From 10e64e05094e75d89baa4495fa867a8a64195bb7 Mon Sep 17 00:00:00 2001 From: Marco Costalba Date: Wed, 28 Mar 2012 12:44:41 +0200 Subject: [PATCH] Refactor pawns shelter and storm Renamed stuff and added comments. The aim is to make more readable, at least by me ;-) , this newly added part of code. No functional change. Signed-off-by: Marco Costalba --- src/bitboard.h | 10 ----- src/evaluate.cpp | 6 +-- src/pawns.cpp | 112 ++++++++++++++++++++++++++--------------------- src/pawns.h | 11 +++-- 4 files changed, 72 insertions(+), 67 deletions(-) diff --git a/src/bitboard.h b/src/bitboard.h index 85852e5e..6dd07d54 100644 --- a/src/bitboard.h +++ b/src/bitboard.h @@ -263,16 +263,6 @@ extern Square pop_1st_bit(Bitboard* b); #endif -// relative_rank() returns the relative rank of the closest bit set on the Bitboard. -// Only to be used with bitboards that contain a single file. - -template -inline Rank relative_rank(Bitboard b) { - Square s = Us == WHITE ? first_1(b) - : ~last_1(b); - return rank_of(s); -} - extern void print_bitboard(Bitboard b); extern void bitboards_init(); diff --git a/src/evaluate.cpp b/src/evaluate.cpp index 6e515d88..0a500c92 100644 --- a/src/evaluate.cpp +++ b/src/evaluate.cpp @@ -751,8 +751,8 @@ Value do_evaluate(const Position& pos, Value& margin) { int attackUnits; const Square ksq = pos.king_square(Us); - // King shelter - Score score = ei.pi->king_shelter(pos, ksq); + // King shelter and enemy pawns storm + Score score = ei.pi->king_safety(pos, ksq); // King safety. This is quite complicated, and is almost certainly far // from optimally tuned. @@ -774,7 +774,7 @@ Value do_evaluate(const Position& pos, Value& margin) { attackUnits = std::min(25, (ei.kingAttackersCount[Them] * ei.kingAttackersWeight[Them]) / 2) + 3 * (ei.kingAdjacentZoneAttacksCount[Them] + popcount(undefended)) + InitKingDanger[relative_square(Us, ksq)] - - mg_value(ei.pi->king_shelter(pos, ksq)) / 32; + - mg_value(ei.pi->king_safety(pos, ksq)) / 32; // Analyse enemy's safe queen contact checks. First find undefended // squares around the king attacked by enemy queen... diff --git a/src/pawns.cpp b/src/pawns.cpp index eeabcbae..41d2e6f8 100644 --- a/src/pawns.cpp +++ b/src/pawns.cpp @@ -65,18 +65,21 @@ namespace { #undef S - const File ShelterFile[8] = { FILE_B, FILE_B, FILE_C, FILE_D, FILE_E, FILE_F, FILE_G, FILE_G }; + typedef Value V; - inline Value score_non_center_file(const Value v) { - return Value(v * 7 / 16); - } + // Weakness of our pawn shelter in front of the king indexed by [king pawn][rank] + const Value ShelterWeakness[2][8] = + { { V(141), V(0), V(38), V(102), V(128), V(141), V(141), V(141) }, + { V( 61), V(0), V(16), V( 44), V( 56), V( 61), V( 61), V( 61) } }; - typedef Value V; - // Arrays are indexed by rank. Zeroth value is for when no pawn on that file. - const Value PawnShelter[8] = { V(141), V(0), V( 38), V(102), V(128), V(141), V(141), V(141) }; - const Value PawnStorm[8] = { V( 26), V(0), V(128), V( 51), V( 26), V( 0), V( 0), V( 0) }; - // We compute shelter as a penalty for the given color, but shelter is used as a bonus, so we invert it using this as the basis. - const Value PawnShelterBasis = PawnShelter[0] + score_non_center_file(PawnShelter[0]) * 2; + // Danger of enemy pawns moving toward our king indexed by [pawn blocked][rank] + const Value StormDanger[2][8] = + { { V(26), V(0), V(128), V(51), V(26), V(0), V(0), V(0) }, + { V(13), V(0), V( 64), V(25), V(13), V(0), V(0), V(0) } }; + + // Max bonus for king safety. Corresponds to start position with all the pawns + // in front of the king and no enemy pawns on the horizont. + const Value MaxSafetyBonus = V(263); inline Score apply_weight(Score v, Score w) { return make_score((int(mg_value(v)) * mg_value(w)) / 0x100, @@ -222,58 +225,67 @@ Score PawnInfoTable::evaluate_pawns(const Position& pos, Bitboard ourPawns, return value; } + template -int computePawnShelter(const Position &pos, Square ksq) { - const Color Them = (Us == WHITE ? BLACK : WHITE); - const File kingFile = ShelterFile[file_of(ksq)]; - const Bitboard ourPawns = pos.pieces(PAWN, Us) & in_front_bb(Us, ksq); - const Bitboard theirPawns = pos.pieces(PAWN, Them) & (RankBB[rank_of(ksq)] | in_front_bb(Us, ksq)); - - int shelter = 0; - - // Compute king shelter and storm values for the file the king is on, as well as the two adjacent files. - for (int fileOffset = -1; fileOffset <= 1; fileOffset++) { - // Shelter takes full penalty for center file, otherwise it's half penalty - Bitboard shelterFile = ourPawns & FileBB[kingFile + fileOffset]; - Rank shelterClosest = shelterFile ? relative_rank(shelterFile) - : RANK_1; - - shelter += fileOffset == 0 ? PawnShelter[shelterClosest] - : score_non_center_file(PawnShelter[shelterClosest]); - - // Storm takes full penalty, unless there is an enemy pawn blocking us - Bitboard stormFile = theirPawns & FileBB[kingFile + fileOffset]; - Rank stormClosest = stormFile ? relative_rank(stormFile) - : RANK_1; - - shelter += shelterClosest + 1 == stormClosest ? PawnStorm[stormClosest] / 2 - : PawnStorm[stormClosest]; +int PawnInfo::shelter_storm(const Position& pos, Square ksq) { + + const Color Them = (Us == WHITE ? BLACK : WHITE); + + int safety = 0; + Bitboard b = pos.pieces(PAWN) & (in_front_bb(Us, ksq) | RankBB[rank_of(ksq)]); + Bitboard ourPawns = b & pos.pieces(Us) & ~RankBB[rank_of(ksq)]; + Bitboard theirPawns = b & pos.pieces(Them); + Rank rkUs, rkThem; + File kf = file_of(ksq); + + // Compute shelter and storm values for the file the king is on, as well as + // the two adjacent files. Computation is done from the white point of view. + kf = (kf == FILE_A) ? kf++ : (kf == FILE_H) ? kf-- : kf; + + for (int f = kf - 1; f <= kf + 1; f++) + { + // Shelter penalty is higher for the pawn in front of the king + b = ourPawns & FileBB[f]; + rkUs = b ? rank_of(Us == WHITE ? first_1(b) : ~last_1(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 ? first_1(b) : ~last_1(b)) : RANK_1; + safety -= StormDanger[rkThem == rkUs + 1][rkThem]; } - - return shelter; + + return safety; } -/// PawnInfo::updateShelter() calculates and caches king shelter. It is called -/// only when king square changes, about 20% of total king_shelter() calls. + +/// PawnInfo::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. + template -Score PawnInfo::updateShelter(const Position& pos, Square ksq) { - int shelter = 0; +Score PawnInfo::update_safety(const Position& pos, Square ksq) { + + int bonus = 0; if (relative_rank(Us, ksq) <= RANK_4) { - shelter = computePawnShelter(pos, ksq); - if (pos.can_castle(Us == WHITE ? WHITE_OO : BLACK_OO)) - shelter = std::min(shelter, computePawnShelter(pos, relative_square(Us, SQ_G1))); - if (pos.can_castle(Us == WHITE ? WHITE_OOO : BLACK_OOO)) - shelter = std::min(shelter, computePawnShelter(pos, relative_square(Us, SQ_C1))); - shelter = PawnShelterBasis - shelter; + bonus = shelter_storm(pos, ksq); + + // If we can castle use the bonus after the castle if is bigger + if (pos.can_castle(Us == WHITE ? WHITE_OO : BLACK_OO)) + bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_G1))); + + if (pos.can_castle(Us == WHITE ? WHITE_OOO : BLACK_OOO)) + bonus = std::max(bonus, shelter_storm(pos, relative_square(Us, SQ_C1))); + + bonus += MaxSafetyBonus; // Offset to be sure bonus is always positive } kingSquares[Us] = ksq; - kingShelters[Us] = make_score(shelter, 0); + kingShelters[Us] = make_score(bonus, 0); return kingShelters[Us]; } // Explicit template instantiation -template Score PawnInfo::updateShelter(const Position& pos, Square ksq); -template Score PawnInfo::updateShelter(const Position& pos, Square ksq); +template Score PawnInfo::update_safety(const Position& pos, Square ksq); +template Score PawnInfo::update_safety(const Position& pos, Square ksq); diff --git a/src/pawns.h b/src/pawns.h index f2b4441a..1e49a307 100644 --- a/src/pawns.h +++ b/src/pawns.h @@ -46,11 +46,14 @@ public: int has_open_file_to_right(Color c, File f) const; template - Score king_shelter(const Position& pos, Square ksq); + Score king_safety(const Position& pos, Square ksq); private: template - Score updateShelter(const Position& pos, Square ksq); + Score update_safety(const Position& pos, Square ksq); + + template + int shelter_storm(const Position& pos, Square ksq); Key key; Bitboard passedPawns[2]; @@ -100,8 +103,8 @@ inline int PawnInfo::has_open_file_to_right(Color c, File f) const { } template -inline Score PawnInfo::king_shelter(const Position& pos, Square ksq) { - return kingSquares[Us] == ksq ? kingShelters[Us] : updateShelter(pos, ksq); +inline Score PawnInfo::king_safety(const Position& pos, Square ksq) { + return kingSquares[Us] == ksq ? kingShelters[Us] : update_safety(pos, ksq); } #endif // !defined(PAWNS_H_INCLUDED) -- 2.39.2