const Score BishopPawns = S( 8, 12);
const Score RookOnPawn = S( 8, 24);
const Score TrappedRook = S(92, 0);
- const Score Checked = S(20, 20);
+ const Score SafeCheck = S(20, 20);
+ const Score OtherCheck = S(10, 10);
const Score ThreatByHangingPawn = S(71, 61);
const Score LooseEnemies = S( 0, 25);
const Score Hanging = S(48, 27);
template<Color Us, bool DoTrace>
Score evaluate_king(const Position& pos, const EvalInfo& ei) {
- const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Color Them = (Us == WHITE ? BLACK : WHITE);
+ const Square Up = (Us == WHITE ? DELTA_N : DELTA_S);
- Bitboard undefended, b, b1, b2, safe;
+ Bitboard undefended, b, b1, b2, safe, other;
int attackUnits;
const Square ksq = pos.square<KING>(Us);
attackUnits += QueenContactCheck * popcount(b);
}
- // Analyse the enemy's safe distance checks for sliders and knights
- safe = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
+ // Analyse the safe enemy's checks which are possible on next move...
+ safe = ~(ei.attackedBy[Us][ALL_PIECES] | pos.pieces(Them));
+
+ // ... and some other potential checks, only requiring the square to be
+ // safe from pawn-attacks, and not being occupied by a blocked pawn.
+ other = ~( ei.attackedBy[Us][PAWN]
+ | (pos.pieces(Them, PAWN) & shift_bb<Up>(pos.pieces(PAWN))));
- b1 = pos.attacks_from<ROOK >(ksq) & safe;
- b2 = pos.attacks_from<BISHOP>(ksq) & safe;
+ b1 = pos.attacks_from<ROOK >(ksq);
+ b2 = pos.attacks_from<BISHOP>(ksq);
// Enemy queen safe checks
- if ((b1 | b2) & ei.attackedBy[Them][QUEEN])
- attackUnits += QueenCheck, score -= Checked;
+ if ((b1 | b2) & ei.attackedBy[Them][QUEEN] & safe)
+ attackUnits += QueenCheck, score -= SafeCheck;
+
+ // Enemy rooks safe and other checks
+ if (b1 & ei.attackedBy[Them][ROOK] & safe)
+ attackUnits += RookCheck, score -= SafeCheck;
+
+ else if (b1 & ei.attackedBy[Them][ROOK] & other)
+ score -= OtherCheck;
+
+ // Enemy bishops safe and other checks
+ if (b2 & ei.attackedBy[Them][BISHOP] & safe)
+ attackUnits += BishopCheck, score -= SafeCheck;
- // Enemy rooks safe checks
- if (b1 & ei.attackedBy[Them][ROOK])
- attackUnits += RookCheck, score -= Checked;
+ else if (b2 & ei.attackedBy[Them][BISHOP] & other)
+ score -= OtherCheck;
- // Enemy bishops safe checks
- if (b2 & ei.attackedBy[Them][BISHOP])
- attackUnits += BishopCheck, score -= Checked;
+ // Enemy knights safe and other checks
+ b = pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT];
+ if (b & safe)
+ attackUnits += KnightCheck, score -= SafeCheck;
- // Enemy knights safe checks
- if (pos.attacks_from<KNIGHT>(ksq) & ei.attackedBy[Them][KNIGHT] & safe)
- attackUnits += KnightCheck, score -= Checked;
+ else if (b & other)
+ score -= OtherCheck;
// Finally, extract the king danger score from the KingDanger[]
// array and subtract the score from the evaluation.