X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=5bf0e82ea98434aee57b171d5604b9ddf3055781;hp=135633a3ab9f74d8f1e6654983df16d781a92365;hb=4ae5a7b45a430aea5f4b21f9455b4db74ed1c44a;hpb=404c4122ce8f5dd55593668fc87ae46236a71b92 diff --git a/src/pawns.cpp b/src/pawns.cpp index 135633a3..45c40471 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) 2008-2013 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 @@ -21,262 +22,232 @@ #include #include "bitboard.h" -#include "bitcount.h" #include "pawns.h" #include "position.h" +#include "thread.h" namespace { #define V Value #define S(mg, eg) make_score(mg, eg) - // 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 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) + // Pawn penalties + constexpr Score Backward = S( 9, 24); + constexpr Score Doubled = S(11, 56); + constexpr Score Isolated = S( 5, 15); + constexpr Score WeakUnopposed = S( 13, 27); + constexpr Score Attacked2Unsupported = S( 0, 20); + + // 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 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) + // 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. + // [0][1-2] accommodate opponent pawn on edge (likely blocked by our king) + constexpr Value UnblockedStorm[int(FILE_NB) / 2][RANK_NB] = { + { V( 89), V(-285), V(-185), 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) } }; - // 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) } }; - - // 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) } }; - - // 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 #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); + constexpr Color Them = (Us == WHITE ? BLACK : WHITE); + constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH); - Bitboard b; + Bitboard b, neighbours, stoppers, doubled, support, phalanx; + Bitboard lever, leverPush; Square s; - File f; - Rank r; - bool passed, isolated, doubled, opposed, chain, backward, candidate; - Score value = SCORE_ZERO; - const Square* pl = pos.list(Us); + bool opposed, backward; + Score score = SCORE_ZERO; + const Square* pl = pos.squares(Us); - Bitboard ourPawns = pos.pieces(Us, PAWN); + Bitboard ourPawns = pos.pieces( Us, PAWN); Bitboard theirPawns = pos.pieces(Them, PAWN); - e->passedPawns[Us] = 0; + e->passedPawns[Us] = e->pawnAttacksSpan[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]; + e->pawnAttacks[Us] = pawn_attacks_bb(ourPawns); + + // Unsupported enemy pawns attacked twice by us + score += Attacked2Unsupported * popcount( theirPawns + & pawn_double_attacks_bb(ourPawns) + & ~pawn_attacks_bb(theirPawns)); // 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); + Rank r = relative_rank(Us, s); - // This file cannot be semi-open - e->semiopenFiles[Us] &= ~(1 << f); + e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s); - // 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 + 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(s); + phalanx = neighbours & rank_bb(s); + support = neighbours & rank_bb(s - Up); - // 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)); + // A pawn is backward when it is behind all pawns of the same color on + // the adjacent files and cannot safely advance. Phalanx and isolated + // pawns will be excluded when the pawn is scored. + backward = !(neighbours & forward_ranks_bb(Them, s)) + && (stoppers & (leverPush | (s + Up))); - // Test for backward pawn - backward = false; + // 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) || + (!(stoppers ^ leverPush) && popcount(phalanx) >= popcount(leverPush))) + e->passedPawns[Us] |= s; - // 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)) + else if (stoppers == square_bb(s + Up) && r >= RANK_5) { - // 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; + b = shift(support) & ~theirPawns; + while (b) + if (!more_than_one(theirPawns & PawnAttacks[Us][pop_lsb(&b)])) + e->passedPawns[Us] |= s; } - 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 (support | phalanx) + { + int v = Connected[r] * (phalanx ? 3 : 2) / (opposed ? 2 : 1) + + 17 * popcount(support); - if (doubled) - value -= Doubled[opposed][f]; + score += make_score(v, v * (r - 2) / 4); + } - if (backward) - value -= Backward[opposed][f]; + else if (!neighbours) + score -= Isolated + WeakUnopposed * int(!opposed); - if (chain) - value += ChainMember[f]; + else if (backward) + score -= Backward + WeakUnopposed * int(!opposed); - if (candidate) - value += CandidatePassed[relative_rank(Us, s)]; + if (doubled && !support) + score -= Doubled; } - return value; + return score; } } // namespace namespace Pawns { -/// 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. +/// 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. -Entry* probe(const Position& pos, Table& entries) { +Entry* probe(const Position& pos) { Key key = pos.pawn_key(); - Entry* e = entries[key]; + Entry* e = pos.this_thread()->pawnsTable[key]; if (e->key == key) return e; e->key = key; - e->value = evaluate(pos, e) - evaluate(pos, e); + e->scores[WHITE] = evaluate(pos, e); + e->scores[BLACK] = evaluate(pos, e); + return e; } -/// Entry::shelter_storm() calculates shelter and storm penalties for the file -/// the king is on, as well as the two adjacent files. +/// 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::shelter_storm(const Position& pos, Square ksq) { +void Entry::evaluate_shelter(const Position& pos, Square ksq, Score& shelter) { - const Color Them = (Us == WHITE ? BLACK : WHITE); + constexpr 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 b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq); + Bitboard ourPawns = b & pos.pieces(Us); Bitboard theirPawns = b & pos.pieces(Them); - Rank rkUs, rkThem; - File kf = file_of(ksq); - kf = (kf == FILE_A) ? FILE_B : (kf == FILE_H) ? FILE_G : kf; + Score bonus = make_score(5, 5); - for (int f = kf - 1; f <= kf + 1; f++) + File center = clamp(file_of(ksq), FILE_B, FILE_G); + for (File f = File(center - 1); f <= File(center + 1); ++f) { - // 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]; + b = ourPawns & file_bb(f); + Rank ourRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1; + + b = theirPawns & file_bb(f); + Rank theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1; + + int d = std::min(f, ~f); + bonus += make_score(ShelterStrength[d][ourRank], 0); + + if (ourRank && (ourRank == theirRank - 1)) + bonus -= make_score(82 * (theirRank == RANK_3), 82 * (theirRank == RANK_3)); + else + bonus -= make_score(UnblockedStorm[d][theirRank], 0); } - return safety; + if (mg_value(bonus) > mg_value(shelter)) + shelter = bonus; } -/// 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. +/// 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::update_safety(const Position& pos, Square ksq) { +Score Entry::do_king_safety(const Position& pos) { + Square ksq = pos.square(Us); kingSquares[Us] = ksq; - castleRights[Us] = pos.can_castle(Us); - minKPdistance[Us] = 0; + castlingRights[Us] = pos.castling_rights(Us); Bitboard pawns = pos.pieces(Us, PAWN); - if (pawns) - while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {} + int minPawnDist = pawns ? 8 : 0; + + if (pawns & PseudoAttacks[KING][ksq]) + minPawnDist = 1; - if (relative_rank(Us, ksq) > RANK_4) - return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]); + else while (pawns) + minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns))); - Value bonus = shelter_storm(pos, ksq); + Score shelter = make_score(-VALUE_INFINITE, VALUE_ZERO); + evaluate_shelter(pos, ksq, shelter); - // 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 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); - if (pos.can_castle(make_castle_right(Us, QUEEN_SIDE))) - bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1))); + if (pos.can_castle(Us | QUEEN_SIDE)) + evaluate_shelter(pos, relative_square(Us, SQ_C1), shelter); - return kingSafety[Us] = make_score(bonus, -16 * minKPdistance[Us]); + return shelter - make_score(VALUE_ZERO, 16 * minPawnDist); } // Explicit template instantiation -template Score Entry::update_safety(const Position& pos, Square ksq); -template Score Entry::update_safety(const Position& pos, Square ksq); +template Score Entry::do_king_safety(const Position& pos); +template Score Entry::do_king_safety(const Position& pos); } // namespace Pawns