X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=39bd689f2e30c921c60030a5287d5f6ec8b84489;hp=fece246b1c999a31611a8b8661b4e97d8e9520e2;hb=cf0a2a26a9e2640dc86b26a998fb7a71a5c20b90;hpb=aecdbfc4a000c72fcc2642f54ce83967913a16ba diff --git a/src/pawns.cpp b/src/pawns.cpp index fece246b..39bd689f 100644 --- a/src/pawns.cpp +++ b/src/pawns.cpp @@ -30,38 +30,35 @@ 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) }}; + 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 chain membership bonus by file and rank (initialized by formula) + Score ChainMember[FILE_NB][RANK_NB]; // 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) - }; + S(34,68), S(83,166), S(0, 0), S( 0, 0) }; + + // Bonus for file distance of the two outermost pawns + const Score PawnsFileSpan = S(0, 10); // Weakness of our pawn shelter in front of the king indexed by [rank] const Value ShelterWeakness[RANK_NB] = @@ -72,10 +69,10 @@ namespace { 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) }}; + { V( 0), 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. + // in front of the king and no enemy pawn on the horizon. const Value MaxSafetyBonus = V(263); #undef S @@ -99,7 +96,7 @@ namespace { Bitboard ourPawns = pos.pieces(Us, PAWN); Bitboard theirPawns = pos.pieces(Them, PAWN); - e->passedPawns[Us] = 0; + e->passedPawns[Us] = e->candidatePawns[Us] = 0; e->kingSquares[Us] = SQ_NONE; e->semiopenFiles[Us] = 0xFF; e->pawnAttacks[Us] = shift_bb(ourPawns) | shift_bb(ourPawns); @@ -130,7 +127,7 @@ namespace { // 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. + // or if it 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)) @@ -140,24 +137,20 @@ namespace { // 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); + // 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)); - // The friendly pawn needs to be at least two ranks closer than the - // enemy pawn in order to help the potentially backward pawn advance. + // 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)); - // A not passed pawn is a candidate to become passed if it is free to + // 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 + // pawn on adjacent files is higher than or equal to 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 @@ -174,16 +167,29 @@ namespace { value -= Isolated[opposed][f]; if (doubled) - value -= Doubled[opposed][f]; + value -= Doubled[f]; if (backward) value -= Backward[opposed][f]; if (chain) - value += ChainMember[f]; + value += ChainMember[f][relative_rank(Us, s)]; if (candidate) + { value += CandidatePassed[relative_rank(Us, s)]; + + if (!doubled) + e->candidatePawns[Us] |= s; + } + } + + // In endgame it's better to have pawns on both wings. So give a bonus according + // to file distance between left and right outermost pawns. + if (pos.count(Us) > 1) + { + b = ~e->semiopenFiles[Us] & 0xFF; + value += PawnsFileSpan * int(msb(b) - lsb(b)); } return value; @@ -193,6 +199,22 @@ namespace { namespace Pawns { +/// init() initializes some tables by formula instead of hard-coding their values + +void init() { + + const int chainByFile[8] = { 1, 3, 3, 4, 4, 3, 3, 1 }; + int bonus; + + for (Rank r = RANK_1; r < RANK_8; ++r) + for (File f = FILE_A; f <= FILE_H; ++f) + { + bonus = r * (r-1) * (r-2) + chainByFile[f] * (r/2 + 1); + ChainMember[f][r] = make_score(bonus, bonus); + } +} + + /// 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. @@ -226,14 +248,14 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) { Rank rkUs, rkThem; File kf = std::max(FILE_B, std::min(FILE_G, file_of(ksq))); - for (int f = kf - 1; f <= kf + 1; f++) + for (File f = kf - File(1); f <= kf + File(1); ++f) { - b = ourPawns & FileBB[f]; - rkUs = b ? relative_rank(Us, lsb(Us, b)) : RANK_1; + b = ourPawns & file_bb(f); + rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1; safety -= ShelterWeakness[rkUs]; - b = theirPawns & FileBB[f]; - rkThem = b ? relative_rank(Us, lsb(Us, b)) : RANK_1; + b = theirPawns & file_bb(f); + rkThem = b ? relative_rank(Us, frontmost_sq(Them, b)) : RANK_1; safety -= StormDanger[rkUs == RANK_1 ? 0 : rkThem == rkUs + 1 ? 2 : 1][rkThem]; } @@ -241,14 +263,15 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) { } -/// 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::update_safety() calculates and caches 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) { kingSquares[Us] = ksq; - castleRights[Us] = pos.can_castle(Us); + castlingFlags[Us] = pos.can_castle(Us); minKPdistance[Us] = 0; Bitboard pawns = pos.pieces(Us, PAWN); @@ -260,11 +283,11 @@ Score Entry::update_safety(const Position& pos, Square ksq) { 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(make_castling_flag(Us, KING_SIDE))) 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(make_castling_flag(Us, QUEEN_SIDE))) bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1))); return kingSafety[Us] = make_score(bonus, -16 * minKPdistance[Us]);