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Simplify legality check in generate_evasions()

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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 <mcostalba@gmail.com>
This commit is contained in:
Marco Costalba 2009-02-11 11:59:27 +01:00
parent 214f9dcc27
commit ff60dafe8d
1 changed files with 5 additions and 12 deletions
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17
src/movegen.cpp
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@ -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<KNIGHT>(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<KING>(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);
}