along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
-#include <algorithm>
#include <cassert>
#include <cstddef> // For offsetof()
#include <cstring> // For std::memset, std::memcmp
Bitboard blockers = 0;
pinners = 0;
- // Snipers are sliders that attack 's' when a piece is removed
+ // Snipers are sliders that attack 's' when a piece and other snipers are removed
Bitboard snipers = ( (PseudoAttacks[ ROOK][s] & pieces(QUEEN, ROOK))
| (PseudoAttacks[BISHOP][s] & pieces(QUEEN, BISHOP))) & sliders;
+ Bitboard occupancy = pieces() & ~snipers;
while (snipers)
{
Square sniperSq = pop_lsb(&snipers);
- Bitboard b = between_bb(s, sniperSq) & pieces();
+ Bitboard b = between_bb(s, sniperSq) & occupancy;
if (b && !more_than_one(b))
{
Color us = sideToMove;
Square from = from_sq(m);
+ Square to = to_sq(m);
assert(color_of(moved_piece(m)) == us);
assert(piece_on(square<KING>(us)) == make_piece(us, KING));
if (type_of(m) == ENPASSANT)
{
Square ksq = square<KING>(us);
- Square to = to_sq(m);
Square capsq = to - pawn_push(us);
Bitboard occupied = (pieces() ^ from ^ capsq) | to;
&& !(attacks_bb<BISHOP>(ksq, occupied) & pieces(~us, QUEEN, BISHOP));
}
- // If the moving piece is a king, check whether the destination
- // square is attacked by the opponent. Castling moves are checked
- // for legality during move generation.
+ // Castling moves generation does not check if the castling path is clear of
+ // enemy attacks, it is delayed at a later time: now!
+ if (type_of(m) == CASTLING)
+ {
+ // After castling, the rook and king final positions are the same in
+ // Chess960 as they would be in standard chess.
+ to = relative_square(us, to > from ? SQ_G1 : SQ_C1);
+ Direction step = to > from ? WEST : EAST;
+
+ for (Square s = to; s != from; s += step)
+ if (attackers_to(s) & pieces(~us))
+ return false;
+
+ // In case of Chess960, verify that when moving the castling rook we do
+ // not discover some hidden checker.
+ // For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
+ return !chess960
+ || !(attacks_bb<ROOK>(to, pieces() ^ to_sq(m)) & pieces(~us, ROOK, QUEEN));
+ }
+
+ // If the moving piece is a king, check whether the destination square is
+ // attacked by the opponent.
if (type_of(piece_on(from)) == KING)
- return type_of(m) == CASTLING || !(attackers_to(to_sq(m)) & pieces(~us));
+ return !(attackers_to(to) & pieces(~us));
// A non-king move is legal if and only if it is not pinned or it
// is moving along the ray towards or away from the king.
return !(blockers_for_king(us) & from)
- || aligned(from, to_sq(m), square<KING>(us));
+ || aligned(from, to, square<KING>(us));
}
{
// We have already handled promotion moves, so destination
// cannot be on the 8th/1st rank.
- if (rank_of(to) == relative_rank(us, RANK_8))
+ if ((Rank8BB | Rank1BB) & to)
return false;
if ( !(attacks_from<PAWN>(from, us) & pieces(~us) & to) // Not a capture
stmAttackers = attackers & pieces(stm);
// Don't allow pinned pieces to attack (except the king) as long as
- // all pinners are on their original square.
- if (!(st->pinners[~stm] & ~occupied))
+ // any pinners are on their original square.
+ if (st->pinners[~stm] & occupied)
stmAttackers &= ~st->blockersForKing[stm];
// If stm has no more attackers then give up: stm loses