Stockfish Development Versions are build automatically if there are changes on the master branch in the git repository (https://github.com/official-stockfish/Stockfish). Use it at your own risk.
They are compiled with gcc/mingw 7.3 on Ubuntu 18.04.
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!! latest version !!


Windows x64 for Haswell CPUs
Windows x64 for modern computers
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Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Guenther Demetz
Date: Tue Dec 10 08:07:34 2019 +0100
Timestamp: 1575961654

Refine improving-logic

Don't rely on the assumption that we are improving after surviving a
check. Instead, compare with the static eval of 2 moves before.

STC
https://tests.stockfishchess.org/tests/view/5dedfd7f3cff9a249bb9e44d
LLR: 2.95 (-2.94,2.94) [-1.50,4.50]
Total: 38859 W: 8621 L: 8397 D: 21841 Elo +2.00

LTC
https://tests.stockfishchess.org/tests/view/5dee1b5a3cff9a249bb9e465
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 51130 W: 8308 L: 7996 D: 34826 Elo +2.12

Bench: 5371271
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: lantonov
Date: Tue Dec 10 01:10:19 2019 +0100
Timestamp: 1575936619

Tuned razor and futility margins

Tuning was done with Bayesian optimisation with the following parameters:
Acquisition function: Expected Improvement
alpha: 0.05
xi: 1e-4
TC: 60+0.6
Number of iterations: 100
Initial points: 5
Batch size: 20 games

STC
http://tests.stockfishchess.org/tests/view/5dee291e3cff9a249bb9e470
LLR: 2.97 (-2.94,2.94) [-1.50,4.50]
Total: 19586 W: 4382 L: 4214 D: 10990 Elo +2.98

LTC
http://tests.stockfishchess.org/tests/view/5dee4e273cff9a249bb9e473
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 38840 W: 6315 L: 6036 D: 26489 Elo +2.50

Bench: 5033242
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: xoto10
Date: Tue Dec 10 01:04:07 2019 +0100
Timestamp: 1575936247

TrappedRook value and King positional tables

Small tweak to increase the TrappedRook penalty. Nice idea by Alain Savard!

STC
LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 36977 W: 8212 L: 7993 D: 20772 Elo +2.06
https://tests.stockfishchess.org/tests/view/5dee1c1e3cff9a249bb9e46d

LTC
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 36395 W: 6070 L: 5795 D: 24530 Elo +2.63
https://tests.stockfishchess.org/tests/view/5dee90153cff9a249bb9e479

Closes https://github.com/official-stockfish/Stockfish/pull/2447

Bench: 5176990

-------------------------

Comments by Alain Savard:

For the record, the idea was to run an experimental tuning with disabled
castling in the hope to get more hits on the TrappedRook and the king in
the c1- f1-f2-c2 area
http://tests.stockfishchess.org/tests/view/5dec57be51219d7befdc76e1

A first interpretation of that tuning was green STC (0, 4) and yellow LTC (0, 4):
http://tests.stockfishchess.org/tests/view/5ded04bc51219d7befdc773a
http://tests.stockfishchess.org/tests/view/5ded1e7a51219d7befdc7760

Thank you @xoto for trying this. Indeed, because the tuned Kc2 and Kf2 values
were quite different, it was a good idea to try something more neutral.
Windows x64 for Haswell CPUs
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Linux x64
Author: Vizvezdenec
Date: Mon Dec 9 00:38:16 2019 +0100
Timestamp: 1575848296

Exclude blockers for king from mobility area

This patch excludes blockers for king from mobility area. It was tried a couple
of times by now but now it passed. Performance is not enormously good but this
patch makes a lot of sence - blockers for king can't really move until king moves
(in most cases) so logic behind it is the same as behind excluding king square
from mobility area.

STC
http://tests.stockfishchess.org/tests/view/5dec388651219d7befdc76be
LLR: 2.95 (-2.94,2.94) [-1.50,4.50]
Total: 6155 W: 1428 L: 1300 D: 3427 Elo +7.23

LTC
http://tests.stockfishchess.org/tests/view/5dec4a3151219d7befdc76d3
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 120800 W: 19636 L: 19134 D: 82030 Elo +1.44

Bench: 5173081
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Vizvezdenec
Date: Mon Dec 9 00:32:37 2019 +0100
Timestamp: 1575847957

Do last capture extensions for every single node

This patch simplifies latest @MJZ1977 elo gainer. Seems like PvNode check in
condition of last capture extension is not needed. Note - even if this is a
simplification it actually causes this extension to be applied more often, thus
strengthening effect of @MJZ1977's patch.

passed STC
http://tests.stockfishchess.org/tests/view/5deb9a3eb7bdefd50db28d0e
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 80244 W: 17421 L: 17414 D: 45409 Elo +0.03

passed LTC
http://tests.stockfishchess.org/tests/view/5deba860b7bdefd50db28d11
LLR: 2.94 (-2.94,2.94) [-3.00,1.00]
Total: 21506 W: 3565 L: 3446 D: 14495 Elo +1.92

Bench: 5097036
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: protonspring
Date: Mon Dec 9 00:27:12 2019 +0100
Timestamp: 1575847632

Simplify pruning moves with negative SEE

This patch simplifies pruning moves with negative SEE values.

STC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 18847 W: 4211 L: 4084 D: 10552 Elo +2.34
http://tests.stockfishchess.org/tests/view/5de983f2caa7c610e4d1866e

LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 25556 W: 4200 L: 4087 D: 17269 Elo +1.54
http://tests.stockfishchess.org/tests/view/5de99e21caa7c610e4d18676

Bench 5390930
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: joergoster
Date: Mon Dec 9 00:16:55 2019 +0100
Timestamp: 1575847015

Fix output of PV lines with invalid scores #2439

As reported on the forum it is possible, on very rare occasions, that we are
trying to print a PV line with an invalid previousScore, although this line
has a valid actual score. This patch fixes output of PV lines with invalid
scores in a MultiPV search. This is a follow-up patch to 8b15961 and makes
the fix finally complete.

The reason is the i <= pvIdx condition which probably is a leftover from the
times there was a special root search function. This check is no longer needed
today and prevents PV lines past the current one (current pvIdx) to be flagged
as updated even though they do have a valid score.

https://github.com/official-stockfish/Stockfish/commit/8b15961349e18a9ba113973c53f53913d0cd0fad
https://groups.google.com/forum/?fromgroups=#!topic/fishcooking/PrnoDLvMvro

No functional change.
Windows x64 for Haswell CPUs
Windows x64 for modern computers
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Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: xoto10
Date: Mon Dec 9 00:10:47 2019 +0100
Timestamp: 1575846647

Tweak time management (failing eval)

Adjust fallingEval with score change in last 5 iterations. FallingEval adjusts
the time used on a move depending on whether the position score is better or
worse than on the previous move. This change adds a dependency on the score
change in the last 5 iterations of the current search.

Tests with original code:
STC :
LLR: 2.97 (-2.94,2.94) [-1.50,4.50]
Total: 18728 W: 4170 L: 4005 D: 10553 Elo +3.06
https://tests.stockfishchess.org/tests/view/5de68a5bb407ee7bfda68a94

LTC :
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 180217 W: 29214 L: 28551 D: 122452 Elo +1.28
https://tests.stockfishchess.org/tests/view/5de690a4b407ee7bfda68a9a

Revised code using a simple array instead of a deque and different values
gave a slightly quicker pass at LTC. The merged patch now uses this:

STC :
LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 18616 W: 4114 L: 3950 D: 10552 Elo +3.06
https://tests.stockfishchess.org/tests/view/5debb790b7bdefd50db28d14

LTC :
LLR: 2.96 (-2.94,2.94) [0.00,3.50]
Total: 134151 W: 21729 L: 21191 D: 91231 Elo +1.39
https://tests.stockfishchess.org/tests/view/5debc13fb7bdefd50db28d19

No functional change
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Joost VandeVondele
Date: Mon Dec 9 00:05:25 2019 +0100
Timestamp: 1575846325

Remove unneeded & incorrect check.

the removed line is not needed, since with the conditions on SE, eval
equals ttValue (except inCheck), which must be larger than beta if the second condition
is true.

The removed line is also incorrect as eval might be VALUE_NONE at this
location if inCheck. This removal addresses part of https://github.com/official-stockfish/Stockfish/pull/2406#issuecomment-552642608

No functional change.
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
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Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Stéphane Nicolet
Date: Mon Dec 9 00:00:34 2019 +0100
Timestamp: 1575846034

The sudo tag is deprecated in Travis CI

Reported by Christian Clauss. Thanks!

No functional change
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: FauziAkram
Date: Tue Dec 3 00:27:58 2019 +0100
Timestamp: 1575329278

UnblockedStorm tuned

STC
http://tests.stockfishchess.org/tests/view/5de155980294ec4750cba9bd
LLR: 2.96 (-2.94,2.94) [0.00,4.00]
Total: 60206 W: 13295 L: 12895 D: 34016 Elo +2.31

LTC
http://tests.stockfishchess.org/tests/view/5de22f6f0294ec4750cba9e7
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 182005 W: 29571 L: 28902 D: 123532 Elo +1.28

VLTC
http://tests.stockfishchess.org/tests/view/5de4adca5e868d334be516c1
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 42101 W: 6068 L: 5978 D: 30055 Elo +0.74

Bench: 5122362
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Alain SAVARD
Date: Sun Dec 1 19:12:39 2019 +0100
Timestamp: 1575223959

King proximity tweak for passed pawns

Decrease slightly the penalty for opponent king distance to passed pawn.
Instead of 5:2 ratio (or 20:8) we now have 19:8

STC
http://tests.stockfishchess.org/tests/view/5de281b2727dc1d26718a673
LLR: 2.95 (-2.94,2.94) [-1.50,4.50]
Total: 28638 W: 6297 L: 6104 D: 16237 Elo +2.34

LTC
http://tests.stockfishchess.org/tests/view/5de2a2ff727dc1d26718a67b
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 59586 W: 9766 L: 9429 D: 40391 Elo +1.97

Where to go from here:
Further tests will try a similar tweak on the friendly king proximity penalty,
because recent experiments indicate that this penalty is quite sensitive,
but I wanted to try first on the larger term.

Closes https://github.com/official-stockfish/Stockfish/pull/2435

bench: 5258928

---------------

Increasing the penalty ratio to 21:8 was neutral.
http://tests.stockfishchess.org/tests/view/5de2814d727dc1d26718a671

Decreasing the penalty ratio a bit more to 9:4 seems less promising
http://tests.stockfishchess.org/tests/view/5de2f4c2727dc1d26718a691
http://tests.stockfishchess.org/tests/view/5de32ecc727dc1d26718a6b0
Windows x64 for Haswell CPUs
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Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Joost VandeVondele
Date: Thu Nov 28 10:39:02 2019 +0100
Timestamp: 1574933942

Extend bench to static evaluations

this patch extends bench to print static evaluations.

./stockfish bench 16 1 1 filename eval

will now print the evaluations for all fens in the file.

This complements the various 'go' flavors for bench and might be useful for debugging and/or tuning.

No functional change.
Windows x64 for Haswell CPUs
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Windows x64
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Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Vizvezdenec
Date: Tue Nov 26 01:28:05 2019 +0100
Timestamp: 1574728085

Simplify king danger

This patch is a cleanup/simplification of king flank defenders patch,
removing king flanks attacks linear dependance in kingdanger. Result
of experiments with quadratic kingflank defenders scaling. Rebased on
the latest master.

passed STC
http://tests.stockfishchess.org/tests/view/5ddc2b99e0b4af579302bacf
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 19660 W: 4309 L: 4184 D: 11167 Elo +2.21

passed LTC
http://tests.stockfishchess.org/tests/view/5ddc3168e0b4af579302bade
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 24362 W: 3974 L: 3859 D: 16529 Elo +1.64

Closes https://github.com/official-stockfish/Stockfish/pull/2428

bench 5742013
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Moez Jellouli
Date: Tue Nov 26 00:01:49 2019 +0100
Timestamp: 1574722909

Extend last non-pawn captures

Extend last non-pawn captures at principal variation nodes because
they are in general decisive moves with clear endgame result.

STC
http://tests.stockfishchess.org/tests/view/5ddafc86e75c0005326d2140
LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 9892 W: 2238 L: 2099 D: 5555 Elo +4.88

LTC
http://tests.stockfishchess.org/tests/view/5ddb0401e75c0005326d2150
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 30369 W: 5013 L: 4756 D: 20600 Elo +2.94

Closes https://github.com/official-stockfish/Stockfish/pull/2425

Bench: 5059526
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: 31m059
Date: Sun Nov 24 00:34:43 2019 +0100
Timestamp: 1574552083

King danger: retire attacked-by-bishop defense

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 Elo +1.88
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 Elo -0.19
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!
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: SFisGOD
Date: Sun Nov 24 00:23:06 2019 +0100
Timestamp: 1574551386

Simplify endgame factor for opposite colored bishops

Stockfish is continually improving. Patches that gain elo in the past may
no longer be needed as stockfish improved elsewhere. This patch removes
passed pawns count dependence in opposite colored bishops scale factor.
We used the mean of passed count pawns (~1.4) to compensate, and changed
the base value from 16 to 22.

Passed STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 57879 W: 12657 L: 12607 D: 32615 Elo +0.30
http://tests.stockfishchess.org/tests/view/5dd1644f42928ff08153dc1e

Passed LTC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 121648 W: 19622 L: 19659 D: 82367 Elo -0.11
http://tests.stockfishchess.org/tests/view/5dd24572ccb823d41d4b47bb

Closes https://github.com/official-stockfish/Stockfish/pull/2419

Bench: 5067864
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Vizvezdenec
Date: Thu Nov 21 09:52:13 2019 +0100
Timestamp: 1574326333

Do lmr for more captures

Based on machinery introduced by vondele. Logic behind patch if relatively simple -
if we reduce less with high hit rate of transposition table somewhat logical is to
reduce more with low hit rate. For example enable all captures for LMR.

Threshold 0.375 is arbitrary and can be tweaked :)

STC
http://tests.stockfishchess.org/tests/view/5dd4d51df531e81cf278eaac
LLR: 2.97 (-2.94,2.94) [-1.50,4.50]
Total: 16495 W: 3591 L: 3434 D: 9470 Elo +3.31

LTC
http://tests.stockfishchess.org/tests/view/5dd52265f531e81cf278eace
LLR: 2.96 (-2.94,2.94) [0.00,3.50]
Total: 23598 W: 3956 L: 3716 D: 15926 Elo +3.53

Closes https://github.com/official-stockfish/Stockfish/pull/2420

Bench: 5067870
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Alain SAVARD
Date: Thu Nov 21 09:32:19 2019 +0100
Timestamp: 1574325139

Outpost Endgame values

Remove the recent rank based Outpost array by using a weighted average value
computed using a frequency analysis by rank from a large set of middle game
positions.

The higher eg values introduced by the new Outpost array (which were about
twice the previous masters) are thus preserved.

STC
http://tests.stockfishchess.org/tests/view/5dd05c870ebc5902579e1f7f
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 42466 W: 9232 L: 9151 D: 24083 Elo +0.66

LTC
http://tests.stockfishchess.org/tests/view/5dd146e342928ff08153dab1
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 66968 W: 10921 L: 10873 D: 45174 Elo +0.25

Closes https://github.com/official-stockfish/Stockfish/pull/2418

Bench: 5103360
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Vizvezdenec
Date: Tue Nov 19 23:18:14 2019 +0100
Timestamp: 1574201894

Simplify advanced pawn push pruning

This patch simplifies away all conditions related to advanced pawn pushes
in shallow depth pruning. Idea is based on fact that in master we have
advanced pawn pushes not being pruned what we are only in PV node and
when non-pawn material of opponent is > Bishop, so pretty rarely. With
this patch we will have all pruning heuristics working for this moves as
for every other move.

STC
LLR: 2.94 (-2.94,2.94) [-3.00,1.00]
Total: 159143 W: 34271 L: 34418 D: 90454 Elo -0.32
http://tests.stockfishchess.org/tests/view/5dcdb3110ebc5902563249d7

LTC
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 63900 W: 10375 L: 10322 D: 43203 Elo +0.29
http://tests.stockfishchess.org/tests/view/5dd05e820ebc5902579e1fb8

Closes https://github.com/official-stockfish/Stockfish/pull/2416

bench 4897149
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Joost VandeVondele
Date: Mon Nov 18 09:57:53 2019 +0100
Timestamp: 1574067473

Use exploration rate for reductions

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 Elo +2.46
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 Elo +2.84
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 Elo +3.38
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 Elo +2.58
http://tests.stockfishchess.org/tests/view/5dd0f58e6f544e798086f224

Closes https://github.com/official-stockfish/Stockfish/pull/2414

Bench: 4989584
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Vizvezdenec
Date: Sat Nov 16 17:29:53 2019 +0100
Timestamp: 1573921793

Introduce king flank defenders

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 Elo +2.47

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 Elo +2.93

Closes https://github.com/official-stockfish/Stockfish/pull/2415

Bench: 4496847
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Stefan Geschwentner
Date: Thu Nov 14 20:26:15 2019 +0100
Timestamp: 1573759575

Prune before extension

Switch execution order in search: do move pruning before extension detection.

STC:
LLR: 2.96 (-2.94,2.94) [-1.50,4.50]
Total: 5762 W: 1307 L: 1181 D: 3274 Elo +7.60
http://tests.stockfishchess.org/tests/view/5dcc56e90ebc59025bcbb833

LTC:
LLR: 2.96 (-2.94,2.94) [0.00,3.50]
Total: 72956 W: 11959 L: 11585 D: 49412 Elo +1.78
http://tests.stockfishchess.org/tests/view/5dcc62840ebc59025bcbb96f

Closes https://github.com/official-stockfish/Stockfish/pull/2413

Bench: 4532366
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: SFisGOD
Date: Wed Nov 13 11:01:00 2019 +0100
Timestamp: 1573639260

Rank-based outposts

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 Elo +2.40
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 Elo +1.98
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.
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers
Linux x64
Author: Miguel Lahoz
Date: Tue Nov 12 01:36:06 2019 +0100
Timestamp: 1573518966

Shallow depth pruning on NonPV advanced pawn push

Usually advanced pawn pushes are not considered in shallow depth pruning
because it is risky to do so with possible promotions near the horizon.
However, this heuristic is not also beneficial on NonPV nodes since we
can afford to take slightly more risk on less important nodes.

STC:
LLR: 2.95 (-2.94,2.94) [-1.50,4.50]
Total: 54530 W: 11955 L: 11686 D: 30889 Elo +1.71
http://tests.stockfishchess.org/tests/view/5dc7dda30ebc5902ea57efd0

LTC:
LLR: 2.95 (-2.94,2.94) [0.00,3.50]
Total: 77336 W: 12786 L: 12399 D: 52151 Elo +1.74
http://tests.stockfishchess.org/tests/view/5dc8050d0ebc5902ea57f491

Closes https://github.com/official-stockfish/Stockfish/pull/2408

Bench: 4422068

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