X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=src%2Fpawns.cpp;h=b26b1be656cda8a599ca2a00d8405fd45317ac9b;hb=77eeea407c9d10cf6dbca6f4e07efbbe836c4fb0;hp=861c421f172dcc80f8865322e208948d8c4d1a1b;hpb=1fd020a8ba98a95775639cdebd19e3592b767eb3;p=stockfish diff --git a/src/pawns.cpp b/src/pawns.cpp index 861c421f..5d6770ed 100644 --- a/src/pawns.cpp +++ b/src/pawns.cpp @@ -1,7 +1,6 @@ /* 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) 2004-2021 The Stockfish developers (see AUTHORS file) Stockfish is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by @@ -17,272 +16,285 @@ along with this program. If not, see . */ +#include #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( 6, 23); + constexpr Score Doubled = S(13, 53); + constexpr Score DoubledEarly = S(20, 10); + constexpr Score Isolated = S( 2, 15); + constexpr Score WeakLever = S( 5, 57); + constexpr Score WeakUnopposed = S(16, 22); + + // Bonus for blocked pawns at 5th or 6th rank + constexpr Score BlockedPawn[2] = { S(-15, -3), S(-6, 3) }; + + constexpr Score BlockedStorm[RANK_NB] = { + S(0, 0), S(0, 0), S(75, 78), S(-8, 16), S(-6, 10), S(-6, 6), S(0, 2) }; - // 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) + // Connected pawn bonus + constexpr int Connected[RANK_NB] = { 0, 5, 7, 11, 24, 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( -5), V( 82), V( 92), V( 54), V( 36), V( 22), V( 28) }, + { V(-44), V( 63), V( 33), V(-50), V(-30), V(-12), V( -62) }, + { V(-11), V( 77), V( 22), V( -6), V( 31), V( 8), V( -45) }, + { V(-39), V(-12), V(-29), V(-50), V(-43), V(-68), V(-164) } }; - // 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 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. Note that UnblockedStorm[0][1-2] accommodate opponent pawn + // on edge, likely blocked by our king. + constexpr Value UnblockedStorm[int(FILE_NB) / 2][RANK_NB] = { + { V( 87), V(-288), V(-168), V( 96), V( 47), V( 44), V( 46) }, + { V( 42), V( -25), V( 120), V( 45), V( 34), V( -9), V( 24) }, + { V( -8), V( 51), V( 167), V( 35), V( -4), V(-16), V(-12) }, + { V(-17), V( -13), V( 100), V( 4), V( 9), V(-16), V(-31) } + }; - // 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); + // KingOnFile[semi-open Us][semi-open Them] contains bonuses/penalties + // for king when the king is on a semi-open or open file. + constexpr Score KingOnFile[2][2] = {{ S(-21,10), S(-7, 1) }, + { S( 0,-3), S( 9,-4) }}; #undef S #undef V + + /// evaluate() calculates a score for the static pawn structure of the given position. + /// We cannot use the location of pieces or king in this function, as the evaluation + /// of the pawn structure will be stored in a small cache for speed reasons, and will + /// be re-used even when the pieces have moved. + template - Score evaluate_pawns(const Position& pos, Bitboard ourPawns, - Bitboard theirPawns, Pawns::Entry* e) { + Score evaluate(const Position& pos, Pawns::Entry* e) { - const Color Them = (Us == WHITE ? BLACK : WHITE); - const Square Up = (Us == WHITE ? DELTA_N : DELTA_S); + constexpr Color Them = ~Us; + constexpr Direction Up = pawn_push(Us); + constexpr Direction Down = -Up; - Bitboard b; + Bitboard neighbours, stoppers, support, phalanx, opposed; + Bitboard lever, leverPush, blocked; Square s; - File f; - Rank r; - bool passed, isolated, doubled, opposed, chain, backward, candidate; - Score value = SCORE_ZERO; - const Square* pl = pos.piece_list(Us, PAWN); + bool backward, passed, doubled; + Score score = SCORE_ZERO; + Bitboard b = pos.pieces(Us, PAWN); - // 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)); + Bitboard ourPawns = pos.pieces( Us, PAWN); + Bitboard theirPawns = pos.pieces(Them, PAWN); - f = file_of(s); - r = rank_of(s); + Bitboard doubleAttackThem = pawn_double_attacks_bb(theirPawns); - // This file cannot be semi-open - e->semiopenFiles[Us] &= ~(1 << f); + e->passedPawns[Us] = 0; + e->kingSquares[Us] = SQ_NONE; + e->pawnAttacks[Us] = e->pawnAttacksSpan[Us] = pawn_attacks_bb(ourPawns); + e->blockedCount += popcount(shift(ourPawns) & (theirPawns | doubleAttackThem)); - // Our rank plus previous one. Used for chain detection - b = rank_bb(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1)); + // Loop through all pawns of the current color and score each pawn + while (b) { + s = pop_lsb(&b); - // 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)); + assert(pos.piece_on(s) == make_piece(Us, PAWN)); + + Rank r = relative_rank(Us, s); - // Test for backward pawn - backward = false; + // Flag the pawn + opposed = theirPawns & forward_file_bb(Us, s); + blocked = theirPawns & (s + Up); + stoppers = theirPawns & passed_pawn_span(Us, s); + lever = theirPawns & pawn_attacks_bb(Us, s); + leverPush = theirPawns & pawn_attacks_bb(Us, s + Up); + doubled = ourPawns & (s - Up); + neighbours = ourPawns & adjacent_files_bb(s); + phalanx = neighbours & rank_bb(s); + support = neighbours & rank_bb(s - Up); - // 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 & attack_span_mask(Them, s)) - && !(pos.attacks_from(s, Us) & theirPawns)) + if (doubled) { - // 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))) - 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 | shift_bb(b)) & theirPawns; + // Additional doubled penalty if none of their pawns is fixed + if (!(ourPawns & shift(theirPawns | pawn_attacks_bb(theirPawns)))) + score -= DoubledEarly; } - assert(opposed | passed | (attack_span_mask(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 = attack_span_mask(Them, s + pawn_push(Us)) & ourPawns) != 0 - && popcount(b) >= popcount(attack_span_mask(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) + // A pawn is backward when it is behind all pawns of the same color on + // the adjacent files and cannot safely advance. + backward = !(neighbours & forward_ranks_bb(Them, s + Up)) + && (leverPush | blocked); + + // Compute additional span if pawn is not backward nor blocked + if (!backward && !blocked) + e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s); + + // A pawn is passed if one of the three following conditions is true: + // (a) there is no stoppers except some levers + // (b) the only stoppers are the leverPush, but we outnumber them + // (c) there is only one front stopper which can be levered. + // (Refined in Evaluation::passed) + passed = !(stoppers ^ lever) + || ( !(stoppers ^ leverPush) + && popcount(phalanx) >= popcount(leverPush)) + || ( stoppers == blocked && r >= RANK_5 + && (shift(support) & ~(theirPawns | doubleAttackThem))); + + passed &= !(forward_file_bb(Us, s) & ourPawns); + + // Passed pawns will be properly scored later in evaluation when we have + // full attack info. + if (passed) e->passedPawns[Us] |= s; // Score this pawn - if (isolated) - value -= Isolated[opposed][f]; - - if (doubled) - value -= Doubled[opposed][f]; + if (support | phalanx) + { + int v = Connected[r] * (2 + bool(phalanx) - bool(opposed)) + + 22 * popcount(support); - if (backward) - value -= Backward[opposed][f]; + score += make_score(v, v * (r - 2) / 4); + } - if (chain) - value += ChainMember[f]; + else if (!neighbours) + { + if ( opposed + && (ourPawns & forward_file_bb(Them, s)) + && !(theirPawns & adjacent_files_bb(s))) + score -= Doubled; + else + score -= Isolated + + WeakUnopposed * !opposed; + } - if (candidate) - value += CandidatePassed[relative_rank(Us, s)]; - } + else if (backward) + score -= Backward + + WeakUnopposed * !opposed * bool(~(FileABB | FileHBB) & s); - e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & BlackSquares); - e->pawnsOnSquares[Us][WHITE] = pos.piece_count(Us, PAWN) - e->pawnsOnSquares[Us][BLACK]; + if (!support) + score -= Doubled * doubled + + WeakLever * more_than_one(lever); - e->pawnsOnSquares[Them][BLACK] = popcount(theirPawns & BlackSquares); - e->pawnsOnSquares[Them][WHITE] = pos.piece_count(Them, PAWN) - e->pawnsOnSquares[Them][BLACK]; + if (blocked && r >= RANK_5) + score += BlockedPawn[r - RANK_5]; + } - 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. -Entry* probe(const Position& pos, Table& entries) { +/// 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) { Key key = pos.pawn_key(); - Entry* e = entries[key]; + Entry* e = pos.this_thread()->pawnsTable[key]; - // If e->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 (e->key == key) return e; e->key = key; - e->passedPawns[WHITE] = e->passedPawns[BLACK] = 0; - e->kingSquares[WHITE] = e->kingSquares[BLACK] = SQ_NONE; - e->semiopenFiles[WHITE] = e->semiopenFiles[BLACK] = 0xFF; + e->blockedCount = 0; + e->scores[WHITE] = evaluate(pos, e); + e->scores[BLACK] = evaluate(pos, e); - Bitboard wPawns = pos.pieces(WHITE, PAWN); - Bitboard bPawns = pos.pieces(BLACK, PAWN); - e->pawnAttacks[WHITE] = shift_bb(wPawns) | shift_bb(wPawns); - e->pawnAttacks[BLACK] = shift_bb(bPawns) | shift_bb(bPawns); - - e->value = evaluate_pawns(pos, wPawns, bPawns, e) - - evaluate_pawns(pos, bPawns, wPawns, 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) { +Score Entry::evaluate_shelter(const Position& pos, Square ksq) const { - const Color Them = (Us == WHITE ? BLACK : WHITE); + constexpr Color Them = ~Us; - Value safety = MaxSafetyBonus; - Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, 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) & ~pawnAttacks[Them]; 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 = std::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); + int ourRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0; + + b = theirPawns & file_bb(f); + int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0; + + int d = edge_distance(f); + bonus += make_score(ShelterStrength[d][ourRank], 0); + + if (ourRank && (ourRank == theirRank - 1)) + bonus -= BlockedStorm[theirRank]; + else + bonus -= make_score(UnblockedStorm[d][theirRank], 0); } - return safety; + // King On File + bonus -= KingOnFile[pos.is_on_semiopen_file(Us, ksq)][pos.is_on_semiopen_file(Them, ksq)]; + + return 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); + auto compare = [](Score a, Score b) { return mg_value(a) < mg_value(b); }; - Bitboard pawns = pos.pieces(Us, PAWN); - if (pawns) - while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {} + Score shelter = evaluate_shelter(pos, ksq); - if (relative_rank(Us, ksq) > RANK_4) - return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]); + // If we can castle use the bonus after castling if it is bigger - Value bonus = shelter_storm(pos, ksq); + if (pos.can_castle(Us & KING_SIDE)) + shelter = std::max(shelter, evaluate_shelter(pos, relative_square(Us, SQ_G1)), compare); - // 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 (pos.can_castle(Us & QUEEN_SIDE)) + shelter = std::max(shelter, evaluate_shelter(pos, relative_square(Us, SQ_C1)), compare); + + // In endgame we like to bring our king near our closest pawn + Bitboard pawns = pos.pieces(Us, PAWN); + int minPawnDist = 6; - if (pos.can_castle(make_castle_right(Us, QUEEN_SIDE))) - bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1))); + if (pawns & attacks_bb(ksq)) + minPawnDist = 1; + else while (pawns) + minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns))); - return kingSafety[Us] = make_score(bonus, -16 * minKPdistance[Us]); + return shelter - make_score(0, 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