X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fpawns.cpp;h=291d40b6858c8a1e193c42f7debceede349af125;hb=6ed81f09ffa513f0938c1a16fa4edd55e552c178;hp=1cdeb461d51e2a2e74a56860f3d3e3c65998d70d;hpb=1d4e7bbdf5a8b2e87daaa54eea52cbe01d699fdb;p=stockfish diff --git a/src/pawns.cpp b/src/pawns.cpp index 1cdeb461..291d40b6 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) 2015-2019 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 @@ -17,333 +18,232 @@ 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) - }; - - // 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) - }; - - // 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) + // Pawn penalties + constexpr Score Backward = S( 9, 24); + constexpr Score Doubled = S(11, 56); + constexpr Score Isolated = S( 5, 15); + + // Connected pawn bonus + constexpr int Connected[RANK_NB] = { 0, 7, 8, 12, 29, 48, 86 }; + + // 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) } }; - // 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) + // 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) } }; - // 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 - }; - - 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 - }; - - // 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 }; - #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->kingSquares[Us] = SQ_NONE; + e->pawnAttacks[Us] = pawn_attacks_bb(ourPawns); + + // 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); + Rank r = relative_rank(Us, s); + + 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) && r >= RANK_5) + { + b = shift(support) & ~theirPawns; + while (b) + if (!more_than_one(theirPawns & PawnAttacks[Us][pop_lsb(&b)])) + e->passedPawns[Us] |= s; + } + + // Score this pawn + if (support | phalanx) + { + int v = Connected[r] * (phalanx ? 3 : 2) / (opposed ? 2 : 1) + + 17 * popcount(support); + + score += make_score(v, v * (r - 2) / 4); + } + else if (!neighbours) + score -= Isolated, e->weakUnopposed[Us] += !opposed; + + else if (backward) + score -= Backward, e->weakUnopposed[Us] += !opposed; + + if (doubled && !support) + score -= Doubled; + } + + return score; + } +} // namespace -//// -//// Functions -//// +namespace Pawns { -/// PawnInfoTable c'tor and d'tor instantiated one each thread +/// 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) : size(numOfEntries) { +Entry* probe(const Position& pos) { - 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; -PawnInfoTable::~PawnInfoTable() { + e->key = key; + e->scores[WHITE] = evaluate(pos, e); + e->scores[BLACK] = evaluate(pos, e); - 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 +void Entry::evaluate_shelter(const Position& pos, Square ksq, Score& shelter) { -/// 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 BlockSquares = (Rank1BB | Rank2BB | Rank7BB | Rank8BB) + & (FileABB | FileHBB); -PawnInfo* PawnInfoTable::get_pawn_info(const Position& pos) const { + 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 bonus[] = { (shift(theirPawns) & BlockSquares & ksq) ? Value(374) : Value(5), + VALUE_ZERO }; - Key key = pos.get_pawn_key(); - unsigned index = unsigned(key & (size - 1)); - PawnInfo* pi = entries + index; + File center = clamp(file_of(ksq), FILE_B, FILE_G); + 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; - // 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; + b = theirPawns & file_bb(f); + Rank theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1; - // Clear the PawnInfo object, and set the key - pi->clear(); - pi->key = key; + int d = std::min(f, ~f); + bonus[MG] += ShelterStrength[d][ourRank]; - // 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); + if (ourRank && (ourRank == theirRank - 1)) + bonus[MG] -= 82 * (theirRank == RANK_3), bonus[EG] -= 82 * (theirRank == RANK_3); + else + bonus[MG] -= UnblockedStorm[d][theirRank]; + } - // Evaluate pawns for both colors - pi->value = evaluate_pawns(pos, whitePawns, blackPawns, pi) - - evaluate_pawns(pos, blackPawns, whitePawns, pi); - return pi; + if (bonus[MG] > mg_value(shelter)) + shelter = make_score(bonus[MG], bonus[EG]); } -/// 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) const { - Bitboard b; - Square s; - File f; - Rank r; - int bonus; - bool passed, isolated, doubled, opposed, chain, backward, candidate; - 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)); - - // 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(r + (Us == WHITE ? -1 : 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 - // - // 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)) - 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. - 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), s); - - // Score this pawn - 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) { - return value; -} + Square ksq = pos.square(Us); + kingSquares[Us] = ksq; + castlingRights[Us] = pos.castling_rights(Us); + Bitboard pawns = pos.pieces(Us, PAWN); + int minPawnDist = pawns ? 8 : 0; -/// 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. + if (pawns & PseudoAttacks[KING][ksq]) + minPawnDist = 1; -template -int PawnInfoTable::evaluate_pawn_storm(Square s, Rank r, File f, Bitboard theirPawns) const { + else while (pawns) + minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns))); - 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); + Score shelter = make_score(-VALUE_INFINITE, VALUE_ZERO); + evaluate_shelter(pos, ksq, shelter); - Bitboard b = attack_span_mask(Us, s) & theirPawns & StormFilesBB; - int bonus = 0; + // If we can castle use the bonus after the castling if it is bigger + if (pos.can_castle(Us | KING_SIDE)) + evaluate_shelter(pos, relative_square(Us, SQ_G1), shelter); - 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 (pos.can_castle(Us | QUEEN_SIDE)) + evaluate_shelter(pos, relative_square(Us, SQ_C1), shelter); - // 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); - - bonus += v; - } - return bonus; + return shelter - make_score(VALUE_ZERO, 16 * minPawnDist); } +// Explicit template instantiation +template Score Entry::do_king_safety(const Position& pos); +template Score Entry::do_king_safety(const Position& pos); -/// 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) { - - Bitboard pawns = pos.pieces(PAWN, c) & this_and_neighboring_files_bb(ksq); - unsigned shelter = 0; - 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; -} +} // namespace Pawns