Use the newly introduced LineBB[] to simplify this
super hot-path function.
Verified with perft we don't have any speed regression, although
the number of squares removed is less than before in case of
contact check.
Insipred by DiscoCheck implementation.
Perft numbers are the same, but we have an harmless functional
change due to reorder of moves, because now some illegal moves
are no more detected at generation time, but in the search.
bench: 8331357
We have only one call place so inline its content.
BTW, function is already declared as FORCE_INLINE.
Also some small refactoring while there.
No functional change.
We have a crash with this position:
rkqbnnbr/pppppppp/8/8/8/8/PPPPPPPP/RKQBNNBR w HAha -
What happens is that even if we are castling QUEEN_SIDE,
in this case we have kfrom (B8) < kto (C8) so the loop
that checks for attackers runs forever leading to a crash.
The fix is to check for (kto > kfrom) instead of
Side == KING_SIDE, but this is slower in the normal case of
ortodhox chess, so rewrite generate_castle() to handle the
chess960 case as a template parameter and allow the compiler
to optimize out the comparison in case of normal chess.
Reported by Ray Banks.
The trick here is to check for legality only in the
(rare) cases we have pinned pieces or a king move
or an en-passant.
This trick is able to increase the speed of perft
of more then 20%!
No functional change.
Further reduce redundancy in move generation.
Veirifed no speed regression on MSVC, Clang and gcc.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Greatly simplify these very performace critical functions.
Amazingly we don't have any speed regression actually under
MSVC we have the same assembly for generate_moves() !
In generate_direct_checks() 'target' is calculated only
once being a loop invariant.
On Clang there is even a slight speed up.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
It seems more accurate: lsb is clear while 'first
bit' depends from where you look at the bitboard.
And fix compile in case of 64 bits platforms that
do not use BSFQ intrinsics.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Let first argument to be the 'color'. This allows to align
pos.pieces() signatures with piece_list(), piece_count() and
all the other functions where 'color' argument is passed as
first one.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
It is more correct given what the function does. In
particular single_bit() returns true also in case of
empty bitboards.
Of course also the usual renaming while there :-)
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Shrinking from [16] to [2][2] is able to speedup
perft of start position of almost 5% !
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Also some microoptimizations, were there from ages
but hidden: the renaming suddendly made them visible!
This is a good example of how better naming lets you write
better code. Naming is really a kind of black art!
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
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 allows to retire ClearMaskBB[] and use just
one SquareBB[] array to set and clear a bit.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
They are almost the same, if the function arguments would
have been the same they could even be integrated.
Also a bit of renaming while there.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
Skip calling promotion generation functions in
the very common case of no possible promotion
evasion. Also retire generate_pawn_captures()
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
It should help to avoid recalculating check squares
of sliding attackers for queen when already done for
bishops and rooks. Of course this helps when there are
bishop, rook and queen on the board !
Fixed also a subtle bug (use of same variable b in while
condition and in condition body) introduced recently by
revision d655147e8c that triggers
in case we have at least 2 non-pawn discovered check pieces.
This is very rare that's why didn't show in the node count
verification where we actually have a case of 2 dc pieces
in position 14, but one is a pawn.
No functional change.
Signed-off-by: Marco Costalba <mcostalba@gmail.com>
