position::pawn_is_isolated(ourPawns, s); - 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 - 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; + b = theirPawns & file_bb(f); + Rank theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1; - // 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. - 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 - || (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; - if (us == WHITE) - { - for (b = pos.pawn_attacks(us, s); !(b & (ourPawns | theirPawns)); b <<= 8); - backward = (b | (b << 8)) & theirPawns; - } - else - { - for (b = pos.pawn_attacks(us, s); !(b & (ourPawns | theirPawns)); b >>= 8); - backward = (b | (b >> 8)) & theirPawns; - } - } + int d = std::min(f, ~f); + safety += ShelterStrength[d][ourRank]; + safety -= (ourRank && (ourRank == theirRank - 1)) ? 66 * (theirRank == RANK_3) + : UnblockedStorm[d][theirRank]; + } - // Test for candidate passed pawn - candidate = !passed - && Position::file_is_half_open(theirPawns, 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))) - { - // candidate = true; - passed = false; - } + return safety; +} - // Score this pawn - Value mv = Value(0), ev = Value(0); - if (isolated) - { - mv -= IsolatedPawnMidgamePenalty[f]; - ev -= IsolatedPawnEndgamePenalty[f]; - if (Position::file_is_half_open(theirPawns, f)) - { - mv -= IsolatedPawnMidgamePenalty[f] / 2; - ev -= IsolatedPawnEndgamePenalty[f] / 2; - } - } - if (doubled) - { - mv -= DoubledPawnMidgamePenalty[f]; - ev -= DoubledPawnEndgamePenalty[f]; - } - if (backward) - { - mv -= BackwardPawnMidgamePenalty[f]; - ev -= BackwardPawnEndgamePenalty[f]; - if (Position::file_is_half_open(theirPawns, f)) - { - mv -= BackwardPawnMidgamePenalty[f] / 2; - ev -= BackwardPawnEndgamePenalty[f] / 2; - } - } - if (chain) - { - mv += ChainMidgameBonus[f]; - ev += ChainEndgameBonus[f]; - } - if (candidate) - { - mv += CandidateMidgameBonus[relative_rank(us, s)]; - ev += CandidateEndgameBonus[relative_rank(us, s)]; - } - mgValue[us] += mv; - egValue[us] += ev; +/// 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. - // If the pawn is passed, set the square of the pawn in the passedPawns - // bitboard - if (passed) - set_bit(&(pi->passedPawns), s); - } // while(pawns) - } // for(colors) +template +Score Entry::do_king_safety(const Position& pos) { - pi->mgValue = int16_t(mgValue[WHITE] - mgValue[BLACK]); - pi->egValue = int16_t(egValue[WHITE] - egValue[BLACK]); - return pi; -} + Square ksq = pos.square(Us); + kingSquares[Us] = ksq; + castlingRights[Us] = pos.castling_rights(Us); + int minKingPawnDistance = 0; + Bitboard pawns = pos.pieces(Us, PAWN); + if (pawns) + while (!(DistanceRingBB[ksq][++minKingPawnDistance] & pawns)) {} -/// 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) { + Value bonus = evaluate_shelter(pos, ksq); - int shelter = 0; - Bitboard pawns = pos.pawns(c) & this_and_neighboring_files_bb(ksq); - unsigned r = ksq & (7 << 3); - for (int i = 1, k = (c ? -8 : 8); i < 4; i++) - { - r += k; - shelter += BitCount8Bit[(pawns >> r) & 0xFF] * (128 >> i); - } - kingSquares[c] = ksq; - kingShelters[c] = shelter; - return shelter; + // If we can castle use the bonus after the castling if it is bigger + if (pos.can_castle(Us | KING_SIDE)) + bonus = std::max(bonus, evaluate_shelter(pos, relative_square(Us, SQ_G1))); + + if (pos.can_castle(Us | QUEEN_SIDE)) + bonus = std::max(bonus, evaluate_shelter(pos, relative_square(Us, SQ_C1))); + + return make_score(bonus, -16 * minKingPawnDistance); } + +// Explicit template instantiation +template Score Entry::do_king_safety(const Position& pos); +template Score Entry::do_king_safety(const Position& pos); + +} // namespace Pawns