X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=b26b1be656cda8a599ca2a00d8405fd45317ac9b;hp=5b64ac6163091814e53150544b2add49c93e10b0;hb=296534f23489e6d95ba7ce1bb35e8a2cbf9a5a9d;hpb=f84f04742a30166c2751de28245e11922da132fb diff --git a/src/pawns.cpp b/src/pawns.cpp index 5b64ac61..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 @@ -17,6 +17,7 @@ along with this program. If not, see . */ +#include #include #include "bitboard.h" @@ -29,129 +30,141 @@ namespace { #define V Value #define S(mg, eg) make_score(mg, eg) - // Doubled pawn penalty by opposed flag and file - const Score DoubledPawnPenalty[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 IsolatedPawnPenalty[2][FILE_NB] = { + 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 BackwardPawnPenalty[2][FILE_NB] = { + 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 ChainBonus[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 CandidateBonus[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) - }; - - const Score PawnStructureWeight = S(233, 201); - - // 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) } }; - - // 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) } }; + 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 template - Score evaluate_pawns(const Position& pos, Bitboard ourPawns, - Bitboard theirPawns, Pawns::Entry* e) { + Score evaluate(const Position& pos, Pawns::Entry* e) { - const Color Them = (Us == WHITE ? BLACK : WHITE); + 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); - Bitboard b; + Bitboard b, p, doubled, connected; Square s; - File f; - Rank r; - bool passed, isolated, doubled, opposed, chain, backward, candidate; + bool passed, isolated, opposed, phalanx, backward, unsupported, lever; Score value = SCORE_ZERO; - const Square* pl = pos.piece_list(Us, PAWN); + const Square* pl = pos.list(Us); + const Bitboard* pawnAttacksBB = StepAttacksBB[make_piece(Us, PAWN)]; + + Bitboard ourPawns = pos.pieces(Us , PAWN); + Bitboard theirPawns = pos.pieces(Them, PAWN); + + 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]; // 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)); - f = file_of(s); - r = rank_of(s); - - // This file cannot be half open - e->halfOpenFiles[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)); - - // 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)); - - // Test for backward pawn - backward = false; - - // 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 & attack_span_mask(Them, s)) - && !(pos.attacks_from(s, Us) & theirPawns)) + File f = file_of(s); + + // This file cannot be semi-open + e->semiopenFiles[Us] &= ~(1 << f); + + // Previous rank + p = rank_bb(s - pawn_push(Us)); + + // 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 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; + 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))) - Us == WHITE ? b <<= 8 : b >>= 8; - - // The friendly pawn needs to be at least two ranks closer than the - // enemy pawn in order to help the potentially backward pawn advance. - backward = (b | (Us == WHITE ? b << 8 : b >> 8)) & theirPawns; + // 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 | (attack_span_mask(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 = attack_span_mask(Them, s + pawn_push(Us)) & ourPawns) != 0 - && popcount(b) >= popcount(attack_span_mask(Us, s) & 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 @@ -161,35 +174,54 @@ namespace { // Score this pawn if (isolated) - value -= IsolatedPawnPenalty[opposed][f]; + value -= Isolated[opposed][f]; + + if (unsupported && !isolated) + value -= UnsupportedPawnPenalty; if (doubled) - value -= DoubledPawnPenalty[opposed][f]; + value -= Doubled[f] / distance(s, frontmost_sq(Us, doubled)); if (backward) - value -= BackwardPawnPenalty[opposed][f]; + value -= Backward[opposed][f]; - if (chain) - value += ChainBonus[f]; + if (connected) + value += Connected[opposed][phalanx][relative_rank(Us, s)]; - if (candidate) - value += CandidateBonus[relative_rank(Us, s)]; + if (lever) + value += Lever[relative_rank(Us, s)]; } - e->pawnsOnSquares[Us][BLACK] = popcount(ourPawns & BlackSquares); - e->pawnsOnSquares[Us][WHITE] = pos.piece_count(Us, PAWN) - e->pawnsOnSquares[Us][BLACK]; - - e->pawnsOnSquares[Them][BLACK] = popcount(theirPawns & BlackSquares); - e->pawnsOnSquares[Them][WHITE] = pos.piece_count(Them, PAWN) - e->pawnsOnSquares[Them][BLACK]; + b = e->semiopenFiles[Us] ^ 0xFF; + e->pawnSpan[Us] = b ? int(msb(b) - lsb(b)) : 0; return value; } -} + +} // 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) { @@ -197,27 +229,11 @@ Entry* probe(const Position& pos, Table& entries) { Key key = pos.pawn_key(); Entry* e = entries[key]; - // If e->key matches the position's pawn hash key, it means that we - // have analysed this pawn structure before, and we can simply return - // the information we found the last time instead of recomputing it. if (e->key == key) return e; e->key = key; - e->passedPawns[WHITE] = e->passedPawns[BLACK] = 0; - e->kingSquares[WHITE] = e->kingSquares[BLACK] = SQ_NONE; - e->halfOpenFiles[WHITE] = e->halfOpenFiles[BLACK] = 0xFF; - - Bitboard wPawns = pos.pieces(WHITE, PAWN); - Bitboard bPawns = pos.pieces(BLACK, PAWN); - e->pawnAttacks[WHITE] = ((wPawns & ~FileHBB) << 9) | ((wPawns & ~FileABB) << 7); - e->pawnAttacks[BLACK] = ((bPawns & ~FileHBB) >> 7) | ((bPawns & ~FileABB) >> 9); - - e->value = evaluate_pawns(pos, wPawns, bPawns, e) - - evaluate_pawns(pos, bPawns, wPawns, e); - - e->value = apply_weight(e->value, PawnStructureWeight); - + e->value = evaluate(pos, e) - evaluate(pos, e); return e; } @@ -230,63 +246,65 @@ Value Entry::shelter_storm(const Position& pos, Square ksq) { const Color Them = (Us == WHITE ? BLACK : WHITE); - Value safety = MaxSafetyBonus; - Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, ksq) | rank_bb(ksq)); - Bitboard ourPawns = b & pos.pieces(Us) & ~rank_bb(ksq); - Bitboard theirPawns = b & pos.pieces(Them); - Rank rkUs, rkThem; - File kf = file_of(ksq); + enum { NoFriendlyPawn, Unblocked, BlockedByPawn, BlockedByKing }; - kf = (kf == FILE_A) ? FILE_B : (kf == FILE_H) ? FILE_G : kf; + 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); + 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) { - // 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); + 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