X-Git-Url: https://git.sesse.net/?p=stockfish;a=blobdiff_plain;f=src%2Fpawns.cpp;h=ee46279d8957a757f0877421c003c6df2b2020e5;hp=718dd575957076d73e62b0bf47350619e826891c;hb=4502a1934f2d624288b635b5901ecda8cefa342c;hpb=1f40cd6d02374277abb5620d88d6fe58d7e9d6f7 diff --git a/src/pawns.cpp b/src/pawns.cpp index 718dd575..ee46279d 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) 2008-2015 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 @@ -24,59 +24,76 @@ #include "bitcount.h" #include "pawns.h" #include "position.h" +#include "thread.h" 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) }}; - - // 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) - }; + S(40, 35), S(40, 35), S(36, 35), S(25, 30) } }; - // 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) - }; + // Backward pawn penalty by opposed flag + const Score Backward[2] = { S(67, 42), S(49, 24) }; - // 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) }; + // Connected pawn bonus by opposed, phalanx, twice supported and rank + Score Connected[2][2][2][RANK_NB]; - // 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) }}; + // 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) + }; + + 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 horizont. - const Value MaxSafetyBonus = V(263); + // in front of the king and no enemy pawn on the horizon. + const Value MaxSafetyBonus = V(258); #undef S #undef V @@ -89,15 +106,14 @@ namespace { const Square Right = (Us == WHITE ? DELTA_NE : DELTA_SW); const Square Left = (Us == WHITE ? DELTA_NW : DELTA_SE); - Bitboard b; + Bitboard b, neighbours, doubled, supported, phalanx; Square s; - File f; - Rank r; - bool passed, isolated, doubled, opposed, chain, backward, candidate; - Score value = SCORE_ZERO; + bool passed, isolated, opposed, backward, lever, connected; + Score score = 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; @@ -112,59 +128,46 @@ namespace { { assert(pos.piece_on(s) == make_piece(Us, PAWN)); - f = file_of(s); - r = rank_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(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 & pawn_attack_span(Them, s)) - && !(pos.attacks_from(s, Us) & theirPawns)) + // Flag the pawn + neighbours = 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]; + phalanx = neighbours & rank_bb(s); + supported = neighbours & rank_bb(s - Up); + connected = supported | phalanx; + isolated = !neighbours; + + // Test for backward pawn. + // If the pawn is passed, isolated, lever or connected it cannot be + // backward. If there are friendly pawns behind on adjacent files + // or if it is sufficiently advanced, it cannot be backward either. + if ( (passed | isolated | lever | connected) + || (ourPawns & pawn_attack_span(Them, s)) + || (relative_rank(Us, s) >= RANK_5)) + backward = false; + else { - // We now know that there are no friendly pawns beside or behind this + // 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 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 - // 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. @@ -173,42 +176,73 @@ namespace { // Score this pawn if (isolated) - value -= Isolated[opposed][f]; + score -= Isolated[opposed][f]; - if (doubled) - value -= Doubled[opposed][f]; + else if (backward) + score -= Backward[opposed]; + + else if (!supported) + score -= UnsupportedPawnPenalty; - if (backward) - value -= Backward[opposed][f]; + if (connected) + score += Connected[opposed][!!phalanx][more_than_one(supported)][relative_rank(Us, s)]; - if (chain) - value += ChainMember[f]; + if (doubled) + score -= Doubled[f] / distance(s, frontmost_sq(Us, doubled)); - if (candidate) - value += CandidatePassed[relative_rank(Us, s)]; + if (lever) + score += Lever[relative_rank(Us, s)]; } - return value; + 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; } } // 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 -/// to recompute everything when the same pawn structure occurs again. +/// 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. -Entry* probe(const Position& pos, Table& entries) { +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 +/// have to recompute all when the same pawns configuration occurs again. + +Entry* probe(const Position& pos) { Key key = pos.pawn_key(); - Entry* e = entries[key]; + Entry* e = pos.this_thread()->pawnsTable[key]; if (e->key == key) return e; e->key = key; - e->value = evaluate(pos, e) - evaluate(pos, e); + e->score = evaluate(pos, e) - evaluate(pos, e); return e; } @@ -221,61 +255,65 @@ 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 = file_of(ksq); - - kf = (kf == FILE_A) ? FILE_B : (kf == FILE_H) ? FILE_G : kf; + 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, Us == WHITE ? lsb(b) : msb(b)) : RANK_1; - safety -= ShelterWeakness[rkUs]; - - b = theirPawns & FileBB[f]; - rkThem = b ? relative_rank(Us, Us == WHITE ? lsb(b) : msb(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); + int minKingPawnDistance = 0; Bitboard pawns = pos.pieces(Us, PAWN); if (pawns) - while (!(DistanceRingsBB[ksq][minKPdistance[Us]++] & pawns)) {} + while (!(DistanceRingBB[ksq][minKingPawnDistance++] & pawns)) {} if (relative_rank(Us, ksq) > RANK_4) - return kingSafety[Us] = make_score(0, -16 * minKPdistance[Us]); + return make_score(0, -16 * minKingPawnDistance); 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); } // 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