Don't take the split lock if we don't have
available slaves (about 30-40% of times).
This new condition allows to retire the now
redundant one on number of threads.
No functional change.
Split previous patch in 2 steps: first remove
the MOVE_NULL hack, then retire nullChild.
The first step is a prerequisite
for second one and affects bench.
The second step (next patch) just removes nullChild
without affecting bench.
bench: 8205159
Are broken for big-endian case and
I have verified with MSVC 2013 Premium
bench is correct and there is no
miscompilation, so the main reason
to change the original code drops.
No functional change.
Another attempt at retiring current asymmetric
king evaluation and use a much simpler symmetric
one. As a good side effect we can avoid recalculating
eval after a null move.
Tested in no-regression mode and passed
STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 21580 W: 3752 L: 3632 D: 14196
LTC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 18253 W: 2593 L: 2469 D: 13191
And a LTC regression test against SF DD to
verify we don't have regression against
weaker engines due to some kind of 'contempt'
effect:
ELO: 54.69 +-2.1 (95%) LOS: 100.0%
Total: 40000 W: 11072 L: 4827 D: 24101
bench: 8205159
Before it was working by accident in case of
see_sign() and failing with see() due to how
castle moves are coded (king captures the rook).
Better to explicitly filter out castling moves
and use see() without any surprise/trick.
No functional case.
Book handling belongs to GUI, we kept this code
for historical reasons, but nowdays there is
really no need of this old, (mostly) unused
and especially incorrect designed functionality.
It is up to the GUI to choose the book (far easier for
the user) and to select the book parameters. In no
place, including fishtest, TCEC, rating lists, etc.
the "own book" is used, moreover currently SF is
released without any book and even if in the future we
bundle a book in the release package, it will be the GUI
that will take care of it.
This corrects a wrong design decision that Galurung
and later Stockfish inherited from what was common
practice many yeas ago.
No functional change.
There is really little that user can achieve (apart
from a weakened engine) tweaking these parameters
that are already tuned and have no immediate or visible
effect.
So better do not expose them to the user and avoid the
typical "What is the best setup for my machine?" kind of
question (by far the most common, by far the most useless).
No functional change.
To show perft numbers for each move. Just
use 'divide' instead of 'perft', for instance:
position startpos moves e2e4 e7e5
divide 4
Inspired by Ronald de Man.
No functional change.
Retire current asymmetric king evaluation
and use a much simpler symmetric one.
As a side effect retire the infamous
'Aggressiveness' and 'Cowardice' UCI
options.
Tested in no-regression mode,
Passed both STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 33855 W: 5863 L: 5764 D: 22228
And LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 40571 W: 5852 L: 5760 D: 28959
bench: 8321835
At root we start counting plies from 1,
instead pv[] array starts from 0. So
the variable 'ply' we use in extract_pv_from_tt
to index pv[] is misnamed, indeed it is
not the real ply, but ply-1.
The fix is to leave ply name in extract_pv_from_tt
but assign it the correct start value and
consequentely change all the references to pv[].
Instead in insert_pv_in_tt it's simpler to rename
the misnamed 'ply' in 'idx'.
The off-by-one bug was unhidden when trying to use
'ply' for what it should have been, for instance in
this position:
position fen 8/6R1/8/3k4/8/8/8/2K5 w - - 0 1
at depth 24 mate line is erroneusly truncated due
to value_from_tt() using the wrong ply.
Spotted by Ronald de Man.
bench: 8732553
If razoring conditions are satisfied and
depth is low, then directly drop in qsearch.
Passed both STC
LLR: 2.98 (-2.94,2.94) [-1.50,4.50]
Total: 12914 W: 2345 L: 2208 D: 8361
And LTC
LLR: 2.95 (-2.94,2.94) [0.00,6.00]
Total: 50600 W: 7548 L: 7230 D: 35822
bench: 8739659
When there aren't legal moves after
a search, instead of returning imediately,
save bestValue in TT as in the usual case.
There is really no reason to special case
this one.
With this patch is fully fixed (again) follwing
position:
7k/6p1/6B1/5K1P/8/8/8/8 w - - 0 1
Also in SMP case.
bench: 8802105
After last Joona's patch there is no measurable
difference between the option set or unset.
Tested by Andreas Strangmüller with 16 threads
on his Dual Opteron 6376.
After 5000 games at 15+0.05 the result is:
1 Stockfish_14050822_T16_on : 3003 5000 (+849,=3396,-755), 50.9 %
2 Stockfish_14050822_T16_off : 2997 5000 (+755,=3396,-849), 49.1 %
bench: 880215
Instead of waiting to be allocated, actively search
for another split point to join when finishes its
search. Also modify split conditions.
This patch has been tested with 7 threads SMP and
passed both STC:
LLR: 2.97 (-2.94,2.94) [-1.50,4.50]
Total: 2885 W: 519 L: 410 D: 1956
And a reduced-LTC at 25+0.05
LLR: 2.95 (-2.94,2.94) [0.00,6.00]
Total: 4401 W: 684 L: 566 D: 3151
Was then retested against regression in 3 thread case
at standard LTC of 60+0.05:
LLR: 2.96 (-2.94,2.94) [-4.00,0.00]
Total: 40809 W: 5446 L: 5406 D: 29957
bench: 8802105
On a final fixed game number test it failed
to prove better than standard version.
STC 15+0.05
ELO: -0.86 +-1.7 (95%) LOS: 15.8%
Total: 57578 W: 10070 L: 10213 D: 37295
bench: 8802105
Unfortunatly we have a slow down that causes
a regression in STC with no-regression mode:
LLR: -2.96 (-2.94,2.94) [-3.00,1.00]
Total: 22454 W: 3836 L: 4029 D: 14589
bench: 8678654
The bug was found to be elsewhere. This version
is correct and also is able to detect as draw
positions like:
8/8/5b2/8/8/4k1p1/6P1/5K2 b - - 6 133
bench: 8678654
Position is win also if strong side has a bishop
and a knight (plus other material, otherwise
KBNK would be triggered instead of KXK).
This fixes a subtle bug where a search on position
k7/8/8/8/8/P7/PB6/K7 b - - 6 1
Instead of returning a draw score, suddendly returns
a big score. This happens because at one point in
search we reach this position:
8/Pk6/8/8/8/4B3/P7/K7 w - - 3 8
Where white can promote. In case of rook promotion (and also in case of
queen promotion) the resutling position gets a huge static eval that is
above VALUE_KNOWN_WIN (from the point of view of white). So for rook
promotion it is
&& futilityBase > -VALUE_KNOWN_WIN
that prevents futility pruning in qsearch. (Removing this condition indeed
lets the problem occur). Raising the static eval for K+B+N+X v K to a value
higher than VALUE_KNOWN_WIN fixes this particular problem without having to
introduce an extra futility pruning condition in qsearch.
I just checked and it seems K+R v K, K+2B v K and even K+B+N v K already get
a huge static eval. Why not K+B+N+P v K?
I think this fix corrects an oversight. There is special code for KBNK, but
KBNXK is handled by KXK, so the test for sufficient material should also test
for B+N.
bench: 8678654
In the (rare) cases when the two conditions
are true, then fully check again with a slow
but correct MoveList<LEGAL>(pos).size().
This is able to detect false positives like
this one:
8/8/8/Q7/5k1p/5P2/4KP2/8 b - - 0 17
When we have a possible simple pawn push that
is not stored in attacks[] array. Because the
third condition triggers very rarely, even if
it is slow, it does not alters in a measurable
way the average speed of the engine.
bench: 8678654
Currently a stealmate position is misevaluated
in a negative/positive score, this leads qsearch(),
that does not detects stealmates too, to return the
wrong score and this yields to some kind of endgames
to be completely misevaluated.
With this patch is fully fixed follwing position
7k/6p1/6B1/5K1P/8/8/8/8 w - - 0 1
Also in SMP case.
Correct root cause analysys by Ronald de Man.
bench: 8678654
After reverting to the original Tord's
endgame, a search on position
7k/6p1/6B1/5K1P/8/8/8/8 w - - 0 1
Reports, correctly, a draw score instead of
an advantage for white.
Issue reported by Uri Blass.
bench: 8678654
Remove the optimization for Intel, is not
standard and can break at any time, moreover
our release build is not done with Intel C++
anymore so we don't need to sqeeze the extra
speed out from this compiler.
No functional change.
If we return from split with a stale value
due to a stop or a cutoff upstream occurred,
then we exit moves loop and save a stale value
in TT before returning search().
This patch, from Joona, fixes this.
bench: 8678654
We can never have bestValue == -VALUE_INFINITE at
the end of move loop because if no legal move exists
we detect it with previous condition on !moveCount,
if a legal move exists we never prune it due to
futility pruning condition:
bestValue > VALUE_MATED_IN_MAX_PLY
So this code never executes, as I have also verified
directly.
Issue reported by Joona.
No functional change.
Intel compiler is very picky:
"error: this operation on an enumerated type requires an
applicable user-defined operator function"
Reported by Tony Gaor.
No functional change.
