From ff60dafe8d0799f0d6ba083ca566a11465351925 Mon Sep 17 00:00:00 2001 From: Marco Costalba Date: Wed, 11 Feb 2009 11:59:27 +0100 Subject: [PATCH 1/1] Simplify legality check in generate_evasions() Now that we have removed sliders checkers attacks from evasion's set we can simplyfy legality check. No functional change. Signed-off-by: Marco Costalba --- src/movegen.cpp | 17 +++++------------ 1 file changed, 5 insertions(+), 12 deletions(-) diff --git a/src/movegen.cpp b/src/movegen.cpp index 9781f9a9..134127eb 100644 --- a/src/movegen.cpp +++ b/src/movegen.cpp @@ -223,7 +223,8 @@ int generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned) { // Find squares attacked by slider checkers, we will // remove them from king evasions set so to avoid a couple - // of cycles in the slow king evasions legality check loop. + // of cycles in the slow king evasions legality check loop + // and to be able to use square_is_attacked(). Bitboard checkers = pos.checkers(); Bitboard checkersAttacks = EmptyBoardBB; Bitboard b = checkers & (pos.queens() | pos.bishops()); @@ -245,17 +246,9 @@ int generate_evasions(const Position& pos, MoveStack* mlist, Bitboard pinned) { while (b1) { to = pop_1st_bit(&b1); - - // Make sure 'to' is not attacked by the other side. This is a bit ugly, - // because we can't use Position::square_is_attacked. Instead we use - // the low-level bishop_attacks_bb and rook_attacks_bb with the bitboard - // b2 (the occupied squares with the king removed) in order to test whether - // the king will remain in check on the destination square. - if (!( (pos.piece_attacks(to) & pos.knights(them)) - || (pos.pawn_attacks(us, to) & pos.pawns(them)) - || (bishop_attacks_bb(to, b2) & pos.bishops_and_queens(them)) - || (rook_attacks_bb(to, b2) & pos.rooks_and_queens(them)) - || (pos.piece_attacks(to) & pos.kings(them)))) + // Note that we can use square_is_attacked() only because we + // have already removed sliders checkers. + if (!pos.square_is_attacked(to, them)) (*mlist++).move = make_move(ksq, to); } -- 2.39.2