X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=915cd0ce22771aab12bf45e2a43e35bbcb8a4743;hp=e582692e3251c38bd7df3cbf3404aa0a8c5841c3;hb=353e20674b2019094059caaa3567e9a44abe9cd1;hpb=8a2c4134a650429488df48e1a02228cdb0fdf63d diff --git a/src/pawns.cpp b/src/pawns.cpp index e582692e..7b266e77 100644 --- a/src/pawns.cpp +++ b/src/pawns.cpp @@ -2,6 +2,7 @@ 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) 2015-2020 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 @@ -21,7 +22,6 @@ #include #include "bitboard.h" -#include "bitcount.h" #include "pawns.h" #include "position.h" #include "thread.h" @@ -31,73 +31,36 @@ namespace { #define V Value #define S(mg, eg) make_score(mg, eg) - // Doubled pawn penalty by file - const Score Doubled[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) }; - - // 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) } }; - - // Connected pawn bonus by opposed, phalanx, twice supported and rank - Score Connected[2][2][2][RANK_NB]; - - // Levers bonus by rank - const Score Lever[RANK_NB] = { - S( 0, 0), S( 0, 0), S(0, 0), S(0, 0), - S(20,20), S(40,40), S(0, 0), S(0, 0) }; - - // Unsupported pawn penalty - const Score UnsupportedPawnPenalty = S(20, 10); - - // Center bind bonus: Two pawns controlling the same central square - const Bitboard CenterBindMask[COLOR_NB] = { - (FileDBB | FileEBB) & (Rank5BB | Rank6BB | Rank7BB), - (FileDBB | FileEBB) & (Rank4BB | Rank3BB | Rank2BB) + // 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); + + // 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) } }; - const Score CenterBind = S(16, 0); - - // Weakness of our pawn shelter in front of the king by [distance from edge][rank] - const Value ShelterWeakness[][RANK_NB] = { - { V( 99), V(20), V(26), V(54), V(85), V( 92), V(108) }, - { V(117), V( 1), V(27), V(71), V(94), V(104), V(118) }, - { V(104), V( 4), V(51), V(76), V(82), V(102), V( 97) }, - { V( 80), V(12), V(43), V(65), V(88), V( 91), V(115) } }; - - // Danger of enemy pawns moving toward our king by [type][distance from edge][rank] - const Value StormDanger[][4][RANK_NB] = { - { { V( 0), V( 65), V( 126), V(36), V(30) }, - { V( 0), V( 55), V( 135), V(36), V(23) }, - { V( 0), V( 47), V( 116), V(45), V(26) }, - { V( 0), V( 62), V( 127), V(57), V(34) } }, - { { V(21), V( 45), V( 93), V(50), V(19) }, - { V(23), V( 24), V( 105), V(41), V(13) }, - { V(23), V( 36), V( 101), V(38), V(20) }, - { V(30), V( 19), V( 110), V(41), V(27) } }, - { { V( 0), V( 0), V( 81), V(14), V( 4) }, - { V( 0), V( 0), V( 169), V(30), V( 3) }, - { V( 0), V( 0), V( 168), V(24), V( 5) }, - { V( 0), V( 0), V( 162), V(26), V(10) } }, - { { V( 0), V(-283), V(-298), V(57), V(29) }, - { V( 0), V( 63), V( 137), V(42), V(18) }, - { V( 0), V( 67), V( 145), V(49), V(33) }, - { V( 0), V( 62), V( 126), V(53), V(21) } } }; - - // Max bonus for king safety. Corresponds to start position with all the pawns - // in front of the king and no enemy pawn on the horizon. - const Value MaxSafetyBonus = V(258); + // 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( 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 @@ -105,107 +68,94 @@ namespace { 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; + constexpr Direction Up = pawn_push(Us); - Bitboard b, p, doubled, connected, supported; + Bitboard neighbours, stoppers, support, phalanx, opposed; + Bitboard lever, leverPush, blocked; Square s; - bool passed, isolated, opposed, phalanx, backward, lever; + bool backward, passed, doubled; Score score = SCORE_ZERO; - const Square* pl = pos.list(Us); - const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)]; + const Square* pl = pos.squares(Us); - Bitboard ourPawns = pos.pieces(Us , PAWN); + Bitboard ourPawns = pos.pieces( Us, PAWN); Bitboard theirPawns = pos.pieces(Them, PAWN); + Bitboard doubleAttackThem = pawn_double_attacks_bb(theirPawns); + e->passedPawns[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 & DarkSquares); - e->pawnsOnSquares[Us][WHITE] = pos.count(Us) - e->pawnsOnSquares[Us][BLACK]; + e->pawnAttacks[Us] = e->pawnAttacksSpan[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); - - // This file cannot be semi-open - e->semiopenFiles[Us] &= ~(1 << f); - - // Previous rank - p = rank_bb(s - Up); + Rank r = relative_rank(Us, s); // Flag the pawn - connected = ourPawns & adjacent_files_bb(f) & (rank_bb(s) | p); - phalanx = connected & rank_bb(s); - supported = connected & p; - 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)); - lever = theirPawns & pawnAttacksBB[s]; - - // Test for backward pawn. - // If the pawn is passed, isolated, connected or a lever it cannot be - // backward. If there are friendly pawns behind on adjacent files - // it cannot be backward either. - if ( (passed | isolated | lever | connected) - || (ourPawns & pawn_attack_span(Them, s))) - backward = false; - else - { - // We now know 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 picking the closest pawn there. - b = pawn_attack_span(Us, s) & (ourPawns | theirPawns); - b = pawn_attack_span(Us, s) & rank_bb(backmost_sq(Us, b)); - - // If we have an enemy pawn in the same or next rank, the pawn is - // backward because it cannot advance without being captured. - backward = (b | shift_bb(b)) & theirPawns; - } - - assert(opposed | passed | (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) + 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]; + doubled = ourPawns & (s - Up); + neighbours = ourPawns & adjacent_files_bb(s); + phalanx = neighbours & rank_bb(s); + support = neighbours & rank_bb(s - Up); + + e->blockedCount += blocked || more_than_one(leverPush); + + // 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) - score -= Isolated[opposed][f]; - - if (!supported && !isolated) - score -= UnsupportedPawnPenalty; + if (support | phalanx) + { + int v = Connected[r] * (4 + 2 * bool(phalanx) - 2 * bool(opposed) - bool(blocked)) / 2 + + 21 * popcount(support); - if (doubled) - score -= Doubled[f] / distance(s, frontmost_sq(Us, doubled)); + score += make_score(v, v * (r - 2) / 4); + } - if (backward) - score -= Backward[opposed][f]; + else if (!neighbours) + score -= Isolated + + WeakUnopposed * !opposed; - if (connected) - score += Connected[opposed][phalanx][more_than_one(supported)][relative_rank(Us, s)]; + else if (backward) + score -= Backward + + WeakUnopposed * !opposed; - if (lever) - score += Lever[relative_rank(Us, s)]; + if (!support) + score -= Doubled * doubled + + WeakLever * more_than_one(lever); } - b = e->semiopenFiles[Us] ^ 0xFF; - e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0; - - // Center binds: Two pawns controlling the same central square - b = shift_bb(ourPawns) & shift_bb(ourPawns) & CenterBindMask[Us]; - score += popcount(b) * CenterBind; - return score; } @@ -213,26 +163,6 @@ namespace { namespace Pawns { -/// 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. - -void init() -{ - static const int Seed[RANK_NB] = { 0, 6, 15, 10, 57, 75, 135, 258 }; - - for (int opposed = 0; opposed <= 1; ++opposed) - for (int phalanx = 0; phalanx <= 1; ++phalanx) - for (int apex = 0; apex <= 1; ++apex) - for (Rank r = RANK_2; r < RANK_8; ++r) - { - int v = (Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0)) >> opposed; - v += (apex ? v / 2 : 0); - Connected[opposed][phalanx][apex][r] = make_score(3 * v / 2, v); - } -} - - /// 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 @@ -247,44 +177,47 @@ Entry* probe(const Position& pos) { return e; e->key = key; - e->score = evaluate(pos, e) - evaluate(pos, e); + e->blockedCount = 0; + 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) { +Score Entry::evaluate_shelter(const Position& pos, Square ksq) { - const Color Them = (Us == WHITE ? BLACK : WHITE); + constexpr Color Them = ~Us; - enum { NoFriendlyPawn, Unblocked, BlockedByPawn, BlockedByKing }; - - Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | 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); - Value safety = MaxSafetyBonus; - File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq))); - for (File f = center - File(1); f <= center + File(1); ++f) + Score bonus = make_score(5, 5); + + File center = Utility::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 rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1; + 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; - b = theirPawns & file_bb(f); - Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1; + File d = File(edge_distance(f)); + bonus += make_score(ShelterStrength[d][ourRank], 0); - safety -= ShelterWeakness[std::min(f, FILE_H - f)][rkUs] - + StormDanger - [f == file_of(ksq) && rkThem == relative_rank(Us, ksq) + 1 ? BlockedByKing : - rkUs == RANK_1 ? NoFriendlyPawn : - rkThem == rkUs + 1 ? BlockedByPawn : Unblocked] - [std::min(f, FILE_H - f)][rkThem]; + if (ourRank && (ourRank == theirRank - 1)) + bonus -= BlockedStorm * int(theirRank == RANK_3); + else + bonus -= make_score(UnblockedStorm[d][theirRank], 0); } - return safety; + return bonus; } @@ -292,33 +225,37 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) { /// when king square changes, which is about 20% of total king_safety() calls. template -Score Entry::do_king_safety(const Position& pos, Square ksq) { +Score Entry::do_king_safety(const Position& pos) { + Square ksq = pos.square(Us); kingSquares[Us] = ksq; - castlingRights[Us] = pos.can_castle(Us); - minKingPawnDistance[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 (!(DistanceRingBB[ksq][minKingPawnDistance[Us]++] & pawns)) {} + Score shelter = evaluate_shelter(pos, ksq); + + // If we can castle use the bonus after castling if it is bigger - if (relative_rank(Us, ksq) > RANK_4) - return make_score(0, -16 * minKingPawnDistance[Us]); + if (pos.can_castle(Us & KING_SIDE)) + shelter = std::max(shelter, evaluate_shelter(pos, relative_square(Us, SQ_G1)), compare); - Value bonus = shelter_storm(pos, ksq); + if (pos.can_castle(Us & QUEEN_SIDE)) + shelter = std::max(shelter, evaluate_shelter(pos, relative_square(Us, SQ_C1)), compare); - // If we can castle use the bonus after the castling if it is bigger - if (pos.can_castle(MakeCastling::right)) - bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_G1))); + // 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(MakeCastling::right)) - bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1))); + if (pawns & PseudoAttacks[KING][ksq]) + minPawnDist = 1; + else while (pawns) + minPawnDist = std::min(minPawnDist, distance(ksq, pop_lsb(&pawns))); - return make_score(bonus, -16 * minKingPawnDistance[Us]); + return shelter - make_score(0, 16 * minPawnDist); } // 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); +template Score Entry::do_king_safety(const Position& pos); +template Score Entry::do_king_safety(const Position& pos); } // namespace Pawns