a little cleanup, and small speedup (about 0.3%) for Chess 960.
Verified with perft on a large set of chess960 positions.
Closes https://github.com/official-stockfish/Stockfish/pull/3317
No functional change
if (attackers_to(s) & pieces(~us))
return false;
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.
+ // In case of Chess960, verify if the Rook blocks some checks
// For instance an enemy queen in SQ_A1 when castling rook is in SQ_B1.
// 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));
+ return !chess960 || !(blockers_for_king(us) & to_sq(m));
}
// If the moving piece is a king, check whether the destination square is
}
// If the moving piece is a king, check whether the destination square is