In a recent commit, "Introduce king flank defenders," a term was introduced
by Michael Chaly (@Vizvezdenec) to reduce king danger based on king defenders,
i.e., friendly attacks on our King Flank and Camp. This is a powerful idea
and broadly applicable to all of our pieces.
An earlier, but narrower, version of a similar idea was already coded into
king danger, with a term reducing king danger simply if we had a bishop and
king attacking the same square -- there is also a similar term for knights,
but roughly three times larger. I had attempted to tweak this term's coefficient
fairly recently, in a series of tests in early September which increased this
coefficient. All failed STC with significantly negative scores.
Now that the king flank defenders term has been introduced, it appears that
the bishop-defense term can be simplified away without compensation or
significant Elo loss.
Where do we go from here? This PR is a natural follow-up to "Introduce king
flank defenders," which proposed simplification with existing and overlapping
terms, such as this one. That PR also mentioned that the coefficient it
introduced appeared arbitrary, so perhaps this PR can facilitate a tweak to
increase king flank defenders' coefficient.
Additionally, this pull request is extremely similar to https://github.com/official-stockfish/Stockfish/pull/1821,
which was (coincidentally) merged a year ago, to the day (November 23, 2018).
That patch also simplified away a linear king danger tropism term, which was
soon after replaced with a quadratic term by @Vizvezdenec (which would not have
passed without the simplification). @Vizvezdenec, again by coincidence, has
recently been trying to implement a quadratic term, this time for defenders
rather than attackers. This history of this evaluation code suggests that
this simplification might be enough to help a patch for quadratic king-flank
defenders pass.
Bench: 4959670
STC:
LLR: 2.94 (-2.94,2.94) [-3.00,1.00]
Total: 22209 W: 4920 L: 4800 D: 12489
https://tests.stockfishchess.org/tests/view/5dd444d914339111b9b6bed7
LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 152107 W: 24658 L: 24743 D: 102706
https://tests.stockfishchess.org/tests/view/5dd4be31f531e81cf278ea9d
Interesting discussion on Github about this pull request:
https://github.com/official-stockfish/Stockfish/pull/2424
---
This pull request was opened less than one week before the holiday of
Thanksgiving here in the United States. In keeping with the holiday
tradition of expressing gratitude, I would like to thank our generous
CPU donors, talented forum contributors, innovative developers, speedy
fishtest approvers, and especially our hardworking server maintainers
(@ppigazzini and @tomtor). Thank you all for a year of great Stockfish
progress!
This patch measures how frequently search is exploring new configurations.
This is done be computing a running average of ttHit. The ttHitAverage rate
is somewhat low (e.g. 30% for startpos) in the normal case, while it can be
very high if no progress is made (e.g. 90% for the fortress I used for testing).
This information can be used to influence search. In this patch, by adjusting
reductions if the rate > 50%. A first version (using a low ttHitAverageResolution
and this 50% threshold) passed testing:
STC
LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 26425 W: 5837 L: 5650 D: 14938
http://tests.stockfishchess.org/tests/view/5dcede8b0ebc5902563258fa
LTC
LLR: 2.96 (-2.94,2.94) [0.00,3.50]
Total: 32313 W: 5392 L: 5128 D: 21793
http://tests.stockfishchess.org/tests/view/5dcefb1f0ebc590256325c0e
However, as discussed in pull request 2414, using a larger ttHitAverageResolution
gives a better approximation of the underlying distributions. This needs a slight
adjustment for the threshold as the new distributions are shifted a bit compared
to the older ones, and this threshold seemingly is sensitive (we used 0.53125 here).
https://github.com/official-stockfish/Stockfish/pull/2414
This final version also passed testing, and is used for the patch:
STC
LLR: 2.95 (-2.94,2.94) [-1.50,4.50]
Total: 16025 W: 3555 L: 3399 D: 9071
http://tests.stockfishchess.org/tests/view/5dd070b90ebc5902579e20c2
LTC
LLR: 2.96 (-2.94,2.94) [0.00,3.50]
Total: 37576 W: 6277 L: 5998 D: 25301
http://tests.stockfishchess.org/tests/view/5dd0f58e6f544e798086f224
Closes https://github.com/official-stockfish/Stockfish/pull/2414
Bench: 4989584
This patch implements what we have been trying for quite some time -
dependance of kingdanger on balance of attackers and defenders of king
flank, to avoid overestimate attacking power if the opponent has enough
defenders of king position. We already have some form of it in bishop
and knight defenders - this is further work in this direction.
What to do based on this?
1) constant 4 is arbitrary, maybe it is not optimal
2) maybe we can use quadratic formula as in kingflankattack
3) simplification into alrealy existing terms is always a possibility :)
4) overall kingdanger tuning always can be done.
passed STC:
http://tests.stockfishchess.org/tests/view/5dcf40560ebc590256325f30
LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 26298 W: 5819 L: 5632 D: 14847
passed LTC:
http://tests.stockfishchess.org/tests/view/5dcfa5760ebc590256326464
LLR: 2.96 (-2.94,2.94) [0.00,3.50]
Total: 30600 W: 5042 L: 4784 D: 20774
Closes https://github.com/official-stockfish/Stockfish/pull/2415
Bench: 4496847
Introduce OutpostRank[RANK_NB] which contains a bonus according to
the rank of the outpost. We use it for the primary Outpost bonus.
The values are based on the trends of the SPSA tuning run with some
manual tweaks.
Passed STC:
LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 27454 W: 6059 L: 5869 D: 15526
http://tests.stockfishchess.org/tests/view/5dcadba20ebc590256922f09
Passed LTC:
LLR: 2.94 (-2.94,2.94) [0.00,3.50]
Total: 57950 W: 9443 L: 9112 D: 39395
http://tests.stockfishchess.org/tests/view/5dcaea880ebc5902569230bc
Bench: 4778405
----------------------------
The inspiration for this patch came from Stefan Geschwentner's attempt
of modifying BishopPawns into a rank-based penalty. Michael Stembera
suggested that maybe the S(0, 0) ranks (3rd, 7th and also maybe 8th)
can still be tuned. This would expand our definition of Outpost and
OutpostRanks would be removed altogether. Special thanks to Mark Tenzer
for all the help and excellent suggestions.
The removed lines approximately duplicate equivalent logic in the movePicker.
Adjust the futility_move_count to componsate for some difference
(the movePicker prunes one iteration of the move loop later).
Passed STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 8114 W: 1810 L: 1663 D: 4641
http://tests.stockfishchess.org/tests/view/5dc6afe60ebc5902562bd318
Passed LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 89956 W: 14473 L: 14460 D: 61023
http://tests.stockfishchess.org/tests/view/5dc6bdcf0ebc5902562bd3c0
Closes https://github.com/official-stockfish/Stockfish/pull/2407
Bench: 4256440
---------------------
How to continue from there?
It would be interesting to see if we can extract some Elo gain
from the new futility_move_count formula, for instance by somehow
incorporating the final -1 in the 5 constant, or adding a linear
term to the quadratics...
```
futility_move_count = (5 + depth * depth) * (1 + improving) / 2 - 1
```
Current master 648c7ec25d will generate an
incorrect mate score for:
```
setoption name Hash value 8
setoption name Threads value 1
position fen 8/1p2KP2/1p4q1/1Pp5/2P5/N1Pp1k2/3P4/1N6 b - - 76 40
go depth 49
```
even though the position is a draw. Generally, SF tries to display only
proven mate scores, so this is a bug.
This was posted http://www.talkchess.com/forum3/viewtopic.php?f=2&t=72166
by Uri Blass, with the correct analysis that this must be related to the
50 moves draw rule being ignored somewhere.
Indeed, this is possible as positions and there eval are stored in the TT,
without reference to the 50mr counter. Depending on the search path followed
a position can thus be mate or draw in the TT (GHI or Graph history interaction).
Therefore, to prove mate lines, the TT content has to be used with care. Rather
than ignoring TT content in general or for mate scores (which impact search or
mate finding), it is possible to be more selective. In particular, @WOnder93
suggested to only ignore the TT if the 50mr draw ply is closer than the mate
ply. This patch implements this idea, by clamping the eval in the TT to
+-VALUE_MATED_IN_MAX_PLY. This retains the TTmove, but causes a research of
these lines (with the current 50mr counter) as needed.
This patch hardly ever affects search (as indicated by the unchanged
bench), but fixes the testcase. As the conditions are very specific,
also mate finding will almost never be less efficient (testing welcome).
It was also shown to pass STC and LTC non-regression testing, in a form
using if/then/else instead of ternary operators:
STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 93605 W: 15346 L: 15340 D: 62919
http://tests.stockfishchess.org/tests/view/5db45bb00ebc5908127538d4
LTC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 33873 W: 7359 L: 7261 D: 19253
http://tests.stockfishchess.org/tests/view/5db4c8940ebc5902d6b146fc
closes https://github.com/official-stockfish/Stockfish/issues/2370
Bench: 4362323
This reverts the previous commit. The PSQT changes in this previous
commit originated from tests against quite an old version of master
which did not include the other PSQT changes of 474d133 for the other
pieces, and there might be some unknown interactions between the PSQT
tables. So we made a non-regression test of the last commit against the
last-but-one commit. This test failed, leading to the revert decision.
Failed non-regression test:
LLR: -2.96 (-2.94,2.94) [-3.00,1.00]
Total: 95536 W: 15047 L: 15347 D: 65142
http://tests.stockfishchess.org/tests/view/5dc0ba1d0ebc5904493b0112
Closes https://github.com/official-stockfish/Stockfish/pull/2395
Bench: 4362323
As Stockfish developers, we aim to make our code as legible and as close
to simple English as possible. However, one of the more notable exceptions
to this rule concerns operations between Squares and Bitboards.
Prior to this pull request, AND, OR, and XOR were only defined when the
Bitboard was the first operand, and the Square the second. For example,
for a Bitboard b and Square s, "b & s" would be valid but "s & b" would not.
This conflicts with natural reasoning about logical operators, both
mathematically and intuitively, which says that logical operators should
commute.
More dangerously, however, both Square and Bitboard are defined as integers
"under the hood." As a result, code like "s & b" would still compile and give
reasonable bench values. This trap occasionally ensnares even experienced
Stockfish developers, but it is especially dangerous for new developers not
aware of this peculiarity. Because there is no compilation or runtime error,
and a reasonable bench, only a close review by approvers can spot this error
when a test has been submitted--and many times, these bugs have slipped past
review. This is by far the most common logical error on Fishtest, and has
wasted uncountable STC games over the years.
However, it can be fixed by adding three non-functional lines of code. In this
patch, we define the operators when the operands are provided in the opposite
order, i.e., we make AND, OR, and XOR commutative for Bitboards and Squares.
Because these are inline methods and implemented identically, the executable
does not change at all.
This patch has the small side-effect of requiring Squares to be explicitly
cast to integers before AND, OR, or XOR with integers. This is only performed
twice in Stockfish's source code, and again does not change the executable at
all (since Square is an enum defined as an integer anyway).
For demonstration purposes, this pull request also inverts the order of one AND
and one OR, to show that neither the bench nor the executable change. (This
change can be removed before merging, if preferred.)
I hope that this pull request significantly lowers the barrier-of-entry for new
developer to join the Stockfish project. I also hope that this change will improve
our efficiency in using our generous CPU donors' machines, since it will remove
one of the most common causes of buggy tests.
Following helpful review and comments by Michael Stembera (@mstembera), we add
a further clean-up by implementing OR for two Squares, to anticipate additional
traps developers may encounter and handle them cleanly.
Closes https://github.com/official-stockfish/Stockfish/pull/2387
No functional change.
Simplify the king ring initialization and make it more regular, by just
moving the king square off the edges and using PseudoAttacks by king from
this new square.
There is a small functional difference from the previous master, as the
old master excludes the original ksq square while this patch always includes
the nine squares block (after moving the king from the edges). Additionally,
master does not adjust the kingRing down if we are on relative rank 8,
while this patch treats all of the edges the same.
STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 13263 W: 2968 L: 2830 D: 7465
http://tests.stockfishchess.org/tests/view/5db872830ebc5902d1f388aa
LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 72996 W: 11819 L: 11780 D: 49397
http://tests.stockfishchess.org/tests/view/5db899c20ebc5902d1f38b5e
Closes https://github.com/official-stockfish/Stockfish/pull/2384
Bench: 4959244
Make dynamic contempt weight factor dependent on static contempt so that higher
static contempt implies less dynamic contempt and vice versa. For default contempt
24 this is a non-functional change. But tests with contempt 0 shows an elo gain.
Also today is my birthday so i have already give to myself a gift with this patch :-)!
Further proceedings:
in the past we checked for default contempt that it doesn't regress against
contempt 0. Now that the later is stronger and the former is the same strength
this should be rechecked. Perhaps the default contempt have to be lowered.
It would be interesting to get some idea of the impact of this patch outside
of the 0-24 contempt range.
STC: (both with contempt=0)
LLR: 2.95 (-2.94,2.94) [-1.50,4.50]
Total: 21912 W: 3898 L: 3740 D: 14274
http://tests.stockfishchess.org/tests/view/5db74b6f0ebc5902d1f37405
LTC: (both with contempt=0)
LLR: 2.96 (-2.94,2.94) [0.00,3.50]
Total: 27172 W: 3350 L: 3126 D: 20696
http://tests.stockfishchess.org/tests/view/5db760020ebc5902d1f375d0
Closes https://github.com/official-stockfish/Stockfish/pull/2382
No functional change (for current default contempt 24).
This PR refactors update_quiet_stats, update_capture_stats and search to more clearly reflect what is actually done.
Effectively, all stat updates that need to be done after search is finished and a bestmove is found,
are collected in a new function ```final_stats_update()```. This shortens our main search routine, and simplifies ```update_quiet_stats```.
The latter function is now more easily reusable with fewer arguments, as the handling of ```quietsSearched``` is only needed in ```final_stats_update```.
```update_capture_stats```, which was only called once is now integrated in ```final_stats_update```, which allows for removing a branch and reusing some ```stat_bonus``` calls. The need for refactoring was also suggested by the fact that the comments of ```update_quiet_stats``` and ```update_capture_stats``` were incorrect (e.g. ```update_capture_stats``` was called, correctly, also when the bestmove was a quiet and not a capture).
passed non-regression STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 75196 W: 16364 L: 16347 D: 42485
http://tests.stockfishchess.org/tests/view/5db004ec0ebc5902c06db9e1
The diff is most easily readable as ```git diff master --patience```
No functional change
- Cleanups by Alain
- Group king attacks and king defenses
- Signature of futility_move_count()
- Use is_discovery_check_on_king()
- Simplify backward definition
- Use static asserts in move generator
- Factor a statement in move generator
No functional change
Stockfish crashes immediately if users enter a wrong file name (or even an existing
folder name) for debug log file. It may be hard for users to find out since it prints
nothing. If they enter the string via a chess GUI, the chess GUI may remember and
auto-send to Stockfish next time, makes Stockfish crashes all the time. Bug report by
Nguyen Hong Pham in this issue: https://github.com/official-stockfish/Stockfish/issues/2365
This patch avoids the crash and instead prefers to exit gracefully with a error
message on std:cerr, like we do with the fenFile for instance.
Closes https://github.com/official-stockfish/Stockfish/pull/2366
No functional change.
With the current questions and issues around threading, I had a look at
https://github.com/official-stockfish/Stockfish/issues/2299.
It seems there was a problem with data races when requesting eval via UCI while
a search was already running. To fix this an extra thread uithread was created,
presumably to avoid an overlap with Threads.main() that was causing problems.
Making this eval request seems to be outside the scope of UCI, and @vondele also
reports that the data race is not even fixed reliably by this change. I suggest
we simplify the threading here by removing this uithread and adding a comment
signaling that user should not request eval when a search is already running.
Closes https://github.com/official-stockfish/Stockfish/pull/2310
No functional change.
The current bench is missing a position with high 50 moves rule counter,
making most 'shuffle' tests based on 50mr > N seem non-functional.
This patch adds one FEN with high 50mr counter to address this issue
(taken from a recent tcec game).
Four new FENs:
- position with high 50mr counter
- tactical position with many captures, checks, extensions, fails high/low
- two losses by Stockfish in the S16 bonus games against Houdini
See the pull request for nice comments by @Alayan-stk-2 about each position
in bench: https://github.com/official-stockfish/Stockfish/pull/2338
Bench: 4590210
Previously, we used various control statements and ternary operators to divide
Outpost into four bonuses, based on whether the outpost was for a knight or
bishop, and whether it was currently an Outpost or merely a potential ("reachable")
one in the future. Bishop outposts, however, have traditionally been worth far
less Elo in testing. An attempt to remove them altogether passed STC, but failed LTC.
Here we include a narrower simplification, removing the reachable Outpost bonus
for bishops. This bonus was always suspect, given that its current implementation
conflicts directly with BishopPawns. BishopPawns penalizes our bishops based on the
number of friendly pawns on the same color of square, but by definition, Outposts
must be pawn-protected! This PR helps to alleviate this conceptual contradiction
without loss of Elo and with slightly simpler code.
On a code level, this allows us to simplify a ternary operator into the previous
"if" block and distribute a multiplication into an existing constant Score. On a
conceptual level, we retire one of the four traditional Outpost bonuses.
STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 22277 W: 4882 L: 4762 D: 12633
http://tests.stockfishchess.org/tests/view/5d9aeed60ebc5902b6cf9751
LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 51206 W: 8353 L: 8280 D: 34573
http://tests.stockfishchess.org/tests/view/5d9af1940ebc5902b6cf9cd5
Closes https://github.com/official-stockfish/Stockfish/pull/2352
Bench: 3941591
This patch changes the base aspiration window size depending on the absolute
value of the previous iteration score, increasing it away from zero. This
stems from the observation that the further away from zero, the more likely
the evaluation is to change significantly with more depth. Conversely, a
tighter aspiration window is more efficient when close to zero.
A beneficial side-effect is that analysis of won positions without a quick
mate is less prone to waste nodes in repeated fail-high that change the eval
by tiny steps.
STC:
LLR: 2.96 (-2.94,2.94) [0.50,4.50]
Total: 60102 W: 13327 L: 12868 D: 33907
http://tests.stockfishchess.org/tests/view/5d9a70d40ebc5902b6cf39ba
LTC:
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 155553 W: 25745 L: 25141 D: 104667
http://tests.stockfishchess.org/tests/view/5d9a7ca30ebc5902b6cf4028
Future work : the values used in this patch were only a reasonable guess.
Further testing should unveil more optimal values. However, the aspiration
window is rather tight with a minimum of 21 internal units, so discrete
integers put a practical limitation to such tweaking.
More exotic experiments around the aspiration window parameters could also
be tried, but efficient conditions to adjust the base aspiration window size
or allow it to not be centered on the current evaluation are not obvious.
The aspiration window increases after a fail-high or a fail-low is another
avenue to explore for potential enhancements.
Bench: 4043748
Run as a simplification
a) insures that pawn attacks are always included in the pawn span
(this "fixes" the case where some outpost or reachable outpost
bonus were awarded on squares controlled by enemy pawns).
b) compute the full span only if not "backward" or not "blocked".
By looking at "blocked" instead of "opposed", we get a nice simpli-
fication and the "new" outpost detection is almost identical, except
a few borderline cases on rank 4.
passed STC
http://tests.stockfishchess.org/tests/view/5d9950730ebc5902b6cefb90
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 79113 W: 17168 L: 17159 D: 44786
passed LTC
http://tests.stockfishchess.org/tests/view/5d99d14e0ebc5902b6cf0692
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 41286 W: 6819 L: 6731 D: 27736
See https://github.com/official-stockfish/Stockfish/pull/2348
bench: 3812891
It is always used as a bool, so let's make it a bool straight away.
We can always redefine it as a Piece in a later patch if we want
to use the piece type or the piece color.
No functional change.
Simplification that eliminates ONE_PLY, based on a suggestion in the forum that
support for fractional plies has never been used, and @mcostalba's openness to
the idea of eliminating it. We lose a little bit of type safety by making Depth
an integer, but in return we simplify the code in search.cpp quite significantly.
No functional change
------------------------------------------
The argument favoring eliminating ONE_PLY:
* The term “ONE_PLY” comes up in a lot of forum posts (474 to date)
https://groups.google.com/forum/?fromgroups=#!searchin/fishcooking/ONE_PLY%7Csort:relevance
* There is occasionally a commit that breaks invariance of the code
with respect to ONE_PLY
https://groups.google.com/forum/?fromgroups=#!searchin/fishcooking/ONE_PLY%7Csort:date/fishcooking/ZIPdYj6k0fk/KdNGcPWeBgAJ
* To prevent such commits, there is a Travis CI hack that doubles ONE_PLY
and rechecks bench
* Sustaining ONE_PLY has, alas, not resulted in any improvements to the
engine, despite many individuals testing many experiments over 5 years.
The strongest argument in favor of preserving ONE_PLY comes from @locutus:
“If we use par example ONE_PLY=256 the parameter space is increases by the
factor 256. So it seems very unlikely that the optimal setting is in the
subspace of ONE_PLY=1.”
There is a strong theoretical impediment to fractional depth systems: the
transposition table uses depth to determine when a stored result is good
enough to supply an answer for a current search. If you have fractional
depths, then different pathways to the position can be at fractionally
different depths.
In the end, there are three separate times when a proposal to remove ONE_PLY
was defeated by the suggestion to “give it a few more months.” So… it seems
like time to remove this distraction from the community.
See the pull request here:
https://github.com/official-stockfish/Stockfish/pull/2289
Remove temporary array of shelters and avoid iterating over it each time to find
if the shelter values after castling are better than the current value.
Work done on top of https://github.com/official-stockfish/Stockfish/pull/2277
Speed benchmark did not measure any difference.
No functional change
In lazySMP it makes sense to prune a little more, as multiple threads
search wider. We thus increase the prefactor of the reductions slowly
as a function of the threads. The prefactor of the log(threads) term
is a parameter, this pull request uses 1/2 after testing.
passed STC @ 8threads:
LLR: 2.96 (-2.94,2.94) [0.50,4.50]
Total: 118125 W: 23151 L: 22462 D: 72512
http://tests.stockfishchess.org/tests/view/5d8bbf4d0ebc59509180f217
passed LTC @ 8threads:
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 67546 W: 10630 L: 10279 D: 46637
http://tests.stockfishchess.org/tests/view/5d8c463b0ebc5950918167e8
passed ~LTC @ 14threads:
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 74271 W: 12421 L: 12040 D: 49810
http://tests.stockfishchess.org/tests/view/5d8db1f50ebc590f3beb24ef
Note:
A larger prefactor (1) passed similar tests at STC and LTC (8 threads),
while a very large one (2) passed STC quickly but failed LTC (8 threads).
For the single-threaded case there is no functional change.
Closes https://github.com/official-stockfish/Stockfish/pull/2337
Bench: 4088701
Fixup: remove redundant code.
A curious feature of Stockfish's current extension code is its repeated
use of "else if." In most cases, this makes no functional difference,
because no more than one extension is applied; once one extension has
been applied, the remaining ones can be safely ignored.
However, if most singular extension search conditions are true, except
"value < singularBeta", no non-singular extensions (e.g., castling) can
be performed!
Three tests were submitted, for three of Stockfish's four non-singular
extensions. I excluded the shuffle extension, because historically there
have been concerns about the fragility of its conditions, and I did not
want to risk causing any serious search problems.
- Modifying the passed pawn extension appeared roughly neutral at STC. At
best, it appeared to be an improvement of less than 1 Elo.
- Modifying check extension performed very poorly at STC
- Modifying castling extension (this patch) produced a long "yellow" run
at STC (insufficient to pass, but positive score) and a strong LTC.
In simple terms, prior to this patch castling extension was occasionally
not applied during search--on castling moves. The effect of this patch is
to perform castling extension on more castling moves. It does so without
adding any code complexity, simply by replacing an "else if" with "if" and
reordering some existing code.
STC:
LLR: -2.96 (-2.94,2.94) [0.00,4.00]
Total: 108114 W: 23877 L: 23615 D: 60622
http://tests.stockfishchess.org/tests/view/5d8d86bd0ebc590f3beb0c88
LTC:
LLR: 2.96 (-2.94,2.94) [0.00,4.00]
Total: 20862 W: 3517 L: 3298 D: 14047
http://tests.stockfishchess.org/tests/view/5d8d99cd0ebc590f3beb1899
Bench: 3728191
--------
Where do we go from here?
- It seems strange to me that check extension performed so poorly -- clearly
some of the singular extension conditions are also very important for check
extension. I am not an expert in search, and I do not have any intuition
about which of the eight conditions is/are the culprit. I will try a
succession of eight STC tests to identify the relevant conditions, then try
to replicate this PR for check extension.
- Recent tests interacting with the castle extension may deserve retesting.
I will shortly resubmit a few of my recent castling extension tweaks, rebased
on this PR/commit.
My deepest thanks to @noobpwnftw for the extraordinary CPU donation, and to
all our other fishtest volunteers, who made it possible for a speculative LTC
to pass in 70 minutes!
Closes https://github.com/official-stockfish/Stockfish/pull/2331
Remove the RookOnPawn logic (for rook on rank 5 and above aligning with pawns
on same row or file) which was overlapping with a few other parameters.
Inspired by @31m059 interesting result hinting that a direct attack on pawns
instead of PseudoAttacks might work.
http://tests.stockfishchess.org/tests/view/5d89a7c70ebc595091801b8d
After a few attempts by me and @31m059, and some long STC greens but red LTC,
as a proof of concept I first tried a local SPSA at VSTC trying to tune related
rook psqt rows, and mainly some rook related stuff in evaluate.cpp.
Result was STC green, but still red LTC,
Finally a 100M fishtest SPSA at LTC proved successful both at STC and LTC.
All this was possible with the awesome fishtest contributors.
At some point, I had 850 workers on the last test !
Run as a simplification
STC
http://tests.stockfishchess.org/tests/view/5d8d68f40ebc590f3beaf171
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 7399 W: 1693 L: 1543 D: 4163
LTC
http://tests.stockfishchess.org/tests/view/5d8d70270ebc590f3beaf63c
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 41617 W: 6981 L: 6894 D: 27742
Closes https://github.com/official-stockfish/Stockfish/pull/2329
bench: 4037914
Revert the previous patch now that the binary for the super-final
of TCEC season 16 has been sent.
Maybe the feature of showing the name of compiler will be added to the
master branch in the future. But we may use a cleaner way to code it, see
some ideas using the Makefile approach at the end of pull request #2327 :
https://github.com/official-stockfish/Stockfish/pull/2327
Bench: 3618154
This patch shows a description of the compiler used to compile Stockfish,
when starting from the console.
Usage:
```
./stockfish
compiler
```
Example of output:
```
Stockfish 240919 64 POPCNT by T. Romstad, M. Costalba, J. Kiiski, G. Linscott
Compiled by clang++ 9.0.0 on Apple
__VERSION__ macro expands to: 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.38)
```
No functional change
This patch replaces the obscure expressions mapping files ABCDEFGH to ABCDDCBA
by explicite calls to an auxiliary function:
old: f = min(f, ~f)
new: f = map_to_queenside(f)
We used the Golbolt web site (https://godbolt.org) to check that the current
code for the auxiliary function is optimal.
STC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 30292 W: 6756 L: 6651 D: 16885
http://tests.stockfishchess.org/tests/view/5d8676720ebc5971531d6aa1
Achieved with a bit of help from Sopel97, snicolet and vondele, thanks everyone!
Closes https://github.com/official-stockfish/Stockfish/pull/2325
No functional change
This change to the Rook psqt encourages rook lifts to the third rank
on the two center files.
STC 10+0.1 th 1 :
LLR: 2.96 (-2.94,2.94) [0.00,4.00]
Total: 40654 W: 9028 L: 8704 D: 22922
http://tests.stockfishchess.org/tests/view/5d885da60ebc5906dd3e9fcd
LTC 60+0.6 th 1 :
LLR: 2.96 (-2.94,2.94) [0.00,4.00]
Total: 56963 W: 9530 L: 9196 D: 38237
http://tests.stockfishchess.org/tests/view/5d88618c0ebc5906dd3ea45f
Thanks to @snicolet for mentioning that Komodo does this a lot and
Stockfish doesn't, which gave me the idea for this patch, and to
@noobpwnftw for providing cores to fishtest which allowed very quick
testing.
Future work: perhaps this can be refined somehow to encourage this
on other files, my attempts have failed.
Closes https://github.com/official-stockfish/Stockfish/pull/2322
Bench: 3950249
