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Simplify Chess 960 castling

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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
This commit is contained in:
bmc4 2021-01-17 15:21:45 -03:00 • committed by Joost VandeVondele
parent 0db374777e
commit dd96095214
1 changed files with 2 additions and 4 deletions
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6
src/position.cpp
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@ -533,11 +533,9 @@ bool Position::legal(Move m) const {
if (attackers_to(s) & pieces(~us)) if (attackers_to(s) & pieces(~us))
return false; return false;
// In case of Chess960, verify that when moving the castling rook we do // In case of Chess960, verify if the Rook blocks some checks
// not discover some hidden checker.
// 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 return !chess960 || !(blockers_for_king(us) & to_sq(m));
|| !(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 // If the moving piece is a king, check whether the destination square is