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Micro-optmize castling moves

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Pre compute castle path so to quickly test
for impeded rule.

This speeds up perft on starting position
of more than 2%.

No functional change

Signed-off-by: Marco Costalba <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba
2012-02-27 12:11:18 +01:00
parent 5bb766e826
commit 34178205fc
3 changed files with 29 additions and 19 deletions
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15
src/movegen.cpp
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@@ -40,7 +40,7 @@ namespace {
const CastleRight CR[] = { Side ? WHITE_OOO : WHITE_OO,
Side ? BLACK_OOO : BLACK_OO };
if (!pos.can_castle(CR[us]))
if (pos.castle_impeded(CR[us]) || !pos.can_castle(CR[us]))
return mlist;
// After castling, the rook and king final positions are the same in Chess960
@@ -48,24 +48,15 @@ namespace {
Square kfrom = pos.king_square(us);
Square rfrom = pos.castle_rook_square(CR[us]);
Square kto = relative_square(us, Side == KING_SIDE ? SQ_G1 : SQ_C1);
Square rto = relative_square(us, Side == KING_SIDE ? SQ_F1 : SQ_D1);
Bitboard enemies = pos.pieces(~us);
assert(!pos.in_check());
assert(pos.piece_on(kfrom) == make_piece(us, KING));
assert(pos.piece_on(rfrom) == make_piece(us, ROOK));
// Unimpeded rule: All the squares between the king's initial and final squares
// (including the final square), and all the squares between the rook's initial
// and final squares (including the final square), must be vacant except for
// the king and castling rook.
for (Square s = std::min(rfrom, rto), e = std::max(rfrom, rto); s <= e; s++)
if (s != kfrom && s != rfrom && !pos.square_is_empty(s))
return mlist;
for (Square s = std::min(kfrom, kto), e = std::max(kfrom, kto); s <= e; s++)
if ( (s != kfrom && s != rfrom && !pos.square_is_empty(s))
||(pos.attackers_to(s) & enemies))
if ( s != kfrom // We are not in check
&& (pos.attackers_to(s) & enemies))
return mlist;
// Because we generate only legal castling moves we need to verify that