X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=91da8a7b0858cf748e7ba57231aabfa93b6f238a;hp=135633a3ab9f74d8f1e6654983df16d781a92365;hb=52ae0efccffcce7f095cc4bae7bf90fe7a3b467b;hpb=404c4122ce8f5dd55593668fc87ae46236a71b92 diff --git a/src/pawns.cpp b/src/pawns.cpp index 135633a3..91da8a7b 100644 --- a/src/pawns.cpp +++ b/src/pawns.cpp @@ -51,11 +51,8 @@ namespace { { 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 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] = { @@ -63,15 +60,16 @@ namespace { S(34,68), S(83,166), S(0, 0), S( 0, 0) }; - // 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) } }; + // 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 [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) } }; + // 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) }}; // 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. @@ -91,7 +89,6 @@ namespace { Bitboard b; Square s; File f; - Rank r; bool passed, isolated, doubled, opposed, chain, backward, candidate; Score value = SCORE_ZERO; const Square* pl = pos.list(Us); @@ -99,11 +96,11 @@ 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); - e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & BlackSquares); + e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & DarkSquares); e->pawnsOnSquares[Us][WHITE] = pos.count(Us) - e->pawnsOnSquares[Us][BLACK]; // Loop through all pawns of the current color and score each pawn @@ -112,13 +109,12 @@ namespace { assert(pos.piece_on(s) == make_piece(Us, PAWN)); f = file_of(s); - r = rank_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(r) | rank_bb(Us == WHITE ? r - Rank(1) : r + Rank(1)); + b = rank_bb(s) | rank_bb(s - pawn_push(Us)); // Flag the pawn as passed, isolated, doubled or member of a pawn // chain (but not the backward one). @@ -128,29 +124,25 @@ namespace { opposed = theirPawns & forward_bb(Us, s); passed = !(theirPawns & passed_pawn_mask(Us, s)); - // Test for backward pawn - backward = false; - + // 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) - && !(ourPawns & pawn_attack_span(Them, s)) - && !(pos.attacks_from(s, Us) & theirPawns)) + if ( (passed | isolated | chain) + || (ourPawns & pawn_attack_span(Them, s)) + || (pos.attacks_from(s, Us) & theirPawns)) + backward = false; + else { // 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); + // 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)); - // 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); - - // 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; } @@ -181,10 +173,15 @@ namespace { 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; + } } return value; @@ -194,6 +191,22 @@ namespace { namespace Pawns { +/// init() initializes some tables by formula instead of hard-code 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. @@ -222,24 +235,20 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) { Value safety = MaxSafetyBonus; Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, rank_of(ksq)) | rank_bb(ksq)); - Bitboard ourPawns = b & pos.pieces(Us) & ~rank_bb(ksq); + Bitboard ourPawns = b & pos.pieces(Us); 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; + 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) { - // 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); + rkUs = b ? relative_rank(Us, backmost_sq(Us, b)) : RANK_1; + safety -= ShelterWeakness[rkUs]; + + 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]; } return safety;