X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=a5102db8aeb5b383c4ebe26b7ecf92462833a79f;hp=50eb3aa32c3871649cf242833b657ceec73ee497;hb=767b4f4fbe5ab2e63aceabd9005f4e1eb7cbcb51;hpb=667d24f22743959ceddda6af53718619ea5c551d diff --git a/src/pawns.cpp b/src/pawns.cpp index 50eb3aa3..a5102db8 100644 --- a/src/pawns.cpp +++ b/src/pawns.cpp @@ -1,8 +1,6 @@ /* Stockfish, a UCI chess playing engine derived from Glaurung 2.1 - Copyright (C) 2004-2008 Tord Romstad (Glaurung author) - Copyright (C) 2008-2015 Marco Costalba, Joona Kiiski, Tord Romstad - Copyright (C) 2015-2019 Marco Costalba, Joona Kiiski, Gary Linscott, Tord Romstad + Copyright (C) 2004-2020 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 @@ -32,15 +30,21 @@ namespace { #define S(mg, eg) make_score(mg, eg) // Pawn penalties - constexpr Score Backward = S( 9, 24); - constexpr Score BlockedStorm = S(82, 82); - constexpr Score Doubled = S(11, 56); - constexpr Score Isolated = S( 5, 15); - constexpr Score WeakLever = S( 0, 56); - constexpr Score WeakUnopposed = S(13, 27); + constexpr Score Backward = S( 8, 25); + constexpr Score Doubled = S(10, 55); + constexpr Score Isolated = S( 3, 15); + constexpr Score WeakLever = S( 3, 55); + constexpr Score WeakUnopposed = S(13, 25); + + // Bonus for blocked pawns at 5th or 6th rank + constexpr Score BlockedPawn[2] = { S(-13, -4), S(-5, 2) }; + + constexpr Score BlockedStorm[RANK_NB] = { + S(0, 0), S(0, 0), S(76, 78), S(-10, 15), S(-7, 10), S(-4, 6), S(-1, 2) + }; // Connected pawn bonus - constexpr int Connected[RANK_NB] = { 0, 7, 8, 12, 29, 48, 86 }; + 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. @@ -56,25 +60,31 @@ namespace { // 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( 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) } + { V( 85), V(-289), V(-166), V(97), V(50), V( 45), V( 50) }, + { V( 46), V( -25), V( 122), V(45), V(37), V(-10), V( 20) }, + { V( -6), V( 51), V( 168), V(34), V(-2), V(-22), V(-14) }, + { V(-15), V( -11), V( 101), V( 4), V(11), V(-15), V(-29) } }; #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(const Position& pos, Pawns::Entry* e) { - constexpr Color Them = (Us == WHITE ? BLACK : WHITE); - constexpr Direction Up = (Us == WHITE ? NORTH : SOUTH); + constexpr Color Them = ~Us; + constexpr Direction Up = pawn_push(Us); - Bitboard neighbours, stoppers, support, phalanx; - Bitboard lever, leverPush; + Bitboard neighbours, stoppers, support, phalanx, opposed; + Bitboard lever, leverPush, blocked; Square s; - bool opposed, backward, passed, doubled; + bool backward, passed, doubled; Score score = SCORE_ZERO; const Square* pl = pos.squares(Us); @@ -83,9 +93,10 @@ namespace { Bitboard doubleAttackThem = pawn_double_attacks_bb(theirPawns); - e->passedPawns[Us] = e->pawnAttacksSpan[Us] = 0; + e->passedPawns[Us] = 0; e->kingSquares[Us] = SQ_NONE; - e->pawnAttacks[Us] = pawn_attacks_bb(ourPawns); + e->pawnAttacks[Us] = e->pawnAttacksSpan[Us] = pawn_attacks_bb(ourPawns); + e->blockedCount += popcount(shift(ourPawns) & (theirPawns | doubleAttackThem)); // Loop through all pawns of the current color and score each pawn while ((s = *pl++) != SQ_NONE) @@ -94,34 +105,39 @@ namespace { Rank r = relative_rank(Us, s); - e->pawnAttacksSpan[Us] |= pawn_attack_span(Us, s); - // Flag the pawn opposed = theirPawns & forward_file_bb(Us, s); + blocked = theirPawns & (s + Up); stoppers = theirPawns & passed_pawn_span(Us, s); - lever = theirPawns & PawnAttacks[Us][s]; - leverPush = theirPawns & PawnAttacks[Us][s + Up]; + 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); // 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))); + // 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 == square_bb(s + Up) && r >= RANK_5 + || ( 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) @@ -130,21 +146,33 @@ namespace { // Score this pawn if (support | phalanx) { - int v = Connected[r] * (2 + bool(phalanx) - opposed) - + 21 * popcount(support); + int v = Connected[r] * (2 + bool(phalanx) - bool(opposed)) + + 22 * popcount(support); score += make_score(v, v * (r - 2) / 4); } else if (!neighbours) - score -= Isolated + WeakUnopposed * !opposed; + { + if ( opposed + && (ourPawns & forward_file_bb(Them, s)) + && !(theirPawns & adjacent_files_bb(s))) + score -= Doubled; + else + score -= Isolated + + WeakUnopposed * !opposed; + } else if (backward) - score -= Backward + WeakUnopposed * !opposed; + score -= Backward + + WeakUnopposed * !opposed; if (!support) - score -= Doubled * doubled - + WeakLever * more_than_one(lever); + score -= Doubled * doubled + + WeakLever * more_than_one(lever); + + if (blocked && r > RANK_4) + score += BlockedPawn[r-4]; } return score; @@ -154,6 +182,7 @@ namespace { namespace Pawns { + /// 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 @@ -168,6 +197,7 @@ Entry* probe(const Position& pos) { return e; e->key = key; + e->blockedCount = 0; e->scores[WHITE] = evaluate(pos, e); e->scores[BLACK] = evaluate(pos, e); @@ -179,17 +209,17 @@ Entry* probe(const Position& pos) { /// penalty for a king, looking at the king file and the two closest files. template -Score Entry::evaluate_shelter(const Position& pos, Square ksq) { +Score Entry::evaluate_shelter(const Position& pos, Square ksq) const { - constexpr Color Them = (Us == WHITE ? BLACK : WHITE); + constexpr Color Them = ~Us; Bitboard b = pos.pieces(PAWN) & ~forward_ranks_bb(Them, ksq); - Bitboard ourPawns = b & pos.pieces(Us); + Bitboard ourPawns = b & pos.pieces(Us) & ~pawnAttacks[Them]; Bitboard theirPawns = b & pos.pieces(Them); Score bonus = make_score(5, 5); - File center = clamp(file_of(ksq), FILE_B, FILE_G); + File center = std::clamp(file_of(ksq), FILE_B, FILE_G); for (File f = File(center - 1); f <= File(center + 1); ++f) { b = ourPawns & file_bb(f); @@ -198,11 +228,11 @@ Score Entry::evaluate_shelter(const Position& pos, Square ksq) { b = theirPawns & file_bb(f); int theirRank = b ? relative_rank(Us, frontmost_sq(Them, b)) : 0; - File d = map_to_queenside(f); + int d = edge_distance(f); bonus += make_score(ShelterStrength[d][ourRank], 0); if (ourRank && (ourRank == theirRank - 1)) - bonus -= BlockedStorm * int(theirRank == RANK_3); + bonus -= BlockedStorm[theirRank]; else bonus -= make_score(UnblockedStorm[d][theirRank], 0); } @@ -220,32 +250,28 @@ Score Entry::do_king_safety(const Position& pos) { Square ksq = pos.square(Us); kingSquares[Us] = ksq; castlingRights[Us] = pos.castling_rights(Us); + auto compare = [](Score a, Score b) { return mg_value(a) < mg_value(b); }; - Score shelters[3] = { evaluate_shelter(pos, ksq), - make_score(-VALUE_INFINITE, 0), - make_score(-VALUE_INFINITE, 0) }; + Score shelter = evaluate_shelter(pos, ksq); // If we can castle use the bonus after castling if it is bigger + if (pos.can_castle(Us & KING_SIDE)) - shelters[1] = evaluate_shelter(pos, relative_square(Us, SQ_G1)); + shelter = std::max(shelter, evaluate_shelter(pos, relative_square(Us, SQ_G1)), compare); if (pos.can_castle(Us & QUEEN_SIDE)) - shelters[2] = evaluate_shelter(pos, relative_square(Us, SQ_C1)); - - for (int i : {1, 2}) - if (mg_value(shelters[i]) > mg_value(shelters[0])) - shelters[0] = shelters[i]; + 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 = pawns ? 8 : 0; + int minPawnDist = 6; - if (pawns & PseudoAttacks[KING][ksq]) + if (pawns & attacks_bb(ksq)) minPawnDist = 1; else while (pawns) minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns))); - return shelters[0] - make_score(0, 16 * minPawnDist); + return shelter - make_score(0, 16 * minPawnDist); } // Explicit template instantiation