}
-/// Position:pinned_pieces() returns a bitboard of all pinned (against the
-/// king) pieces for the given color.
-Bitboard Position::pinned_pieces(Color c) const {
-
- Bitboard p;
- Square ksq = king_square(c);
- return hidden_checks<ROOK, true>(c, ksq, p) | hidden_checks<BISHOP, true>(c, ksq, p);
-}
-
+/// Position:hidden_checkers<>() returns a bitboard of all pinned (against the
+/// king) pieces for the given color and for the given pinner type. Or, when
+/// template parameter FindPinned is false, the pieces of the given color
+/// candidate for a discovery check against the enemy king.
+/// Note that checkersBB bitboard must be already updated.
-/// Position:discovered_check_candidates() returns a bitboard containing all
-/// pieces for the given side which are candidates for giving a discovered
-/// check. The code is almost the same as the function for finding pinned
-/// pieces.
+template<bool FindPinned>
+Bitboard Position::hidden_checkers(Color c) const {
-Bitboard Position::discovered_check_candidates(Color c) const {
+ Bitboard pinners, result = EmptyBoardBB;
- Bitboard p;
- Square ksq = king_square(opposite_color(c));
- return hidden_checks<ROOK, false>(c, ksq, p) | hidden_checks<BISHOP, false>(c, ksq, p);
-}
+ // Pinned pieces protect our king, dicovery checks attack
+ // the enemy king.
+ Square ksq = king_square(FindPinned ? c : opposite_color(c));
+ // Pinners are sliders, not checkers, that give check when
+ // candidate pinned is removed.
+ pinners = (rooks_and_queens(FindPinned ? opposite_color(c) : c) & RookPseudoAttacks[ksq])
+ | (bishops_and_queens(FindPinned ? opposite_color(c) : c) & BishopPseudoAttacks[ksq]);
-/// Position:hidden_checks<>() returns a bitboard of all pinned (against the
-/// king) pieces for the given color and for the given pinner type. Or, when
-/// template parameter FindPinned is false, the pinned pieces of opposite color
-/// that are, indeed, the pieces candidate for a discovery check.
-/// Note that checkersBB bitboard must be already updated.
-template<PieceType Piece, bool FindPinned>
-Bitboard Position::hidden_checks(Color c, Square ksq, Bitboard& pinners) const {
+ if (FindPinned && pinners)
+ pinners &= ~st->checkersBB;
- Square s;
- Bitboard sliders, result = EmptyBoardBB;
+ while (pinners)
+ {
+ Square s = pop_1st_bit(&pinners);
+ Bitboard b = squares_between(s, ksq) & occupied_squares();
- if (Piece == ROOK) // Resolved at compile time
- sliders = rooks_and_queens(FindPinned ? opposite_color(c) : c) & RookPseudoAttacks[ksq];
- else
- sliders = bishops_and_queens(FindPinned ? opposite_color(c) : c) & BishopPseudoAttacks[ksq];
+ assert(b);
- if (sliders && (!FindPinned || (sliders & ~st->checkersBB)))
- {
- // King blockers are candidate pinned pieces
- Bitboard candidate_pinned = piece_attacks<Piece>(ksq) & pieces_of_color(c);
-
- // Pinners are sliders, not checkers, that give check when
- // candidate pinned are removed.
- pinners = (FindPinned ? sliders & ~st->checkersBB : sliders);
-
- if (Piece == ROOK)
- pinners &= rook_attacks_bb(ksq, occupied_squares() ^ candidate_pinned);
- else
- pinners &= bishop_attacks_bb(ksq, occupied_squares() ^ candidate_pinned);
-
- // Finally for each pinner find the corresponding pinned piece (if same color of king)
- // or discovery checker (if opposite color) among the candidates.
- Bitboard p = pinners;
- while (p)
- {
- s = pop_1st_bit(&p);
- result |= (squares_between(s, ksq) & candidate_pinned);
- }
+ if ( !(b & (b - 1)) // Only one bit set?
+ && (b & pieces_of_color(c))) // Is an our piece?
+ result |= b;
}
- else
- pinners = EmptyBoardBB;
-
return result;
}
template<PieceType Piece>
void update_checkers(Bitboard* pCheckersBB, Square ksq, Square from, Square to, Bitboard dcCandidates);
- template<PieceType Piece, bool FindPinned>
- Bitboard hidden_checks(Color c, Square ksq, Bitboard& pinners) const;
+ template<bool FindPinned>
+ Bitboard hidden_checkers(Color c) const;
// Computing hash keys from scratch (for initialization and debugging)
Key compute_key() const;
return st->checkersBB;
}
+inline Bitboard Position::pinned_pieces(Color c) const {
+ return hidden_checkers<true>(c);
+}
+
+inline Bitboard Position::discovered_check_candidates(Color c) const {
+ return hidden_checkers<false>(c);
+}
+
inline bool Position::is_check() const {
return st->checkersBB != EmptyBoardBB;
}