X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fpawns.cpp;h=c581c8e72e90fa7ef4ac64408b1fa56405b1d21b;hb=8df1cd10df0869f05916d1eb19e33b66127fcb86;hp=0089c42da28a818ec3ae0bca16331e2c1bb45c0d;hpb=d3600c39a745179ed6b094b305d0645e83a1ee86;p=stockfish diff --git a/src/pawns.cpp b/src/pawns.cpp index 0089c42d..c581c8e7 100644 --- a/src/pawns.cpp +++ b/src/pawns.cpp @@ -1,386 +1,262 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008 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 the Free Software Foundation, either version 3 of the License, or (at your option) any later version. - + Stockfish is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. - + You should have received a copy of the GNU General Public License along with this program. If not, see . */ - -//// -//// Includes -//// - +#include #include +#include "bitboard.h" #include "pawns.h" - - -//// -//// Local definitions -//// +#include "position.h" +#include "thread.h" namespace { - /// Constants and variables + #define V Value + #define S(mg, eg) make_score(mg, eg) - // Doubled pawn penalty by file, middle game. - const Value DoubledPawnMidgamePenalty[8] = { - Value(20), Value(30), Value(34), Value(34), - Value(34), Value(34), Value(30), Value(20) - }; + // Pawn penalties + constexpr Score Backward = S( 9, 24); + constexpr Score Doubled = S(11, 56); + constexpr Score Isolated = S( 5, 15); - // Doubled pawn penalty by file, endgame. - const Value DoubledPawnEndgamePenalty[8] = { - Value(35), Value(40), Value(40), Value(40), - Value(40), Value(40), Value(40), Value(35) - }; + // Connected pawn bonus by opposed, phalanx, #support and rank + Score Connected[2][2][3][RANK_NB]; - // Isolated pawn penalty by file, middle game. - const Value IsolatedPawnMidgamePenalty[8] = { - Value(20), Value(30), Value(34), Value(34), - Value(34), Value(34), Value(30), Value(20) + // 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) } }; - // Isolated pawn penalty by file, endgame. - const Value IsolatedPawnEndgamePenalty[8] = { - Value(35), Value(40), Value(40), Value(40), - Value(40), Value(40), Value(40), Value(35) + // 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) } }; - // Backward pawn penalty by file, middle game. - const Value BackwardPawnMidgamePenalty[8] = { - Value(16), Value(24), Value(27), Value(27), - Value(27), Value(27), Value(24), Value(16) - }; + #undef S + #undef V + + template + Score evaluate(const Position& pos, Pawns::Entry* e) { + + constexpr Color Them = (Us == WHITE ? BLACK : WHITE); + constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH); + + 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); + + Bitboard ourPawns = pos.pieces( Us, PAWN); + Bitboard theirPawns = pos.pieces(Them, PAWN); + + 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]; + + // 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_mask(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) + && popcount(support) >= popcount(lever) - 1 + && popcount(phalanx) >= popcount(leverPush)) + e->passedPawns[Us] |= s; + + else if ( stoppers == SquareBB[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; + } - // Backward pawn penalty by file, endgame. - const Value BackwardPawnEndgamePenalty[8] = { - Value(28), Value(32), Value(32), Value(32), - Value(32), Value(32), Value(32), Value(28) - }; + // Score this pawn + if (support | phalanx) + score += Connected[opposed][bool(phalanx)][popcount(support)][relative_rank(Us, s)]; - // Pawn chain membership bonus by file, middle game. - const Value ChainMidgameBonus[8] = { - Value(14), Value(16), Value(17), Value(18), - Value(18), Value(17), Value(16), Value(14) - }; + else if (!neighbours) + score -= Isolated, e->weakUnopposed[Us] += !opposed; - // Pawn chain membership bonus by file, endgame. - const Value ChainEndgameBonus[8] = { - Value(16), Value(16), Value(16), Value(16), - Value(16), Value(16), Value(16), Value(16) - }; - - // Candidate passed pawn bonus by rank, middle game. - const Value CandidateMidgameBonus[8] = { - Value(0), Value(12), Value(12), Value(20), - Value(40), Value(90), Value(0), Value(0) - }; + else if (backward) + score -= Backward, e->weakUnopposed[Us] += !opposed; - // Candidate passed pawn bonus by rank, endgame. - const Value CandidateEndgameBonus[8] = { - Value(0), Value(24), Value(24), Value(40), - Value(80), Value(180), Value(0), Value(0) - }; + if (doubled && !support) + score -= Doubled; + } - // Evaluate pawn storms? - const bool EvaluatePawnStorms = true; - - // Pawn storm tables for positions with opposite castling: - const int QStormTable[64] = { - 0, 0, 0, 0, 0, 0, 0, 0, - -22, -22, -22, -13, -4, 0, 0, 0, - -4, -9, -9, -9, -4, 0, 0, 0, - 9, 18, 22, 18, 9, 0, 0, 0, - 22, 31, 31, 22, 0, 0, 0, 0, - 31, 40, 40, 31, 0, 0, 0, 0, - 31, 40, 40, 31, 0, 0, 0, 0, - 0, 0, 0, 0, 0, 0, 0, 0 - }; - - const int KStormTable[64] = { - 0, 0, 0, 0, 0, 0, 0, 0, - 0, 0, 0, -4, -13, -22, -27, -27, - 0, 0, 0, -4, -9, -13, -18, -18, - 0, 0, 0, 0, 9, 9, 9, 9, - 0, 0, 0, 0, 9, 18, 27, 27, - 0, 0, 0, 0, 9, 27, 40, 36, - 0, 0, 0, 0, 0, 31, 40, 31, - 0, 0, 0, 0, 0, 0, 0, 0 - }; + return score; + } - // Pawn storm open file bonuses by file: - const int KStormOpenFileBonus[8] = { - 45, 45, 30, 0, 0, 0, 0, 0 - }; +} // namespace - const int QStormOpenFileBonus[8] = { - 0, 0, 0, 0, 0, 30, 45, 30 - }; +namespace Pawns { -} +/// 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. +void init() { -//// -//// Functions -//// + static constexpr int Seed[RANK_NB] = { 0, 13, 24, 18, 65, 100, 175, 330 }; -/// Constructor + 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) + { + int v = 17 * support; + v += (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed; -PawnInfoTable::PawnInfoTable(unsigned numOfEntries) { - size = numOfEntries; - entries = new PawnInfo[size]; - if(entries == NULL) { - std::cerr << "Failed to allocate " << (numOfEntries * sizeof(PawnInfo)) - << " bytes for pawn hash table." << std::endl; - exit(EXIT_FAILURE); + Connected[opposed][phalanx][support][r] = make_score(v, v * (r - 2) / 4); } - this->clear(); } -/// 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]; + if (e->key == key) + return e; -/// PawnInfoTable::clear() clears the pawn hash table by setting all -/// entries to 0. + e->key = key; + e->scores[WHITE] = evaluate(pos, e); + e->scores[BLACK] = evaluate(pos, e); + e->asymmetry = popcount( (e->passedPawns[WHITE] | e->passedPawns[BLACK]) + | (e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK])); -void PawnInfoTable::clear() { - memset(entries, 0, size * sizeof(PawnInfo)); + return e; } -/// 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. - -PawnInfo *PawnInfoTable::get_pawn_info(const Position &pos) { - assert(pos.is_ok()); - - Key key = pos.get_pawn_key(); - int index = int(key & (size - 1)); - PawnInfo *pi = entries + index; - - // 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: - pi->clear(); - pi->key = key; - - Value mgValue[2] = {Value(0), Value(0)}; - Value egValue[2] = {Value(0), Value(0)}; - - // Loop through the pawns for both colors: - for(Color us = WHITE; us <= BLACK; us++) { - Color them = opposite_color(us); - Bitboard ourPawns = pos.pawns(us); - Bitboard theirPawns = pos.pawns(them); - Bitboard pawns = ourPawns; - - // Initialize pawn storm scores by giving bonuses for open files: - if(EvaluatePawnStorms) - for(File f = FILE_A; f <= FILE_H; f++) - if(pos.file_is_half_open(us, f)) { - pi->ksStormValue[us] += KStormOpenFileBonus[f]; - pi->qsStormValue[us] += QStormOpenFileBonus[f]; - } +/// Entry::evaluate_shelter() calculates the shelter bonus and the storm +/// penalty for a king, looking at the king file and the two closest files. - // 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); - bool passed, doubled, isolated, backward, chain, candidate; - int bonus; - - assert(pos.piece_on(s) == pawn_of_color(us)); - - // The file containing the pawn is not half open: - pi->halfOpenFiles[us] &= ~(1 << f); - - // Passed, isolated or doubled pawn? - passed = pos.pawn_is_passed(us, s); - isolated = pos.pawn_is_isolated(us, s); - doubled = pos.pawn_is_doubled(us, s); - - if(EvaluatePawnStorms) { - // 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[]). This score is increased if - // there are enemy pawns on adjacent files in front of the pawn. - // This is because we want to be able to open files against the - // enemy king, and to avoid blocking the pawn structure (e.g. white - // pawns on h6, g5, black pawns on h7, g6, f7). - - // Kingside pawn storms: - bonus = KStormTable[relative_square(us, s)]; - if(bonus > 0 && outpost_mask(us, s) & theirPawns) { - switch(f) { - - case FILE_F: - bonus += bonus / 4; - break; - - case FILE_G: - bonus += bonus / 2 + bonus / 4; - break; - - case FILE_H: - bonus += bonus / 2; - break; - - default: - break; - } - } - pi->ksStormValue[us] += bonus; +template +Value Entry::evaluate_shelter(const Position& pos, Square ksq) { - // Queenside pawn storms: - bonus = QStormTable[relative_square(us, s)]; - if(bonus > 0 && passed_pawn_mask(us, s) & theirPawns) { - switch(f) { + constexpr Color Them = (Us == WHITE ? BLACK : WHITE); + constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH); + constexpr Bitboard BlockRanks = (Us == WHITE ? Rank1BB | Rank2BB : Rank8BB | Rank7BB); - case FILE_A: - bonus += bonus / 2; - break; + Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq); + Bitboard ourPawns = b & pos.pieces(Us); + Bitboard theirPawns = b & pos.pieces(Them); - case FILE_B: - bonus += bonus / 2 + bonus / 4; - break; + Value safety = (shift(theirPawns) & (FileABB | FileHBB) & BlockRanks & ksq) ? + Value(374) : Value(5); - case FILE_C: - bonus += bonus / 2; - break; + File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq))); + for (File f = File(center - 1); f <= File(center + 1); ++f) + { + b = ourPawns & file_bb(f); + Rank ourRank = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1; - default: - break; - } - } - pi->qsStormValue[us] += bonus; - } - - // Member of a pawn chain? 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 = (us == WHITE)? - (ourPawns & neighboring_files_bb(f) & (rank_bb(r) | rank_bb(r-1))) : - (ourPawns & neighboring_files_bb(f) & (rank_bb(r) | rank_bb(r+1))); - - - // Test for backward pawn. - - // If the pawn is isolated, passed, or member of a pawn chain, it cannot - // be backward: - if(passed || isolated || chain) - backward = false; - // If the pawn can capture an enemy pawn, it's not backward: - else if(pos.pawn_attacks(us, s) & theirPawns) - backward = false; - // Check for friendly pawns behind on neighboring files: - else if(ourPawns & in_front_bb(them, r) & neighboring_files_bb(f)) - backward = false; - else { - // We now know that there is 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; - } - } - - // Test for candidate passed pawn. - candidate = - (!passed && pos.file_is_half_open(them, f) && - count_1s_max_15(neighboring_files_bb(f) - & (in_front_bb(them, 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; - } - - // Score this pawn: - Value mv = Value(0), ev = Value(0); - if(isolated) { - mv -= IsolatedPawnMidgamePenalty[f]; - ev -= IsolatedPawnEndgamePenalty[f]; - if(pos.file_is_half_open(them, 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(pos.file_is_half_open(them, 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; - - // If the pawn is passed, set the square of the pawn in the passedPawns - // bitboard: - if(passed) - set_bit(&(pi->passedPawns), s); - } + b = theirPawns & file_bb(f); + Rank theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1; + + int d = std::min(f, ~f); + safety += ShelterStrength[d][ourRank]; + safety -= (ourRank && (ourRank == theirRank - 1)) ? 66 * (theirRank == RANK_3) + : UnblockedStorm[d][theirRank]; } - pi->mgValue = int16_t(mgValue[WHITE] - mgValue[BLACK]); - pi->egValue = int16_t(egValue[WHITE] - egValue[BLACK]); + return safety; +} + + +/// 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 Entry::do_king_safety(const Position& pos) { + + 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)) {} - return pi; + Value bonus = evaluate_shelter(pos, ksq); + + // 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