// attacked by a given color and piece type (can be also ALL_PIECES).
Bitboard attackedBy[COLOR_NB][PIECE_TYPE_NB];
+ // attackedBy2[color] are the squares attacked by 2 pieces of a given color,
+ // possibly via x-ray or by one pawn and one piece. Diagonal x-ray through
+ // pawn or squares attacked by 2 pawns are not explicitly added.
+ Bitboard attackedBy2[COLOR_NB];
+
// kingRing[color] is the zone around the king which is considered
// by the king safety evaluation. This consists of the squares directly
// adjacent to the king, and the three (or two, for a king on an edge file)
// game, indexed by piece type and number of attacked squares in the MobilityArea.
const Score MobilityBonus[][32] = {
{}, {},
- { S(-75,-76), S(-56,-54), S(- 9,-26), S( -2,-10), S( 6, 5), S( 15, 11), // Knights
+ { S(-75,-76), S(-56,-54), S( -9,-26), S( -2,-10), S( 6, 5), S( 15, 11), // Knights
S( 22, 26), S( 30, 28), S( 36, 29) },
{ S(-48,-58), S(-21,-19), S( 16, -2), S( 26, 12), S( 37, 22), S( 51, 42), // Bishops
S( 54, 54), S( 63, 58), S( 65, 63), S( 71, 70), S( 79, 74), S( 81, 86),
const Score BishopPawns = S( 8, 12);
const Score RookOnPawn = S( 8, 24);
const Score TrappedRook = S(92, 0);
+ const Score CloseEnemies = S( 7, 0);
const Score SafeCheck = S(20, 20);
const Score OtherCheck = S(10, 10);
const Score ThreatByHangingPawn = S(71, 61);
// in KingDanger[]. Various little "meta-bonuses" measuring the strength
// of the enemy attack are added up into an integer, which is used as an
// index to KingDanger[].
- Score KingDanger[512];
+ Score KingDanger[400];
// KingAttackWeights[PieceType] contains king attack weights by piece type
const int KingAttackWeights[PIECE_TYPE_NB] = { 0, 0, 7, 5, 4, 1 };
const Square Down = (Us == WHITE ? DELTA_S : DELTA_N);
ei.pinnedPieces[Us] = pos.pinned_pieces(Us);
- Bitboard b = ei.attackedBy[Them][KING] = pos.attacks_from<KING>(pos.square<KING>(Them));
+ Bitboard b = ei.attackedBy[Them][KING];
ei.attackedBy[Them][ALL_PIECES] |= b;
ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][PAWN] = ei.pi->pawn_attacks(Us);
+ ei.attackedBy2[Us] = ei.attackedBy[Us][PAWN] & ei.attackedBy[Us][KING];
// Init king safety tables only if we are going to use them
if (pos.non_pawn_material(Us) >= QueenValueMg)
if (ei.pinnedPieces[Us] & s)
b &= LineBB[pos.square<KING>(Us)][s];
+ ei.attackedBy2[Us] |= ei.attackedBy[Us][ALL_PIECES] & b;
ei.attackedBy[Us][ALL_PIECES] |= ei.attackedBy[Us][Pt] |= b;
if (b & ei.kingRing[Them])
if (Pt == QUEEN)
{
// Penalty if any relative pin or discovered attack against the queen
- if (pos.slider_blockers(pos.pieces(), pos.pieces(Them, ROOK, BISHOP), s))
+ if (pos.slider_blockers(pos.pieces(Them, ROOK, BISHOP), s))
score -= WeakQueen;
}
}
// evaluate_king() assigns bonuses and penalties to a king of a given color
+ const Bitboard WhiteCamp = Rank1BB | Rank2BB | Rank3BB | Rank4BB | Rank5BB;
+ const Bitboard BlackCamp = Rank8BB | Rank7BB | Rank6BB | Rank5BB | Rank4BB;
+ const Bitboard QueenSide = FileABB | FileBBB | FileCBB | FileDBB;
+ const Bitboard CenterFiles = FileCBB | FileDBB | FileEBB | FileFBB;
+ const Bitboard KingSide = FileEBB | FileFBB | FileGBB | FileHBB;
+
+ const Bitboard KingFlank[COLOR_NB][FILE_NB] = {
+ { QueenSide & WhiteCamp, QueenSide & WhiteCamp, QueenSide & WhiteCamp, CenterFiles & WhiteCamp,
+ CenterFiles & WhiteCamp, KingSide & WhiteCamp, KingSide & WhiteCamp, KingSide & WhiteCamp },
+ { QueenSide & BlackCamp, QueenSide & BlackCamp, QueenSide & BlackCamp, CenterFiles & BlackCamp,
+ CenterFiles & BlackCamp, KingSide & BlackCamp, KingSide & BlackCamp, KingSide & BlackCamp },
+ };
+
template<Color Us, bool DoTrace>
Score evaluate_king(const Position& pos, const EvalInfo& ei) {
if (ei.kingAttackersCount[Them])
{
// Find the attacked squares which are defended only by the king...
- undefended = ei.attackedBy[Them][ALL_PIECES]
- & ei.attackedBy[Us][KING]
- & ~( ei.attackedBy[Us][PAWN] | ei.attackedBy[Us][KNIGHT]
- | ei.attackedBy[Us][BISHOP] | ei.attackedBy[Us][ROOK]
- | ei.attackedBy[Us][QUEEN]);
+ undefended = ei.attackedBy[Them][ALL_PIECES]
+ & ei.attackedBy[Us][KING]
+ & ~ei.attackedBy2[Us];
// ... and those which are not defended at all in the larger king ring
b = ei.attackedBy[Them][ALL_PIECES] & ~ei.attackedBy[Us][ALL_PIECES]
// Analyse the enemy's safe queen contact checks. Firstly, find the
// undefended squares around the king reachable by the enemy queen...
b = undefended & ei.attackedBy[Them][QUEEN] & ~pos.pieces(Them);
- if (b)
- {
- // ...and then remove squares not supported by another enemy piece
- b &= ei.attackedBy[Them][PAWN] | ei.attackedBy[Them][KNIGHT]
- | ei.attackedBy[Them][BISHOP] | ei.attackedBy[Them][ROOK]
- | ei.attackedBy[Them][KING];
- attackUnits += QueenContactCheck * popcount(b);
- }
+ // ...and keep squares supported by another enemy piece
+ attackUnits += QueenContactCheck * popcount(b & ei.attackedBy2[Them]);
// Analyse the safe enemy's checks which are possible on next move...
safe = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
if ((b1 | b2) & ei.attackedBy[Them][QUEEN] & safe)
attackUnits += QueenCheck, score -= SafeCheck;
+ // For other pieces, also consider the square safe if attacked twice,
+ // and only defended by a queen.
+ safe |= ei.attackedBy2[Them]
+ & ~(ei.attackedBy2[Us] | pos.pieces(Them))
+ & ei.attackedBy[Us][QUEEN];
+
// Enemy rooks safe and other checks
if (b1 & ei.attackedBy[Them][ROOK] & safe)
attackUnits += RookCheck, score -= SafeCheck;
score -= KingDanger[std::max(std::min(attackUnits, 399), 0)];
}
+ // King tropism: firstly, find squares that opponent attacks in our king flank
+ b = ei.attackedBy[Them][ALL_PIECES] & KingFlank[Us][file_of(ksq)];
+
+ assert(((Us == WHITE ? b << 4 : b >> 4) & b) == 0);
+ assert(popcount(Us == WHITE ? b << 4 : b >> 4) == popcount(b));
+
+ // Secondly, add the squares which are attacked twice in that flank and
+ // which are not defended by our pawns.
+ b = (Us == WHITE ? b << 4 : b >> 4)
+ | (b & ei.attackedBy2[Them] & ~ei.attackedBy[Us][PAWN]);
+
+ score -= CloseEnemies * popcount(b);
+
if (DoTrace)
Trace::add(KING, Us, score);
// ...count safe + (behind & safe) with a single popcount
int bonus = popcount((Us == WHITE ? safe << 32 : safe >> 32) | (behind & safe));
- int weight = pos.count<KNIGHT>(Us) + pos.count<BISHOP>(Us)
- + pos.count<KNIGHT>(Them) + pos.count<BISHOP>(Them);
+ bonus = std::min(16, bonus);
+ int weight = pos.count<ALL_PIECES>(Us) - 2 * ei.pi->open_files();
- return make_score(bonus * weight * weight * 2 / 11, 0);
+ return make_score(bonus * weight * weight / 18, 0);
}
// Endings where weaker side can place his king in front of the opponent's
// pawns are drawish.
else if ( abs(eg) <= BishopValueEg
- && ei.pi->pawn_span(strongSide) <= 1
+ && pos.count<PAWN>(strongSide) <= 2
&& !pos.pawn_passed(~strongSide, pos.square<KING>(~strongSide)))
- sf = ei.pi->pawn_span(strongSide) ? ScaleFactor(51) : ScaleFactor(37);
+ sf = ScaleFactor(37 + 7 * pos.count<PAWN>(strongSide));
}
return sf;
// Initialize attack and king safety bitboards
ei.attackedBy[WHITE][ALL_PIECES] = ei.attackedBy[BLACK][ALL_PIECES] = 0;
+ ei.attackedBy[WHITE][KING] = pos.attacks_from<KING>(pos.square<KING>(WHITE));
+ ei.attackedBy[BLACK][KING] = pos.attacks_from<KING>(pos.square<KING>(BLACK));
eval_init<WHITE>(pos, ei);
eval_init<BLACK>(pos, ei);
projects / stockfish / blobdiff