#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,
return value;
}
+
template<Color Us>
-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<Us>(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<Us>(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<Color Us>
-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<Us>(pos, ksq);
- if (pos.can_castle(Us == WHITE ? WHITE_OO : BLACK_OO))
- shelter = std::min(shelter, computePawnShelter<Us>(pos, relative_square(Us, SQ_G1)));
- if (pos.can_castle(Us == WHITE ? WHITE_OOO : BLACK_OOO))
- shelter = std::min(shelter, computePawnShelter<Us>(pos, relative_square(Us, SQ_C1)));
- shelter = PawnShelterBasis - shelter;
+ bonus = shelter_storm<Us>(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<Us>(pos, relative_square(Us, SQ_G1)));
+
+ if (pos.can_castle(Us == WHITE ? WHITE_OOO : BLACK_OOO))
+ bonus = std::max(bonus, shelter_storm<Us>(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<WHITE>(const Position& pos, Square ksq);
-template Score PawnInfo::updateShelter<BLACK>(const Position& pos, Square ksq);
+template Score PawnInfo::update_safety<WHITE>(const Position& pos, Square ksq);
+template Score PawnInfo::update_safety<BLACK>(const Position& pos, Square ksq);
projects / stockfish / blobdiff