void Position::set_check_info() const {
- st->blockersForKing[WHITE] = slider_blockers(pieces(BLACK), square<KING>(WHITE), st->pinners[BLACK]);
- st->blockersForKing[BLACK] = slider_blockers(pieces(WHITE), square<KING>(BLACK), st->pinners[WHITE]);
+ update_slider_blockers(WHITE);
+ update_slider_blockers(BLACK);
Square ksq = square<KING>(~sideToMove);
return ss.str();
}
+/// update_slider_blockers() calculates st->blockersForKing[c] and st->pinners[~c],
+/// which store respectively the pieces preventing king of color c from being in check
+/// and the slider pieces of color ~c pinning pieces of color c to the king.
+void Position::update_slider_blockers(Color c) const {
-/// Position::slider_blockers() returns a bitboard of all the pieces (both colors)
-/// that are blocking attacks on the square 's' from 'sliders'. A piece blocks a
-/// slider if removing that piece from the board would result in a position where
-/// square 's' is attacked. For example, a king-attack blocking piece can be either
-/// a pinned or a discovered check piece, according if its color is the opposite
-/// or the same of the color of the slider.
+ Square ksq = square<KING>(c);
-Bitboard Position::slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const {
-
- Bitboard blockers = 0;
- pinners = 0;
+ st->blockersForKing[c] = 0;
+ st->pinners[~c] = 0;
// Snipers are sliders that attack 's' when a piece and other snipers are removed
- Bitboard snipers = ( (attacks_bb< ROOK>(s) & pieces(QUEEN, ROOK))
- | (attacks_bb<BISHOP>(s) & pieces(QUEEN, BISHOP))) & sliders;
+ Bitboard snipers = ( (attacks_bb< ROOK>(ksq) & pieces(QUEEN, ROOK))
+ | (attacks_bb<BISHOP>(ksq) & pieces(QUEEN, BISHOP))) & pieces(~c);
Bitboard occupancy = pieces() ^ snipers;
while (snipers)
{
Square sniperSq = pop_lsb(snipers);
- Bitboard b = between_bb(s, sniperSq) & occupancy;
+ Bitboard b = between_bb(ksq, sniperSq) & occupancy;
if (b && !more_than_one(b))
{
- blockers |= b;
- if (b & pieces(color_of(piece_on(s))))
- pinners |= sniperSq;
+ st->blockersForKing[c] |= b;
+ if (b & pieces(c))
+ st->pinners[~c] |= sniperSq;
}
}
- return blockers;
}
// Attacks to/from a given square
Bitboard attackers_to(Square s) const;
Bitboard attackers_to(Square s, Bitboard occupied) const;
- Bitboard slider_blockers(Bitboard sliders, Square s, Bitboard& pinners) const;
+ void update_slider_blockers(Color c) const;
template<PieceType Pt> Bitboard attacks_by(Color c) const;
// Properties of moves