X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=b26b1be656cda8a599ca2a00d8405fd45317ac9b;hp=d65b0418f0145f448c3d37dff8ecb7262c86fdaf;hb=296534f23489e6d95ba7ce1bb35e8a2cbf9a5a9d;hpb=457ac26de5e2925c87bdc0169478d138074c50f8 diff --git a/src/pawns.cpp b/src/pawns.cpp index d65b0418..b26b1be6 100644 --- a/src/pawns.cpp +++ b/src/pawns.cpp @@ -1,7 +1,7 @@ /* 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) 2008-2014 Marco Costalba, Joona Kiiski, 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 @@ -30,53 +30,65 @@ 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) }}; + // 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) }}; + 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) - }; - - // 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) - }; - - // Weakness of our pawn shelter in front of the king indexed by [rank] - const Value ShelterWeakness[RANK_NB] = - { V(100), V(0), V(27), V(73), V(92), V(101), V(101) }; - - // Danger of enemy pawns moving toward our king indexed by - // [no friendly pawn | pawn unblocked | pawn blocked][rank of enemy pawn] - const Value StormDanger[3][RANK_NB] = { - { V( 0), V(64), V(128), V(51), V(26) }, - { V(26), V(32), V( 96), V(38), V(20) }, - { V( 0), V( 0), V( 64), V(25), V(13) }}; + S(33, 31), S(33, 31), S(29, 31), S(20, 28) } }; + + // Connected pawn bonus by opposed, phalanx flags and rank + Score Connected[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); + + // Weakness of our pawn shelter in front of the king by [distance from edge][rank] + const Value ShelterWeakness[][RANK_NB] = { + { V(101), V(10), V(24), V(68), V(90), V( 95), V(102) }, + { V(105), V( 1), V(30), V(76), V(95), V(100), V(105) }, + { V( 99), V( 0), V(32), V(72), V(92), V(101), V(100) }, + { V( 94), V( 1), V(31), V(68), V(89), V( 98), V(106) } }; + + // Danger of enemy pawns moving toward our king by [type][distance from edge][rank] + const Value StormDanger[][4][RANK_NB] = { + { { V( 0), V( 61), V( 128), V(47), V(27) }, + { V( 0), V( 66), V( 131), V(49), V(27) }, + { V( 0), V( 62), V( 126), V(52), V(23) }, + { V( 0), V( 63), V( 128), V(52), V(26) } }, + { { V(25), V( 33), V( 95), V(39), V(21) }, + { V(24), V( 33), V( 97), V(42), V(22) }, + { V(24), V( 33), V( 93), V(35), V(23) }, + { V(26), V( 27), V( 96), V(37), V(22) } }, + { { V( 0), V( 0), V( 80), V(14), V( 8) }, + { V( 0), V( 0), V( 163), V(28), V(12) }, + { V( 0), V( 0), V( 163), V(25), V(15) }, + { V( 0), V( 0), V( 161), V(24), V(14) } }, + { { V( 0), V(-300), V(-300), V(54), V(23) }, + { V( 0), V( 67), V( 128), V(46), V(24) }, + { V( 0), V( 64), V( 130), V(50), V(29) }, + { V( 0), V( 63), V( 127), V(51), V(24) } } }; // 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); + // in front of the king and no enemy pawn on the horizon. + const Value MaxSafetyBonus = V(261); #undef S #undef V @@ -89,14 +101,14 @@ namespace { const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW); const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE); - Bitboard b; + Bitboard b, p, doubled, connected; Square s; - File f; - bool passed, isolated, doubled, opposed, chain, backward, candidate; + bool passed, isolated, opposed, phalanx, backward, unsupported, lever; Score value = SCORE_ZERO; const Square* pl = pos.list(Us); + const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)]; - Bitboard ourPawns = pos.pieces(Us, PAWN); + Bitboard ourPawns = pos.pieces(Us , PAWN); Bitboard theirPawns = pos.pieces(Them, PAWN); e->passedPawns[Us] = 0; @@ -111,27 +123,30 @@ namespace { { assert(pos.piece_on(s) == make_piece(Us, PAWN)); - f = file_of(s); + File f = file_of(s); // This file cannot be semi-open e->semiopenFiles[Us] &= ~(1 << f); - // Our rank plus previous one. Used for chain detection - b = rank_bb(s) | rank_bb(s - pawn_push(Us)); + // Previous rank + p = rank_bb(s - pawn_push(Us)); - // 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)); + // Flag the pawn as passed, isolated, doubled, + // unsupported or connected (but not the backward one). + connected = ourPawns & adjacent_files_bb(f) & (rank_bb(s) | p); + phalanx = connected & rank_bb(s); + unsupported = !(ourPawns & adjacent_files_bb(f) & 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, 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) + // If the pawn is passed, isolated, or connected it cannot be + // backward. If there are friendly pawns behind on adjacent files + // or if it can capture an enemy pawn it cannot be backward either. + if ( (passed | isolated | connected) || (ourPawns & pawn_attack_span(Them, s)) || (pos.attacks_from(s, Us) & theirPawns)) backward = false; @@ -151,14 +166,6 @@ namespace { 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. @@ -169,19 +176,25 @@ namespace { if (isolated) value -= Isolated[opposed][f]; + if (unsupported && !isolated) + value -= UnsupportedPawnPenalty; + if (doubled) - value -= Doubled[opposed][f]; + value -= Doubled[f] / distance(s, frontmost_sq(Us, doubled)); if (backward) value -= Backward[opposed][f]; - if (chain) - value += ChainMember[f]; + if (connected) + value += Connected[opposed][phalanx][relative_rank(Us, s)]; - if (candidate) - value += CandidatePassed[relative_rank(Us, s)]; + if (lever) + value += Lever[relative_rank(Us, s)]; } + b = e->semiopenFiles[Us] ^ 0xFF; + e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0; + return value; } @@ -189,8 +202,26 @@ 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 +/// init() initializes some tables used by evaluation. Instead of 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 (Rank r = RANK_2; r < RANK_8; ++r) + { + int bonus = Seed[r] + (phalanx ? (Seed[r + 1] - Seed[r]) / 2 : 0); + Connected[opposed][phalanx][r] = make_score(bonus / 2, bonus >> opposed); + } +} + + +/// probe() takes a position 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) { @@ -215,59 +246,65 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) { const Color Them = (Us == WHITE ? BLACK : WHITE); - Value safety = MaxSafetyBonus; + enum { NoFriendlyPawn, Unblocked, BlockedByPawn, BlockedByKing }; + Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq)); Bitboard ourPawns = b & pos.pieces(Us); Bitboard theirPawns = b & pos.pieces(Them); - Rank rkUs, rkThem; - File kf = std::max(FILE_B, std::min(FILE_G, file_of(ksq))); + Value safety = MaxSafetyBonus; + File center = std::max(FILE_B, std::min(FILE_G, file_of(ksq))); - for (int f = kf - 1; f <= kf + 1; f++) + for (File f = center - File(1); f <= center + File(1); ++f) { - b = ourPawns & FileBB[f]; - rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1; - safety -= ShelterWeakness[rkUs]; - - b = theirPawns & FileBB[f]; - rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1; - safety -= StormDanger[rkUs == RANK_1 ? 0 : rkThem == rkUs + 1 ? 2 : 1][rkThem]; + b = ourPawns & file_bb(f); + Rank rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1; + + b = theirPawns & file_bb(f); + Rank rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1; + + 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]; } return safety; } -/// 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) { kingSquares[Us] = ksq; - castleRights[Us] = pos.can_castle(Us); - minKPdistance[Us] = 0; + castlingRights[Us] = pos.can_castle(Us); + minKingPawnDistance[Us] = 0; Bitboard pawns = pos.pieces(Us, PAWN); if (pawns) - while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {} + while (!(DistanceRingsBB[ksq][minKingPawnDistance[Us]++] & pawns)) {} if (relative_rank(Us, ksq) > RANK_4) - return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]); + return make_score(0, -16 * minKingPawnDistance[Us]); Value bonus = shelter_storm(pos, ksq); - // If we can castle use the bonus after the castle if is bigger - if (pos.can_castle(make_castle_right(Us, KING_SIDE))) + // 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))); - if (pos.can_castle(make_castle_right(Us, QUEEN_SIDE))) + if (pos.can_castle(MakeCastling::right)) bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1))); - return kingSafety[Us] = make_score(bonus, -16 * minKPdistance[Us]); + return make_score(bonus, -16 * minKingPawnDistance[Us]); } // 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, Square ksq); +template Score Entry::do_king_safety(const Position& pos, Square ksq); } // namespace Pawns