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.
Read the FAQ or leave a comment.

!! latest version !!


Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: mstembera
Date: Mon Oct 25 12:26:44 2021 +0200
Timestamp: 1635157604

Fix sometimes incorrect key for prefetches

STC
https://tests.stockfishchess.org/tests/view/61737b4f6ce927be32558401
LLR: 2.95 (-2.94,2.94) <-2.50,0.50>
Total: 138712 W: 34914 L: 34942 D: 68856 Elo -0.07
Ptnml(0-2): 421, 14817, 38894, 14817, 407

Very minor tweak since Position::key() depends on the 50 move rule counter.
Comments: https://github.com/mstembera/Stockfish/commit/cddde31eed505cdf0c4fc8ff96b89f6e39c797e1

closes https://github.com/official-stockfish/Stockfish/pull/3759

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Joost VandeVondele
Date: Sun Oct 24 22:17:55 2021 +0200
Timestamp: 1635106675

Adjust ButterflyHistory decay parameter

passed STC:
LLR: 2.98 (-2.94,2.94) <-0.50,2.50>
Total: 26680 W: 6807 L: 6593 D: 13280 Elo +2.79
Ptnml(0-2): 73, 3007, 6989, 3175, 96
https://tests.stockfishchess.org/tests/view/6174094e6ce927be32558441

passed LTC:
LLR: 2.98 (-2.94,2.94) <0.50,3.50>
Total: 21104 W: 5403 L: 5185 D: 10516 Elo +3.59
Ptnml(0-2): 8, 2160, 6001, 2372, 11
https://tests.stockfishchess.org/tests/view/61744927351812fe5f969864

closes https://github.com/official-stockfish/Stockfish/pull/3761

Bench: 6334068
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Stefan Geschwentner
Date: Sun Oct 24 22:13:47 2021 +0200
Timestamp: 1635106427

Double extend search even more via LMR

Allow now for the first five moves a two plies deeper LMR search.

STC:
LLR: 2.96 (-2.94,2.94) <-2.50,0.50>
Total: 99608 W: 25143 L: 25115 D: 49350 Elo +0.10
Ptnml(0-2): 291, 11444, 26328, 11428, 313
https://tests.stockfishchess.org/tests/view/61718c9438cb9784038af8d7

LTC:
LLR: 2.95 (-2.94,2.94) <-2.50,0.50>
Total: 52064 W: 13234 L: 13145 D: 25685 Elo +0.59
Ptnml(0-2): 35, 5431, 15014, 5514, 38
https://tests.stockfishchess.org/tests/view/6171e13e38cb9784038af928

closes https://github.com/official-stockfish/Stockfish/pull/3760

Bench: 7222293
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: bmc4
Date: Sun Oct 24 22:08:28 2021 +0200
Timestamp: 1635106108

Simplify LMR multiThread condition

STC (8 threads):
LLR: 2.95 (-2.94,2.94) <-2.50,0.50>
Total: 110584 W: 27818 L: 27807 D: 54959 Elo +0.03
Ptnml(0-2): 156, 12089, 30791, 12100, 156
https://tests.stockfishchess.org/tests/view/6172ef436ce927be325583a9

LTC (8 threads):
LLR: 2.94 (-2.94,2.94) <-2.50,0.50>
Total: 23632 W: 6025 L: 5903 D: 11704 Elo +1.79
Ptnml(0-2): 5, 2292, 7100, 2414, 5
https://tests.stockfishchess.org/tests/view/6173cf096ce927be32558412

closes https://github.com/official-stockfish/Stockfish/pull/3757

No functional change (in the single-threaded case)
Bench: 6689428
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: FauziAkram
Date: Sat Oct 23 12:27:32 2021 +0200
Timestamp: 1634984852

Tuning of a Null Move Parameter

STC:
LLR: 2.99 (-2.94,2.94) <-0.50,2.50>
Total: 78744 W: 19956 L: 19664 D: 39124 Elo +1.29
Ptnml(0-2): 259, 9005, 20573, 9255, 280
https://tests.stockfishchess.org/tests/view/6172017a38cb9784038af947

LTC:
LLR: 2.95 (-2.94,2.94) <0.50,3.50>
Total: 68528 W: 17309 L: 16964 D: 34255 Elo +1.75
Ptnml(0-2): 41, 7194, 19455, 7527, 47
https://tests.stockfishchess.org/tests/view/6172994d38cb9784038af983

closes https://github.com/official-stockfish/Stockfish/pull/3756

bench: 6689428
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: bmc4
Date: Sat Oct 23 12:23:29 2021 +0200
Timestamp: 1634984609

Increase TTdepth acceptance some Threads

Increase TTdepth acceptance only on half of the Threads

STC:
LLR: 2.96 (-2.94,2.94) <-0.50,2.50>
Total: 19272 W: 4956 L: 4766 D: 9550 Elo +3.43
Ptnml(0-2): 25, 1989, 5423, 2169, 30
https://tests.stockfishchess.org/tests/view/6172be6238cb9784038af9a7

LTC:
LLR: 2.93 (-2.94,2.94) <0.50,3.50>
Total: 23688 W: 6111 L: 5897 D: 11680 Elo +3.14
Ptnml(0-2): 2, 2275, 7081, 2479, 7
https://tests.stockfishchess.org/tests/view/6172e32938cb9784038af9c7

closes https://github.com/official-stockfish/Stockfish/pull/3754

No functional change in the single-threaded case
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Stefano Cardanobile
Date: Sat Oct 23 12:22:02 2021 +0200
Timestamp: 1634984522

Rewrite NNUE evaluation adjustments

Make the eval code in the evaluate_nnue.cpp more similar to the rest of the codebase:

* remove multiple variable assignment
* make if conditions explicit and indent on multiple lines

passed STC
LLR: 2.93 (-2.94,2.94) <-2.50,0.50>
Total: 59032 W: 14834 L: 14751 D: 29447 Elo +0.49
Ptnml(0-2): 176, 6310, 16459, 6397, 174
https://tests.stockfishchess.org/tests/view/616f250540f619782fd4f76d

closes https://github.com/official-stockfish/Stockfish/pull/3753

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: mstembera
Date: Sat Oct 23 12:21:17 2021 +0200
Timestamp: 1634984477

Simplify away ValueListInserter

plus minor cleanups

STC: https://tests.stockfishchess.org/tests/view/616f059b40f619782fd4f73f
LLR: 2.94 (-2.94,2.94) <-2.50,0.50>
Total: 84992 W: 21244 L: 21197 D: 42551 Elo +0.19
Ptnml(0-2): 279, 9005, 23868, 9078, 266

closes https://github.com/official-stockfish/Stockfish/pull/3749

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Stefan Geschwentner
Date: Thu Oct 21 12:42:30 2021 +0200
Timestamp: 1634812950

Double extend more often via LMR

Allow for first three moves always a two plies deeper LMR search.

STC:
LLR: 2.96 (-2.94,2.94) <-2.50,0.50>
Total: 206096 W: 51966 L: 52093 D: 102037 Elo -0.21
Ptnml(0-2): 664, 23817, 54293, 23530, 744
https://tests.stockfishchess.org/tests/view/616f197d40f619782fd4f75a

LTC:
LLR: 2.93 (-2.94,2.94) <-2.50,0.50>
Total: 62384 W: 15567 L: 15492 D: 31325 Elo +0.42
Ptnml(0-2): 40, 6633, 17777, 6696, 46
https://tests.stockfishchess.org/tests/view/616ffa1b4f0b65a0e231e682

closes https://github.com/official-stockfish/Stockfish/pull/3752

Bench: 6154836
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: bmc4
Date: Thu Oct 21 08:43:43 2021 +0200
Timestamp: 1634798623

Simplify null move search condition

Remove `ss->ttPv` condition on null move search condition

STC:
LLR: 2.94 (-2.94,2.94) <-2.50,0.50>
Total: 80832 W: 20276 L: 20221 D: 40335 Elo +0.24
Ptnml(0-2): 267, 9335, 21168, 9368, 278
https://tests.stockfishchess.org/tests/view/616ed4a0942d40685e3237c6

LTC:
LLR: 2.95 (-2.94,2.94) <-2.50,0.50>
Total: 54184 W: 13464 L: 13377 D: 27343 Elo +0.56
Ptnml(0-2): 37, 5758, 15435, 5805, 57
https://tests.stockfishchess.org/tests/view/616ef71f40f619782fd4f72d

closes https://github.com/official-stockfish/Stockfish/pull/3750

bench: 6201607
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: bmc4
Date: Tue Oct 19 22:14:39 2021 +0200
Timestamp: 1634674479

Adjust TTdepth acceptance on early cutoff

STC:
LLR: 2.94 (-2.94,2.94) <-0.50,2.50>
Total: 63784 W: 16185 L: 15917 D: 31682 Elo +1.46
Ptnml(0-2): 231, 7309, 16531, 7603, 218
https://tests.stockfishchess.org/tests/view/616ed03a942d40685e3237c0

LTC:
LLR: 2.93 (-2.94,2.94) <0.50,3.50>
Total: 12728 W: 3268 L: 3072 D: 6388 Elo +5.35
Ptnml(0-2): 8, 1298, 3563, 1480, 15
https://tests.stockfishchess.org/tests/view/616ef156942d40685e32380a

closes https://github.com/official-stockfish/Stockfish/pull/3748

bench: 7050445
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: bmc4
Date: Tue Oct 19 22:09:47 2021 +0200
Timestamp: 1634674187

Simplify evaluate condition on search

Remove condition for MOVE_NULL on search.

STC:
LLR: 2.94 (-2.94,2.94) <-2.50,0.50>
Total: 47544 W: 11968 L: 11864 D: 23712 Elo +0.76
Ptnml(0-2): 150, 5535, 12318, 5599, 170
https://tests.stockfishchess.org/tests/view/616e37143799eb91f1f071ee

LTC:
LLR: 2.93 (-2.94,2.94) <-2.50,0.50>
Total: 67472 W: 16938 L: 16870 D: 33664 Elo +0.35
Ptnml(0-2): 49, 7119, 19331, 7189, 48
https://tests.stockfishchess.org/tests/view/616e3fab3799eb91f1f071f1

closes https://github.com/official-stockfish/Stockfish/pull/3746

bench: 5255771
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: bmc4
Date: Mon Oct 18 21:00:08 2021 +0200
Timestamp: 1634583608

Simplify probCutCount away

Simplify away the limitation in number of moves in probCut.

STC:
LLR: 2.96 (-2.94,2.94) <-2.50,0.50>
Total: 286768 W: 71888 L: 72133 D: 142747 Elo -0.30
Ptnml(0-2): 983, 33084, 75471, 32887, 959
https://tests.stockfishchess.org/tests/view/616c9b9b90e1312a3cd0ef0a

LTC:
LLR: 2.95 (-2.94,2.94) <-2.50,0.50>
Total: 69312 W: 17243 L: 17176 D: 34893 Elo +0.34
Ptnml(0-2): 42, 7452, 19614, 7493, 55
https://tests.stockfishchess.org/tests/view/616cebbf4f95b438f7a85f93

closes https://github.com/official-stockfish/Stockfish/pull/3745

bench: 5005810
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Stefano Cardanobile
Date: Mon Oct 18 20:45:47 2021 +0200
Timestamp: 1634582747

Reformat Eval::evaluate()

Non functional simplification: the goal of this patch is to make
the style in the evaluate() function similar to the rest of the code.

passed STC:
LLR: 2.94 (-2.94,2.94) <-2.50,0.50>
Total: 95608 W: 24058 L: 24026 D: 47524 Elo +0.12
Ptnml(0-2): 292, 10379, 26396, 10479, 258
https://tests.stockfishchess.org/tests/view/616c64fd99b580bf37797e4f

closes https://github.com/official-stockfish/Stockfish/pull/3744

Non-functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Stéphane Nicolet
Date: Sun Oct 17 17:54:39 2021 +0200
Timestamp: 1634486079

Remove noLMRExtension flag

This simplification patch removes the noLMRExtension flag. It was introduced in June
(see following link for that commit), but does not seem to be necessary anymore.
Link: https://github.com/official-stockfish/Stockfish/commit/e1f181ee643dcaa92c606b74b3abd23dede136cd

STC:
LLR: 2.94 (-2.94,2.94) <-2.50,0.50>
Total: 21200 W: 5369 L: 5228 D: 10603 Elo +2.31
Ptnml(0-2): 67, 2355, 5616, 2494, 68
https://tests.stockfishchess.org/tests/view/616c03d299b580bf37797dcb

LTC:
LLR: 2.94 (-2.94,2.94) <-2.50,0.50>
Total: 37536 W: 9387 L: 9278 D: 18871 Elo +1.01
Ptnml(0-2): 23, 3988, 10643, 4085, 29
https://tests.stockfishchess.org/tests/view/616c10f499b580bf37797ddd

closes https://github.com/official-stockfish/Stockfish/pull/3743

Bench: 4792969
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Stéphane Nicolet
Date: Sun Oct 17 12:29:11 2021 +0200
Timestamp: 1634466551

Allow some LMR double extensions

Allow some LMR double extensions for the second and third sons of each node.

STC:
LLR: 2.94 (-2.94,2.94) <-0.50,2.50>
Total: 170320 W: 42608 L: 42187 D: 85525 Elo +0.86
Ptnml(0-2): 516, 19635, 44422, 20086, 501
https://tests.stockfishchess.org/tests/view/616a9e3899b580bf37797cf4

LTC:
LLR: 2.93 (-2.94,2.94) <0.50,3.50>
Total: 74400 W: 18783 L: 18423 D: 37194 Elo +1.68
Ptnml(0-2): 46, 7812, 21129, 8162, 51
https://tests.stockfishchess.org/tests/view/616b378499b580bf37797d61

closes https://github.com/official-stockfish/Stockfish/pull/3742

Bench: 4877152
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Stefano Cardanobile
Date: Fri Oct 15 14:57:01 2021 +0200
Timestamp: 1634302621

Smooth improving

Smooth dependency on improvement margin in null move search.

STC
LLR: 2.93 (-2.94,2.94) <-0.50,2.50>
Total: 17384 W: 4468 L: 4272 D: 8644 Elo +3.92
Ptnml(0-2): 42, 1919, 4592, 2079, 60
https://tests.stockfishchess.org/tests/view/61689b8a1e5f6627cc1c0fdc

LTC
LLR: 2.94 (-2.94,2.94) <0.50,3.50>
Total: 45648 W: 11525 L: 11243 D: 22880 Elo +2.15
Ptnml(0-2): 26, 4731, 13036, 4997, 34
https://tests.stockfishchess.org/tests/view/6168a12c1e5f6627cc1c0fe3

It would be interesting to test if the other pruning/reduction heuristics
in master which are using the improving variable (ie the sign of improvement)
could benefit from a smooth function of the improvement value (or maybe a
Relu of the improvement value).

closes https://github.com/official-stockfish/Stockfish/pull/3740

Bench: 4916775
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Joost VandeVondele
Date: Thu Oct 14 09:58:03 2021 +0200
Timestamp: 1634198283

Compute ttCapture earlier

Compute ttCapture earlier, and reuse.

passed STC:
LLR: 2.93 (-2.94,2.94) <-2.50,0.50>
Total: 74128 W: 18640 L: 18578 D: 36910 Elo +0.29
Ptnml(0-2): 224, 7970, 20649, 7962, 259
https://tests.stockfishchess.org/tests/view/615dd9fa1a32f4036ac7fc4d

closes https://github.com/official-stockfish/Stockfish/pull/3734

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: bmc4
Date: Thu Oct 14 09:47:20 2021 +0200
Timestamp: 1634197640

Simplify ttHitAverage away

Simplify ttHitAverage away, which was introduced in the following commit:
[here](https://github.com/BM123499/Stockfish/commit/fe124896b241b4791454fd151da10101ad48f6d7)

A few tweaks with Elo gaining bounds have been tried to keep the code,
but they all failed:
https://tests.stockfishchess.org/tests/view/61656f7683dd501a05b0b292
https://tests.stockfishchess.org/tests/view/6165c0ca83dd501a05b0b2ca
https://tests.stockfishchess.org/tests/view/6165bf9683dd501a05b0b2c8
https://tests.stockfishchess.org/tests/view/6165719483dd501a05b0b29b
https://tests.stockfishchess.org/tests/view/6166c7fd83dd501a05b0b353
https://tests.stockfishchess.org/tests/view/6166c63b83dd501a05b0b350

STC:
LLR: 2.94 (-2.94,2.94) <-2.50,0.50>
Total: 58504 W: 14781 L: 14694 D: 29029 Elo +0.52
Ptnml(0-2): 175, 6718, 15426, 6711, 222
https://tests.stockfishchess.org/tests/view/6165112c83dd501a05b0b257

LTC:
LLR: 2.96 (-2.94,2.94) <-2.50,0.50>
Total: 33480 W: 8448 L: 8332 D: 16700 Elo +1.20
Ptnml(0-2): 21, 3569, 9447, 3679, 24
https://tests.stockfishchess.org/tests/view/61656fcf83dd501a05b0b294

change https://github.com/official-stockfish/Stockfish/pull/3739

bench: 4540339
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Joseph Ellis
Date: Wed Oct 13 23:34:23 2021 +0200
Timestamp: 1634160863

Simplify multi-cut condition

Now that the multi-cut condition is safer, we can avoid the cost of the sub-search.

STC:
https://tests.stockfishchess.org/tests/view/6165fd9283dd501a05b0b2fe
LLR: 2.93 (-2.94,2.94) <-2.50,0.50>
Total: 18648 W: 4745 L: 4600 D: 9303 Elo +2.70
Ptnml(0-2): 47, 2111, 4887, 2208, 71

LTC:
https://tests.stockfishchess.org/tests/view/616629ea83dd501a05b0b320
LLR: 2.96 (-2.94,2.94) <-2.50,0.50>
Total: 41704 W: 10407 L: 10302 D: 20995 Elo +0.87
Ptnml(0-2): 35, 4425, 11823, 4538, 31

closes https://github.com/official-stockfish/Stockfish/pull/3738

Bench: 5905086
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Michael Chaly
Date: Sat Oct 9 09:59:33 2021 +0200
Timestamp: 1633766373

Reduce more if multiple moves exceed alpha

Idea of this patch is the following: in case we already have four moves that
exceeded alpha in the current node, the probability of finding fifth should
be reasonably low. Note that four is completely arbitrary - there could and
probably should be some tweaks, both in tweaking best move count threshold
for more reductions and tweaking how they work - for example making more
reductions with best move count linearly.

passed STC:
https://tests.stockfishchess.org/tests/view/615f614783dd501a05b0aee2
LLR: 2.94 (-2.94,2.94) <-0.50,2.50>
Total: 141816 W: 36056 L: 35686 D: 70074 Elo +0.91
Ptnml(0-2): 499, 15131, 39273, 15511, 494

passed LTC:
https://tests.stockfishchess.org/tests/view/615fdff683dd501a05b0af35
LLR: 2.94 (-2.94,2.94) <0.50,3.50>
Total: 68536 W: 17221 L: 16891 D: 34424 Elo +1.67
Ptnml(0-2): 38, 6573, 20725, 6885, 47

closes https://github.com/official-stockfish/Stockfish/pull/3736

Bench: 6131513
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: xoto10
Date: Thu Oct 7 09:41:57 2021 +0200
Timestamp: 1633592517

Small clean-up, Sept 2021

Closes https://github.com/official-stockfish/Stockfish/pull/3485

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Stéphane Nicolet
Date: Wed Oct 6 12:04:35 2021 +0200
Timestamp: 1633514675

Capping stat bonus at 2000

This patch updates the stat_bonus() function (used in the history tables to
help move ordering), keeping the same quadratic for small depths but changing
the values for depth >= 9:

The old bonus formula was increasing from zero at depth 1 to 4100 at depth 14,
then used the strange, small value of 73 for all depths >= 15.

The new bonus formula increases from 0 at depth 1 to 2000 at depth 8, then
keeps 2000 for all depths >= 8.

passed STC:
LLR: 2.94 (-2.94,2.94) <-0.50,2.50>
Total: 169624 W: 42875 L: 42454 D: 84295 Elo +0.86
Ptnml(0-2): 585, 19340, 44557, 19729, 601
https://tests.stockfishchess.org/tests/view/615bd69e9d256038a969b97c

passed LTC:
LLR: 3.07 (-2.94,2.94) <0.50,3.50>
Total: 37336 W: 9456 L: 9191 D: 18689 Elo +2.47
Ptnml(0-2): 20, 3810, 10747, 4067, 24
https://tests.stockfishchess.org/tests/view/615c75d99d256038a969b9b2

closes https://github.com/official-stockfish/Stockfish/pull/3731

Bench: 6261865
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Joost VandeVondele
Date: Wed Oct 6 11:57:34 2021 +0200
Timestamp: 1633514254

Improve the Chess960 correction for cornered bishops

As Chess960 patches can not be tested on fishtest, this was locally tuned
and tested:

Elo: 2.36 +- 1.07
LOS: 0.999992

closes https://github.com/official-stockfish/Stockfish/pull/3730

Bench: 5714575
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: J. Oster
Date: Wed Oct 6 11:53:33 2021 +0200
Timestamp: 1633514013

Time-management fix in MultiPV mode.

When playing games in MultiPV mode we must take care to only track the
best move changing for the first PV line. Otherwise, SF will spend most
of its time for the initial moves after the book exit.

This has been observed and reported on Discord, but can also be seen in
games played in Stefan Pohl's MultiPV experiment.

Tested with MultiPV=4.

STC:
https://tests.stockfishchess.org/tests/view/615c24b59d256038a969b990
LLR: 2.95 (-2.94,2.94) <-0.50,2.50>
Total: 1744 W: 694 L: 447 D: 603 Elo +49.54
Ptnml(0-2): 32, 125, 358, 278, 79

LTC:
https://tests.stockfishchess.org/tests/view/615c31769d256038a969b993
LLR: 2.94 (-2.94,2.94) <0.50,3.50>
Total: 2048 W: 723 L: 525 D: 800 Elo +33.70
Ptnml(0-2): 10, 158, 511, 314, 31

closes https://github.com/official-stockfish/Stockfish/pull/3729

Bench: 5714575
see source

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