constexpr Color Them = ~Us;
constexpr Direction Up = pawn_push(Us);
+ constexpr Direction Down = -Up;
auto king_proximity = [&](Color c, Square s) {
return std::min(distance(pos.square<KING>(c), s), 5);
};
- Bitboard b, bb, squaresToQueen, unsafeSquares;
+ Bitboard b, bb, squaresToQueen, unsafeSquares, candidatePassers, leverable;
Score score = SCORE_ZERO;
b = pe->passed_pawns(Us);
+ candidatePassers = b & shift<Down>(pos.pieces(Them, PAWN));
+ if (candidatePassers)
+ {
+ // Can we lever the blocker of a candidate passer?
+ leverable = shift<Up>(pos.pieces(Us, PAWN))
+ & ~pos.pieces(Them)
+ & (~attackedBy2[Them] | attackedBy[Us][ALL_PIECES])
+ & (~(attackedBy[Them][KNIGHT] | attackedBy[Them][BISHOP])
+ | (attackedBy[Us ][KNIGHT] | attackedBy[Us ][BISHOP]));
+
+ // Remove candidate otherwise
+ b &= ~candidatePassers
+ | shift<WEST>(leverable)
+ | shift<EAST>(leverable);
+ }
+
while (b)
{
Square s = pop_lsb(&b);