Collect and give a second try to some almost passed tuning attempts and
one-line tweaks from the last month.
Passed STC
LLR: 3.07 (-2.94,2.94) [0.00,4.00]
Total: 15124 W: 2974 L: 2756 D: 9394
And LTC
LLR: 2.95 (-2.94,2.94) [0.00,4.00]
Total: 21577 W: 3507 L: 3289 D: 14781
Bench: 8855226
Resolves#464
Coverity scan warns about uninitialized 'sf' argument when
calling probe(). Actually it is a false positive because
argument is passed by reference and assigned inside
probe(). Nevertheless it is a hint that fucntion signature
is a bit tricky, so rewrite it in a more conventional way,
assigning 'sf' from probe() return value.
No functional change.
Import C++11 branch from:
https://github.com/mcostalba/Stockfish/tree/c++11
The version imported is teh last one as of today:
6670e93e50
Branch is fully equivalent with master but syzygy
tablebases that are missing (but will be added with
next commit).
bench: 8080602
It is up to material (and pawn) table look up
code to know where the per-thread tables are,
so change API to reflect this.
Also some comment fixing while there
No functional change.
Move all in evaluation.
Simplify the code and concentrate in a single place
all the logic behind space evaluation, making it much
more clear.
Verified also at STC it does not regress due to a possible
slow down:
LLR: 3.91 (-2.94,2.94) [-3.00,1.00]
Total: 65744 W: 13285 L: 13194 D: 39265
No functional change.
Currently king has no material key associated because
it can never happen to find a legal position without
both kings, so there is no need to keep track of it.
The consequence is that a position with only the two
kings has material key set at zero and if the material
hash table is empty any entry will match and this is
wrong.
Normally bug is hidden becuase the checking for a draw
with pos.is_draw() is done earlier than evaluate() call,
so that we never check in gameplay the material key of a
position with two kings.
Nevertheless the bug is there and can be reproduced setting
at startup a position with only two kings and typing
'eval' from prompt.
The fix is very simple: add a random key also for the king.
Also fixed the condition in material.cpp to avoid asserting
when a 'just 2 kings' postion is evaluated.
No functional change.
Retire KmmKm evaluation function. Instead give a very drawish
scale factor when the material advantage is small and not much
material remains.
Retire NoPawnsSF array. Pawnless endgames without a bishop will
now be scored higher. Pawnless endgames with a bishop pair will
be scored lower. The effect of this is hopefully small.
Consistent results both at short TC (fixed games):
ELO: -0.00 +-2.1 (95%) LOS: 50.0%
Total: 40000 W: 7405 L: 7405 D: 25190
And long TC (fixed games):
ELO: 0.77 +-1.9 (95%) LOS: 78.7%
Total: 39690 W: 6179 L: 6091 D: 27420
bench: 7213723
But compensate by reducing rook and queen
value by 53 = (160 / 3)
Material imbalances are affected as follows:
Red. Major Rook Queen Total
QRR +160 -2*53 -53 +1
QR +160 -53 -53 +54
RR +160 -2*53 0 +54
R 0 -53 0 -53
Q 0 0 -53 -53
so that the imbalance changes by at most 54 + 53 = 107 units.
This corresponds to appromximately 3.5cp in the final evaluation.
Verified with fixed number 40000 games at both short
and long TC it does not regress.
Short TC 15+0.05
ELO: 1.93 +-2.1 (95%) LOS: 96.6%
Total: 40000 W: 7520 L: 7298 D: 25182
Long TC 60+0.05
ELO: -0.33 +-1.9 (95%) LOS: 36.5%
Total: 39663 W: 6067 L: 6105 D: 27491
bench: 6703846
RedundantRook and RedundantQueen replaced by simple
variable RedundantMajor. Also the SameColor coefficient
for Queen<->Queen has been set by definition to 0.
The remaining 5 parameters:
LinearCoefficients[ROOK]
LinearCoefficients[QUEEN]
QuadraticCoefficientsSameColor[ROOK][ROOK]
QuadraticCoefficientsSameColor[QUEEN][ROOK]
RedundantMajor
are sufficient to equate the material imbalances for the
5 common material configurations of R, RR, Q, QR and QRR
to any desired values simultaneously.
With the chosen parameters there should be no functional
change unless one side has more than 2 rooks or more
than 1 queen. For example bench from the start position
using the commands:
./stockfish
go depth 16
produces identical output except for one extra node
in the last iteration.
bench: 8198094
Coefficients for Bishop<->BishopPair and Bishop<->Bishop
are also pretty much redundant. By altering the values
in LinearCoefficients[] these coefficients can be zeroed
without changing the imbalance calculations in any position
with less than 3 bishops for one side.
bench: 7995098
First coefficient in the SameColor array does an
equivalent job when folded into the LinearCoefficients
array.
All of the diagonal terms in the OppositeColor array
are redundant due to cancellation.
No functional change.
A combo of two patches that failed SPRT with score
higher than 50% but togheter they succeed:
SPRT at 60+0.05
LLR: 2.95 (-2.94,2.94) [0.00,6.00]
Total: 7312 W: 1276 L: 1139 D: 4897
bench: 8029334
Idea is sound but implementation is partial. Ryan and Joona noticed that
we leave an hole in material table. Also we got another report by an user
of an odd behaviour. Namely, if you start stockfish and from the prompt
give 'bench' you get 3453941, then if you run again bench you get 3453940.
The reason is that two different positions with the same number of pieces,
but one with a bishop pair and another without have the same material key.
But after Eelco patch also different material imbalance and this yields
to this issue.
Restesting at long TC shows the patch does not really contribute at
ELO improvement. Actually patch failed at long TC.
LLR: -2.97 (-2.94,2.94)
Total: 23109 W: 4104 L: 4092 D: 14913
So revert.
bench: 3453945
Prefer pos.bishop_pair() to pos.count<BISHOP>(WHITE) > 1
because the first checks that the two bishops are on
different color squares.
Although the change seems to kick in only in very rare cases,
quite surprisingly it was able to pass SPRT test at short TC.
LLR: 2.95 (-2.94,2.94)
Total: 39818 W: 8174 L: 7956 D: 23688
bench: 3453941
The case of two lone kings on the board is already considered
by the "No pawns" scaling factor rules in material.cpp as is
KBK and KNK.
Moreover we had a small leak in endgames map because for
KK endgame it happens white and black material keys are the
same (both equal to zero), so when adding the black endgame in
Endgames::add() we were overwriting the already exsisting
white one, leading to a memory leak found by Valgrind.
So remove the endgames althogheter and rely on scaling
to correctly set the endgames value to a draw.
No functional change.
