X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fpawns.cpp;h=2906b0453b3c8508ddeb3ce129a00152d9a5b1cd;hb=f1088c98228ff5b992d6cdadfc678d36bf44f41b;hp=df7a0a2d3c507a1215b281b0a2ca6e4e4853c602;hpb=11207f7c1f943aa02bccbfa5eff6fdd18859721f;p=stockfish diff --git a/src/pawns.cpp b/src/pawns.cpp index df7a0a2d..212f0a28 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) 2008-2010 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad + Copyright (C) 2015-2018 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 @@ -17,343 +18,251 @@ along with this program. If not, see . */ - -//// -//// Includes -//// - +#include #include -#include -#include "bitcount.h" +#include "bitboard.h" #include "pawns.h" #include "position.h" - - -//// -//// Local definitions -//// +#include "thread.h" 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) + // Pawn penalties + constexpr Score Isolated = S( 5, 15); + constexpr Score Backward = S( 9, 24); + constexpr Score Doubled = S(11, 56); + + // Connected pawn bonus by opposed, phalanx, #support and rank + Score Connected[2][2][3][RANK_NB]; + + // 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( -3), V( 81), V( 93), V( 58), V( 39), V( 18), V( 25) }, + { V(-40), V( 61), V( 35), V(-49), V(-29), V(-11), V( -63) }, + { V( -7), V( 75), V( 23), V( -2), V( 32), V( 3), V( -45) }, + { V(-36), V(-13), V(-29), V(-52), V(-48), V(-67), V(-166) } }; - // 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) + // 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 - 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) - }; + // Danger of blocked enemy pawns storming our king, by rank + constexpr Value BlockedStorm[RANK_NB] = + { V(0), V(0), V(66), V(6), V(5), V(1), V(15) }; + + #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, supported, 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); + supported = 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(supported) >= 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(supported) & ~theirPawns; + while (b) + if (!more_than_one(theirPawns & PawnAttacks[Us][pop_lsb(&b)])) + e->passedPawns[Us] |= s; + } + + // Score this pawn + if (supported | phalanx) + score += Connected[opposed][bool(phalanx)][popcount(supported)][relative_rank(Us, s)]; + + else if (!neighbours) + score -= Isolated, e->weakUnopposed[Us] += !opposed; + + else if (backward) + score -= Backward, e->weakUnopposed[Us] += !opposed; + + if (doubled && !supported) + score -= Doubled; + } + + return score; + } - // 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) - }; +} // namespace - // 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) - }; +namespace Pawns { - // 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 - }; +/// 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. - 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 - }; +void init() { - // 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 }; + static constexpr int Seed[RANK_NB] = { 0, 13, 24, 18, 65, 100, 175, 330 }; - // Pawn storm lever bonuses by file - const int StormLeverBonus[8] = { -8, -8, -13, 0, 0, -13, -8, -8 }; + 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; + Connected[opposed][phalanx][support][r] = make_score(v, v * (r - 2) / 4); + } } -//// -//// Functions -//// - -/// Constructor +/// 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(unsigned numOfEntries) { +Entry* probe(const Position& pos) { - size = numOfEntries; - entries = new PawnInfo[size]; - if (!entries) - { - std::cerr << "Failed to allocate " << (numOfEntries * sizeof(PawnInfo)) - << " bytes for pawn hash table." << std::endl; - Application::exit_with_failure(); - } -} + Key key = pos.pawn_key(); + Entry* e = pos.this_thread()->pawnsTable[key]; + if (e->key == key) + return e; -/// Destructor + e->key = key; + e->scores[WHITE] = evaluate(pos, e); + e->scores[BLACK] = evaluate(pos, e); + e->openFiles = popcount(e->semiopenFiles[WHITE] & e->semiopenFiles[BLACK]); + e->asymmetry = popcount( (e->passedPawns[WHITE] | e->passedPawns[BLACK]) + | (e->semiopenFiles[WHITE] ^ e->semiopenFiles[BLACK])); -PawnInfoTable::~PawnInfoTable() { - delete [] entries; + return e; } -/// PawnInfo::clear() resets to zero the PawnInfo entry. Note that -/// kingSquares[] is initialized to SQ_NONE instead. - -void PawnInfo::clear() { - - memset(this, 0, sizeof(PawnInfo)); - kingSquares[WHITE] = kingSquares[BLACK] = SQ_NONE; -} +/// Entry::evaluate_shelter() calculates the shelter bonus and the storm +/// penalty for a king, looking at the king file and the two closest files. +template +Value Entry::evaluate_shelter(const Position& pos, Square ksq) { -/// 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. + constexpr Color Them = (Us == WHITE ? BLACK : WHITE); + constexpr Direction Down = (Us == WHITE ? SOUTH : NORTH); + constexpr Bitboard BlockRanks = (Us == WHITE ? Rank1BB | Rank2BB : Rank8BB | Rank7BB); -PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) { + Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq); + Bitboard ourPawns = b & pos.pieces(Us); + Bitboard theirPawns = b & pos.pieces(Them); - assert(pos.is_ok()); + Value safety = (ourPawns & file_bb(ksq)) ? Value(5) : Value(-5); - Key key = pos.get_pawn_key(); - int index = int(key & (size - 1)); - PawnInfo* pi = entries + index; + if (shift(theirPawns) & (FileABB | FileHBB) & BlockRanks & ksq) + safety += Value(374); - // 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; + 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); + int ourRank = b ? relative_rank(Us, backmost_sq(Us, b)) : 0; - // Clear the PawnInfo object, and set the key - pi->clear(); - pi->key = key; + b = theirPawns & file_bb(f); + int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0; - // 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); + int d = std::min(f, ~f); + safety += ShelterStrength[d][ourRank]; + safety -= (ourRank && (ourRank == theirRank - 1)) ? BlockedStorm[theirRank] + : UnblockedStorm[d][theirRank]; + } - // Evaluate pawns for both colors - pi->value = evaluate_pawns(pos, whitePawns, blackPawns, pi) - - evaluate_pawns(pos, blackPawns, whitePawns, pi); - return pi; + return safety; } -/// PawnInfoTable::evaluate_pawns() evaluates each pawn of the given color +/// 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 PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns, - Bitboard theirPawns, PawnInfo* pi) { - Square s; - File f; - Rank r; - bool passed, isolated, doubled, opposed, chain, backward, candidate; - int bonus; - Score value = make_score(0, 0); - 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) - { - f = square_file(s); - r = square_rank(s); - - assert(pos.piece_on(s) == piece_of_color_and_type(Us, PAWN)); - - // Passed, isolated or doubled pawn? - passed = !(theirPawns & passed_pawn_mask(Us, s)); - isolated = !(ourPawns & neighboring_files_bb(s)); - doubled = ourPawns & squares_behind(Us, s); - opposed = theirPawns & squares_in_front_of(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) - { - // Give a bonus according to the distance of the nearest enemy pawn - Square s2 = pop_1st_bit(&b); - int v = StormLeverBonus[f] - 2 * square_distance(s, s2); - - // 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) == FILE_H ? 4 : 2); - - bonus += v; - } - } - pi->ksStormValue[Us] += bonus; - - // 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) - { - // Give a bonus according to the distance of the nearest enemy pawn - Square s2 = pop_1st_bit(&b); - int v = StormLeverBonus[f] - 4 * square_distance(s, s2); - - // 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) == FILE_A ? 4 : 2); - - bonus += v; - } - } - 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) - || (ourPawns & behind_bb(Us, r) & neighboring_files_bb(f)) - || (pos.attacks_from(s, Us) & theirPawns)) - 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 = 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; - } - - // Test for candidate passed pawn - candidate = !passed - && !opposed - && ( 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))) - passed = false; - - // Score this pawn - if (passed) - set_bit(&(pi->passedPawns), s); - - if (isolated) - { - value -= IsolatedPawnPenalty[f]; - if (!(theirPawns & file_bb(f))) - value -= IsolatedPawnPenalty[f] / 2; - } - if (doubled) - value -= DoubledPawnPenalty[f]; - - if (backward) - { - value -= BackwardPawnPenalty[f]; - if (!(theirPawns & file_bb(f))) - value -= BackwardPawnPenalty[f] / 2; - } - if (chain) - value += ChainBonus[f]; - - if (candidate) - value += CandidateBonus[relative_rank(Us, s)]; - } +Score Entry::do_king_safety(const Position& pos, Square ksq) { - return value; -} + kingSquares[Us] = ksq; + castlingRights[Us] = pos.can_castle(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); - unsigned shelter = 0; - Bitboard pawns = pos.pieces(PAWN, 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(MakeCastling::right)) + bonus = std::max(bonus, evaluate_shelter(pos, relative_square(Us, SQ_G1))); + + if (pos.can_castle(MakeCastling::right)) + 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, Square ksq); +template Score Entry::do_king_safety(const Position& pos, Square ksq); + +} // namespace Pawns