As far as can tell, semiopenFiles are set if there is a pawn anywhere on
the file. The removed condition would be true even if the pawns were very
advanced, which doesn't make sense if we're looking for a trapped rook.
Seems the engine fairs better with this removed. My guess s that the
condition that mobility is 3 or less does this well enough.
Begs the question whether this is a mobility issue alone... not sure.
Should I do LTC test?
STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 13377 W: 3009 L: 2871 D: 7497
http://tests.stockfishchess.org/tests/view/5a855be40ebc590297cc8166
Passed LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 16288 W: 2813 L: 2685 D: 10790
http://tests.stockfishchess.org/tests/view/5a8575a80ebc590297cc817e
Bench: 5006365
Make contempt dependent on the current score of the root position.
The idea is that we now use a linear formula like the following to decide
on the contempt to use during a search :
contempt = x + y * eval
where x is the base contempt set by the user in the "Contempt" UCI option,
and y * eval is the dynamic part which adapts itself to the estimation of
the evaluation of the root position returned by the search. In this patch,
we use x = 18 centipawns by default, and the y * eval correction can go
from -20 centipawns if the root eval is less than -2.0 pawns, up to +20
centipawns when the root eval is more than 2.0 pawns.
To summarize, the new contempt goes from -0.02 to 0.38 pawns, depending if
Stockfish is losing or winning, with an average value of 0.18 pawns by default.
STC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 110052 W: 24614 L: 23938 D: 61500
http://tests.stockfishchess.org/tests/view/5a72e6020ebc590f2c86ea20
LTC:
LLR: 2.97 (-2.94,2.94) [0.00,5.00]
Total: 16470 W: 2896 L: 2705 D: 10869
http://tests.stockfishchess.org/tests/view/5a76c5b90ebc5902971a9830
A second match at LTC was organised against the current master:
ELO: 1.45 +-2.9 (95%) LOS: 84.0%
Total: 19369 W: 3350 L: 3269 D: 12750
http://tests.stockfishchess.org/tests/view/5a7acf980ebc5902971a9a2e
Finally, we checked that there is no apparent problem with multithreading,
despite the fact that some threads might have a slightly different contempt
level that the main thread.
Match of this version against master, both using 5 threads, time control 30+0.3:
ELO: 2.18 +-3.2 (95%) LOS: 90.8%
Total: 14840 W: 2502 L: 2409 D: 9929
http://tests.stockfishchess.org/tests/view/5a7bf3e80ebc5902971a9aa2
Include suggestions from Marco Costalba, Aram Tumanian, Ronald de Man, etc.
Bench: 5207156
The 'eval' debugging command in Terminal did not initialize the Eval::Contempt
variable, leading to random output during debugging sessions (normal search
was unaffected by the bug).
Example of session where the two 'eval' commands should give the same output,
but did not:
./stockfish
position startpos
d
eval
go depth 20
d
eval
The bug is fixed by initializing Eval::Contempt to SCORE_ZERO in Eval::trace
No functional change.
Current master can yield different staticEvals depending on the path
used to reach the position. The reason for this is that the evaluation after a
null move is always computed subtracting 2 * Eval::Tempo, while this is not
the case for lazy or specialized evals. This patch always adds tempo to evals,
which doesn't affect playing strength:
LTC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 59911 W: 7616 L: 7545 D: 44750
STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 104947 W: 18897 L: 18919 D: 67131
Fixes issue #1335
Bench: 5208264
Simplify the other check penalty computation. Compared to current master,
a) it uses a 143 kingDanger penalty instead of S(10, 10) for the "otherCheck"
(credits to ElbertoOne for finding a suitable kingDanger range to replace the score
and to Guardian for showing this could also be a neutral change at LTC).
This makes our king safety model more consistent and simpler.
b) it might also score more than one "otherCheck" penalty for a given piece type instead of just one
c) it might score many pinned penalties instead of just one.
d) It also remove 3 conditionals and uses simpler expressions.
So it was tested as a SPRT[-3, 1]
Passed STC
http://tests.stockfishchess.org/tests/view/5a2b560b0ebc590ccbb8ba6b
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 11705 W: 2217 L: 2080 D: 7408
And LTC
http://tests.stockfishchess.org/tests/view/5a2bfd0d0ebc590ccbb8bab0
LLR: 2.94 (-2.94,2.94) [-3.00,1.00]
Total: 26812 W: 3575 L: 3463 D: 19774
Trying to improve on b) another attempt was made to score also the
"otherchecks" for piece types which had some safe checks, but this
failed STC http://tests.stockfishchess.org/tests/view/5a2c79e60ebc590ccbb8badd
bench: 5149133
* A better contempt implementation for Stockfish
The round 2 of TCEC season 10 demonstrated the benefit of having a nice contempt implementation: it gives the strongest programs in the tournament the ability to slow down the game when they feel the position is slightly worse, prefering to stay in a complicated (even if slightly risky) middle game rather than simplifying by force into a drawn endgame.
The current contempt implementation of Stockfish is inadequate, and this patch is an attempt to provide a better one.
Passed STC non-regression test against master:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 83360 W: 15089 L: 15075 D: 53196
http://tests.stockfishchess.org/tests/view/5a1bf2de0ebc590ccbb8b370
This contempt implementation is showing promising results in certains situations. For instance, it obtained a nice +30 Elo gain when playing with contempt=40 against Stockfish 7, compared to current master:
• master against SF 7 (20000 games at LTC): +121.2 Elo
• this patch with contempt=40 (20000 games at LTC): +154.11 Elo
This was the result of real cooperative work from the Stockfish team, with key ideas coming from Stefan Geschwentner (locutus2) and Chris Cain (ceebo) while most of the community helped with feedback and computer time.
In this commit the bench is unchanged by default, but you can test at home with the new contempt in the UCI options. The style of play will change a lot when using contempt different of zero (I repeat: not done in this version by default, however)!
The Stockfish team is still deliberating over the best default contempt value in self-play and the best contempt modeling strategy, to help users choosing a contempt value when playing against much weaker programs. These informations will be given in future commits when available :-)
Bench: 5051254
* Remove the prefetch
No functional change.
Currently the NORTH/WEST/SOUTH/EAST values are of type Square, but conceptually they are not squares but directions. This patch separates these values into a Direction enum and overloads addition and subtraction to allow adding a Square to a Direction (to get a new Square).
I have also slightly trimmed the possible overloadings to improve type safety. For example, it would normally not make sense to add a Color to a Color or a Piece to a Piece, or to multiply or divide them by an integer. It would also normally not make sense to add a Square to a Square.
This is a non-functional change.
The new "weak" expression helps simplify the safe check calculations for rooks or minors, (but the end result for all the safe checks is the exactly the same as in current master)
The only functional change is for the "outer king ring" (for example, squares f3 g3 h3 when white king is on g1). In current master, there was a 191 penalty if any of these was not defended at all.
With this pr, there is this 191 penalty if any of these is not defended at all or is only defended by a white queen.
Tested as a simplification
STC
http://tests.stockfishchess.org/tests/view/59fb03d80ebc590ccbb89fee
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 66167 W: 12015 L: 11971 D: 42181
(against master (Update Copyright year inMakefile))
LTC
http://tests.stockfishchess.org/tests/view/5a0106ae0ebc590ccbb8a55f
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 15790 W: 2095 L: 1968 D: 11727
(against master (Handle BxN trade as good capture when history scor))
same as #1296 but rebased on latest master
bench: 5109559
Avoid constructing, passing as a parameter and binding a useless empty tuple of pointers in the qsearch move picker constructor.
Also reformat the scoring function in movepicker.cpp and do some cleaning in evaluate.cpp while there.
No functional change.
This patch puts the evaluation helper functions inside EvalInfo struct, which simplifies a bit their signature and (most importantly, IMHO) makes their C++ code much cleaner and simpler to read (by removing the "ei." qualifiers all around in evaluate.cpp).
Also rename the EvalInfo struct into Evaluation class to get a natural invocation v = Evaluation(p).value() to evaluation position p.
The downside is an increase of 20 lines in evaluate.cpp (for the prototypes of the helper functions). The upsides are better readability and a speed-up of 0.6% (by generating all the helpers for the NO_TRACE case together, which helps the instruction cache).
No functional change
Closes#1135
The previous patch has added a fraction of the king danger score to the
endgame score of the tapered eval, so it seems natural to perform the
king danger computation later in the endgame.
With this patch we extend the limit of such check analysis down to the
material of Rook+Knight, when we have at least two pieces attacking the
opponent king zone.
Passed STC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 7446 W: 1409 L: 1253 D: 4784
http://tests.stockfishchess.org/tests/view/591c097c0ebc59035df3477c
and LTC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 14234 W: 1946 L: 1781 D: 10507
http://tests.stockfishchess.org/tests/view/591c24f10ebc59035df3478c
Bench: 5975183
Closes#1121
In current master the size of the king ring varies abruptly from eight
squares when the king is in g8, to 12 squares when it is in g7. Because
the king ring is used for estimating attack strength, this may lead to
an overestimation of king danger in some positions. This patch limits
the king ring to eight squares in all cases.
Inspired by the following forum thread:
https://groups.google.com/forum/?fromgroups=#!topic/fishcooking/xrUCQ7b0ObE
Passed STC:
LLR: 2.97 (-2.94,2.94) [0.00,5.00]
Total: 9244 W: 1777 L: 1611 D: 5856
and LTC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 87121 W: 11765 L: 11358 D: 63998
Bench: 6121121
Closes#1115
Replacing the old Protector table with a simple linear formula which takes into account a different slope for each different piece type.
The idea of this simplification of Protector is originated by Alain (Rocky)
STC: LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 70382 W: 12859 L: 12823 D: 44700
LTC: LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 61554 W: 8098 L: 8031 D: 45425
Bench: 6107863
Closes#1099
STC
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 58462 W: 10615 L: 10558 D: 37289
LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 65061 W: 8539 L: 8477 D: 48045
It is worth noting that an attempt to only increase the bonus passed STC but failed LTC, and
an attempt to remove the cap without increasing the bonus is still running at STC, but will probably fail after more than 100k.
Bench: 6188591
Closes#1063
This patch removes the empty rows at the beginning and at the end of
MobilityBonus[] and Protector[] arrays:
• reducing the size of MobilityBonus from 768 bytes to 512 bytes
• reducing the size of Protector from 1024 to 512 bytes
Also adds some comments and cleaner code for the arrays in pawns.cpp
No speed penalty (measured speed-up of 0.4%).
No functional change.
Closes#1018
By defining "strongly protected" as "protected by a pawn, or protected
by two pieces and not attacked by two enemy pieces".
Passed STC:
LLR: 2.97 (-2.94,2.94) [0.00,5.00]
Total: 17050 W: 3128 L: 2931 D: 10991
Passed LTC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 120995 W: 15852 L: 15343 D: 89800
Bench : 6269229
Closes#1016
Initial protective idea by Snicolet for knight, for other pieces too
Patch add penalties and bonuses for pieces, depending on the distance from the own king
STC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 21192 W: 3919 L: 3704 D: 13569
LTC:
LLR: 2.96 (-2.94,2.94) [0.00,5.00]
Total: 26177 W: 3642 L: 3435 D: 19100
Bench : 6687377
Closes#1012
Positions with pawns on only one flank tend to be more drawish. We add
a term to the initiative bonus to help the attacking player keep pawns
on both flanks.
STC: yellowish run stopped after 257137 games
LLR: -0.92 (-2.94,2.94) [0.00,5.00]
Total: 257137 W: 46560 L: 45511 D: 165066
LTC:
LLR: 2.95 (-2.94,2.94) [0.00,5.00]
Total: 15602 W: 2125 L: 1956 D: 11521
Bench : 6976310
Closes#1009
