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 11.2/mingw 10 on Ubuntu 22.04.

Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: FauziAkram
Date: Thu May 9 09:00:32 2024 +0200
Timestamp: 1715238032

Simplify depth formula based on score improvement

Simplify depth formula based on score improvement.
This idea was first tried by cj5716

Passed STC:
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 347104 W: 89683 L: 89804 D: 167617 Elo -0.12
Ptnml(0-2): 1357, 38824, 93307, 38711, 1353
https://tests.stockfishchess.org/tests/view/66378edf9819650825aa75d0

Passed LTC:
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 63000 W: 15851 L: 15694 D: 31455 Elo +0.87
Ptnml(0-2): 22, 5396, 20499, 5569, 14
https://tests.stockfishchess.org/tests/view/663c04e5c0b75d7f7b97d461

closes https://github.com/official-stockfish/Stockfish/pull/5225

Bench: 2691699

Co-Authored-By: cj5716 <125858804+>
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
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: Thu May 9 08:56:36 2024 +0200
Timestamp: 1715237796

Remove conthist 3 from moves loop pruning

Followup to previous gainer that made it twice less impactful there - this patch removes it entirely as a simplification.

Passed STC:
https://tests.stockfishchess.org/tests/view/6637aa7e9819650825aa93e0
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 26208 W: 6930 L: 6694 D: 12584 Elo +3.13
Ptnml(0-2): 113, 2997, 6652, 3225, 117

Passed LTC:
https://tests.stockfishchess.org/tests/view/66383cba493aaaf4b7ea90c2
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 67866 W: 17294 L: 17118 D: 33454 Elo +0.90
Ptnml(0-2): 46, 7627, 18415, 7795, 50

closes https://github.com/official-stockfish/Stockfish/pull/5221

Bench: 2691699
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
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: Thu May 9 08:52:06 2024 +0200
Timestamp: 1715237526

Simplify away conthist 3 from statscore

Following previous elo gainer that gained by making conthist 3 less important in pruning this patch simplifies away this history from calculation of statscore.

Passed STC:
https://tests.stockfishchess.org/tests/view/6637aa7e9819650825aa93e0
LLR: 3.00 (-2.94,2.94) <-1.75,0.25>
Total: 35392 W: 9352 L: 9120 D: 16920 Elo +2.28
Ptnml(0-2): 141, 4145, 8888, 4385, 137

Passed LTC:
https://tests.stockfishchess.org/tests/view/66383cd8493aaaf4b7ea90c5
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 33948 W: 8714 L: 8503 D: 16731 Elo +2.16
Ptnml(0-2): 39, 3701, 9270, 3938, 26

closes https://github.com/official-stockfish/Stockfish/pull/5220

Bench: 2508571
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: FauziAkram
Date: Thu May 9 08:48:29 2024 +0200
Timestamp: 1715237309

simplify moveCountPruning

no (significant) speedup upon renewed testing

Passed stc:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 88992 W: 22779 L: 22633 D: 43580 Elo +0.57
Ptnml(0-2): 137, 8706, 26681, 8818, 154
https://tests.stockfishchess.org/tests/view/6636c4844b68b70d85800dae

closes https://github.com/official-stockfish/Stockfish/pull/5213

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
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: MinetaS
Date: Thu May 9 08:42:56 2024 +0200
Timestamp: 1715236976

Fix nodestime

1. The current time management system utilizes limits.inc and
limits.time, which can represent either milliseconds or node count,
depending on whether the nodestime option is active. There have been
several modifications which brought Elo gain for typical uses (i.e.
real-time matches), however some of these changes overlooked such
distinction. This patch adjusts constants and multiplication/division to
more accurately simulate real TC conditions when nodestime is used.

2. The advance_nodes_time function has a bug that can extend the time
limit when availableNodes reaches exact zero. This patch fixes the bug
by initializing the variable to -1 and make sure it does not go below
zero.

3. elapsed_time function is newly introduced to print PV in the UCI
output based on real time. This makes PV output more consistent with the
behavior of trivial use cases.

closes https://github.com/official-stockfish/Stockfish/pull/5186

No functional changes
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: rn5f107s2
Date: Thu May 9 08:38:04 2024 +0200
Timestamp: 1715236684

IIR on cutnodes if there is a ttMove but the ttBound is upper

If there is an upper bound stored in the transposition table, but we still have a ttMove, the upperbound indicates that the last time the ttMove was tried, it failed low. This fail low indicates that the ttMove may not be good, so this patch introduces a depth reduction of one for cutnodes with such ttMoves.

Passed STC:
https://tests.stockfishchess.org/tests/view/663be4d1ca93dad645f7f45f
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 139424 W: 35900 L: 35433 D: 68091 Elo +1.16
Ptnml(0-2): 425, 16357, 35743, 16700, 487

Passed LTC:
https://tests.stockfishchess.org/tests/view/663bec95ca93dad645f7f5c8
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 129690 W: 32902 L: 32390 D: 64398 Elo +1.37
Ptnml(0-2): 63, 14304, 35610, 14794, 74

closes https://github.com/official-stockfish/Stockfish/pull/5227

bench 2257437
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
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: Thu May 9 08:33:07 2024 +0200
Timestamp: 1715236387

Refactor quiet moves pruning in qsearch

Make it formula more in line with what we use in search - current formula is more or less the one we used years ago for search but since then it was remade, this patch remakes qsearch formula to almost exactly the same as we use in search - with sum of conthist 0, 1 and pawn structure history.

Passed STC:
https://tests.stockfishchess.org/tests/view/6639c8421343f0cb16716206
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 84992 W: 22414 L: 22019 D: 40559 Elo +1.61
Ptnml(0-2): 358, 9992, 21440, 10309, 397

Passed LTC:
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 119136 W: 30407 L: 29916 D: 58813 Elo +1.43
Ptnml(0-2): 46, 13192, 32622, 13641, 67

closes https://github.com/official-stockfish/Stockfish/pull/5224

Bench: 2138659
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: FauziAkram
Date: Thu May 9 08:29:33 2024 +0200
Timestamp: 1715236173

Depth dependent statscore based reductions

Test a modification of Fawzi's PR #5223, against that PR.

parameters locally tuned with nevergrad4sf.

passed STC:
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 1047424 W: 271478 L: 269649 D: 506297 Elo +0.61
Ptnml(0-2): 3851, 124543, 265290, 125982, 4046
https://tests.stockfishchess.org/tests/view/663b0889ca93dad645f7c58c

passed LTC:
LLR: 2.96 (-2.94,2.94) <0.50,2.50>
Total: 796236 W: 201712 L: 199825 D: 394699 Elo +0.82
Ptnml(0-2): 361, 88381, 218778, 90206, 392
https://tests.stockfishchess.org/tests/view/663be6adca93dad645f7f509

https://github.com/official-stockfish/Stockfish/pull/5228

Bench: 3346224
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: FauziAkram
Date: Thu May 9 08:26:35 2024 +0200
Timestamp: 1715235995

Tweak reduction formula based on depth

The idea came to me by checking for trends from the megafauzi tunes, since the values of the divisor for this specific formula were as follows:
stc: 15990
mtc: 16117
ltc: 14805
vltc: 12719
new vltc passed by Muzhen: 12076

This shows a clear trend related to time control, the higher it is, the lower the optimum value for the divisor seems to be.
So I tried a simple formula, using educated guesses based on some calculations, tests show it works pretty fine, and it can still be further tuned at VLTC in the future to scale even better.

Passed STC:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 431360 W: 110791 L: 109898 D: 210671 Elo +0.72
Ptnml(0-2): 1182, 50846, 110698, 51805, 1149
https://tests.stockfishchess.org/tests/view/663770409819650825aa269f

Passed LTC:
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 114114 W: 29109 L: 28625 D: 56380 Elo +1.47
Ptnml(0-2): 105, 12628, 31101, 13124, 99
https://tests.stockfishchess.org/tests/view/66378c099819650825aa73f6

https://github.com/official-stockfish/Stockfish/pull/5223

bench: 2273551
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Muzhen Gaming
Date: Sun May 5 15:11:53 2024 +0200
Timestamp: 1714914713

VVLTC search tune

This patch is the result of two tuning stages:
1. ~32k games at 60+0.6 th8:
https://tests.stockfishchess.org/tests/view/662d9dea6115ff6764c7f817
2. ~193k games at 80+0.8 th6, based on PR #5211:
https://tests.stockfishchess.org/tests/view/663587e273559a8aa857ca00.
Based on extensive VVLTC tuning and testing both before and after
#5211, it is observed that introduction of new extensions positively
affected the search tune results.

Passed VVLTC 70+0.7 th7 1st sprt: https://tests.stockfishchess.org/tests/view/6636c6f04b68b70d85801409
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 18566 W: 4864 L: 4620 D: 9082 Elo +4.57
Ptnml(0-2): 0, 1608, 5827, 1844, 4

Passed VVLTC 70+0.7 th7 2nd sprt: https://tests.stockfishchess.org/tests/view/6636d4b84b68b70d85802ab7
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 43142 W: 11141 L: 10838 D: 21163 Elo +2.44
Ptnml(0-2): 4, 3915, 13427, 4224, 1

Passed VVLTC 70+0.7 3rd sprt: https://tests.stockfishchess.org/tests/view/66376b4f9819650825aa230b
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 40322 W: 10374 L: 10076 D: 19872 Elo +2.57
Ptnml(0-2): 1, 3660, 12544, 3952, 4

The first two sprts were run against passed #5211. The third sprt was
run against latest master.

closes https://github.com/official-stockfish/Stockfish/pull/5216

Bench: 2180675
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: cj5716
Date: Sun May 5 15:11:37 2024 +0200
Timestamp: 1714914697

Simplify accumulator refreshes

Passed Non-Regression STC:
https://tests.stockfishchess.org/tests/view/6631f5d5d01fb9ac9bcdc7d0
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 57472 W: 14979 L: 14784 D: 27709 Elo +1.18
Ptnml(0-2): 185, 6486, 15192, 6695, 178

closes https://github.com/official-stockfish/Stockfish/pull/5207

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
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: Sun May 5 13:06:22 2024 +0200
Timestamp: 1714907182

Adjust history usage in moves loop pruning

After experiments with conthist 5 addition failed really bad divions by 2 passed as a gainer.

Passed STC:
https://tests.stockfishchess.org/tests/view/6636d7114b68b70d858035ce
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 35936 W: 9287 L: 8976 D: 17673 Elo +3.01
Ptnml(0-2): 81, 4129, 9234, 4446, 78

Passed LTC:
https://tests.stockfishchess.org/tests/view/6636ddb64b68b70d858040a8
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 82428 W: 21035 L: 20622 D: 40771 Elo +1.74
Ptnml(0-2): 29, 8985, 22775, 9394, 31

closes https://github.com/official-stockfish/Stockfish/pull/5217

Bench: 2309253
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: cj5716
Date: Sun May 5 13:04:37 2024 +0200
Timestamp: 1714907077

Some history fixes and tidy-up

This adds the functions `update_refutations` and `update_quiet_histories` to better distinguish the two. `update_quiet_stats` now just calls both of these functions.

The functional side of this patch is two-fold:
1. Stop refutations being updated when we carry out multicut
2. Update pawn history every time we update other quiet histories

Yellow STC:
LLR: -2.95 (-2.94,2.94) <0.00,2.00>
Total: 238976 W: 61506 L: 61415 D: 116055 Elo +0.13
Ptnml(0-2): 846, 28628, 60456, 28705, 853
https://tests.stockfishchess.org/tests/view/66321b5ed01fb9ac9bcdca83

However, it passed in <-1.75, 0.25> bounds:
$ python3 sprt.py --wins 61506 --losses 61415 --draws 116055 --elo0 -1.75 --elo1 0.25
ELO: 0.132 +- 0.998 [-0.865, 1.13]
LLR: 4.15 [-1.75, 0.25] (-2.94, 2.94)
H1 Accepted

Passed LTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 399126 W: 100730 L: 100896 D: 197500 Elo -0.14
Ptnml(0-2): 116, 44328, 110843, 44158, 118
https://tests.stockfishchess.org/tests/view/66357b0473559a8aa857ba6f

closes #5215

Bench 2370967
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: FauziAkram
Date: Sun May 5 13:02:42 2024 +0200
Timestamp: 1714906962

Simplify shuffling and optimism divisors to constants

Shuffling divisor and Optimism divisors passed STC & LTC separately:
shuf STC: https://tests.stockfishchess.org/tests/view/66356316b4e9bdbc7228b995
shuf LTC: https://tests.stockfishchess.org/tests/view/6635815a73559a8aa857c1dc
opt STC: https://tests.stockfishchess.org/tests/view/66356326b4e9bdbc7228b9a0
opt LTC: https://tests.stockfishchess.org/tests/view/663615c673559a8aa8589f8a

And then passed LTC together:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 178278 W: 45039 L: 44979 D: 88260 Elo +0.12
Ptnml(0-2): 43, 19776, 49460, 19798, 62
https://tests.stockfishchess.org/tests/view/66363f19cdb7cf5da64e22a3

closes https://github.com/official-stockfish/Stockfish/pull/5212

Bench: 2198243
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Viren6
Date: Sun May 5 12:53:58 2024 +0200
Timestamp: 1714906438

Introduce Quadruple Extensions

This patch introduces quadruple extensions, with the new condition of not ttPv. It also generalises all margins, so that extensions can still occur if conditions are only partially fulfilled, but with a stricter margin.

Failed STC:
LLR: -2.94 (-2.94,2.94) <0.00,2.00>
Total: 16096 W: 3984 L: 4228 D: 7884 Elo -5.27
Ptnml(0-2): 72, 2067, 4002, 1847, 60
https://tests.stockfishchess.org/tests/view/66316422d01fb9ac9bcdbdcd

Passed VVLTC 1:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 96660 W: 24550 L: 24210 D: 47900 Elo +1.22
Ptnml(0-2): 5, 8776, 30426, 9120, 3
https://tests.stockfishchess.org/tests/view/66361f2c74fa3f41ef2ee091

Passed VVLTC 2:
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 80546 W: 20495 L: 20120 D: 39931 Elo +1.62
Ptnml(0-2): 6, 7477, 24929, 7858, 3
https://tests.stockfishchess.org/tests/view/66350cf739ba8e443112b3fa

closes https://github.com/official-stockfish/Stockfish/pull/5211

bench 2233743
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
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: Sun May 5 12:42:30 2024 +0200
Timestamp: 1714905750

Add extra bonuses to some moves that forced a fail low

The previous patch on this idea was giving bonuses to this moves if best value of search is far below current static evaluation.
This patch does similar thing but adds extra bonus when best value of search is far below static evaluation before previous move.

Passed STC:
https://tests.stockfishchess.org/tests/view/66355fc819566d64b481d6a4
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 454144 W: 116575 L: 115656 D: 221913 Elo +0.70
Ptnml(0-2): 1060, 53410, 117215, 54325, 1062

Passed LTC:
https://tests.stockfishchess.org/tests/view/6635c61a73559a8aa858012d
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 136578 W: 34858 L: 34335 D: 67385 Elo +1.33

closes https://github.com/official-stockfish/Stockfish/pull/5209

Bench: 1614825
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: cj5716
Date: Sun May 5 12:36:20 2024 +0200
Timestamp: 1714905380

Remove PSQT-only mode

Passed STC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 94208 W: 24270 L: 24112 D: 45826 Elo +0.58
Ptnml(0-2): 286, 11186, 24009, 11330, 293
https://tests.stockfishchess.org/tests/view/6635ddd773559a8aa8582826

Passed LTC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 114960 W: 29107 L: 28982 D: 56871 Elo +0.38
Ptnml(0-2): 37, 12683, 31924, 12790, 46
https://tests.stockfishchess.org/tests/view/663604a973559a8aa85881ed

closes #5214

Bench 1653939
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Disservin
Date: Sun May 5 12:30:28 2024 +0200
Timestamp: 1714905028

Clear Workers after changing the network

ensures internal state (e.g. accumulator cache) is consistent with network

closes https://github.com/official-stockfish/Stockfish/pull/5204

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
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: mstembera
Date: Wed May 1 14:17:32 2024 +0200
Timestamp: 1714565852

Accumulator cache bugfix and cleanup

STC:
https://tests.stockfishchess.org/tests/view/663068913a05f1bf7a511dc2
LLR: 2.98 (-2.94,2.94) <-1.75,0.25>
Total: 70304 W: 18211 L: 18026 D: 34067 Elo +0.91
Ptnml(0-2): 232, 7966, 18582, 8129, 243

1) Fixes a bug introduced in
https://github.com/official-stockfish/Stockfish/pull/5194. Only one
psqtOnly flag was used for two perspectives which was causing
wrong entries to be cleared and marked.
2) The finny caches should be cleared like histories and not at the
start of every search.

closes https://github.com/official-stockfish/Stockfish/pull/5203

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
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: cj5716
Date: Wed May 1 14:10:57 2024 +0200
Timestamp: 1714565457

Optimise NNUE Accumulator updates

Passed STC:
https://tests.stockfishchess.org/tests/view/662e3c6a5e9274400985a741
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 86176 W: 22284 L: 21905 D: 41987 Elo +1.53
Ptnml(0-2): 254, 9572, 23051, 9963, 248

closes https://github.com/official-stockfish/Stockfish/pull/5202

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
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Ciekce
Date: Wed May 1 14:10:57 2024 +0200
Timestamp: 1714565457

Avoid unnecessary creation of accumulator cache

Saves a (currently) 800 KB allocation and deallocation when running
`eval`, not particularly significant and zero impact on play but not
necessary either.

closes https://github.com/official-stockfish/Stockfish/pull/5201

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
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Dubslow
Date: Wed May 1 14:10:50 2024 +0200
Timestamp: 1714565450

Use capture history to better judge which sacrifices to explore

This idea has been bouncing around a while. @Vizvezdenec tried it a
couple years ago in Stockfish without results, but its recent arrival in
Ethereal inspired him and thence me to try it afresh in Stockfish.

(Also factor out the now-common code with futpruning for captures.)

STC:
https://tests.stockfishchess.org/tests/view/662355bc3fe04ce4cefc18ac
LLR: 2.92 (-2.94,2.94) <0.00,2.00>
Total: 45760 W: 11970 L: 11640 D: 22150 Elo +2.51
Ptnml(0-2): 124, 5371, 11625, 5571, 189

LTC:
https://tests.stockfishchess.org/tests/view/662dda396115ff6764c817c9
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 243828 W: 62042 L: 61287 D: 120499 Elo +1.08
Ptnml(0-2): 211, 27202, 66329, 27965, 207

closes https://github.com/official-stockfish/Stockfish/pull/5200

Bench: 1480008
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
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 Apr 28 21:46:45 2024 +0200
Timestamp: 1714333605

More reduction at cut nodes which are not a former PV node

But the tt move and first killer are excluded.

This idea is based on following LMR condition tuning
https://tests.stockfishchess.org/tests/view/66228bed3fe04ce4cefc0c71 by
using only the two largest terms P[0] and P[1].

Passed STC:
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 173248 W: 45091 L: 44565 D: 83592 Elo +1.05
Ptnml(0-2): 693, 20534, 43673, 21002, 722
https://tests.stockfishchess.org/tests/view/6629603b3fe04ce4cefc7d37

Passed LTC:
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 722394 W: 183231 L: 181487 D: 357676 Elo +0.84
Ptnml(0-2): 462, 80650, 197252, 82348, 485
https://tests.stockfishchess.org/tests/view/662cbe45d46f72253dcff7bf

closes https://github.com/official-stockfish/Stockfish/pull/5199

Bench: 1619613
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
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 Apr 28 21:43:46 2024 +0200
Timestamp: 1714333426

Simplify non-pawn material divisor to a constant

Passed STC:
https://tests.stockfishchess.org/tests/view/662942603fe04ce4cefc7aba
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 272832 W: 70456 L: 70497 D: 131879 Elo -0.05
Ptnml(0-2): 1020, 32619, 69154, 32628, 995

Passed LTC:
https://tests.stockfishchess.org/tests/view/662dfe3b6115ff6764c829eb
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 100254 W: 25446 L: 25303 D: 49505 Elo +0.50
Ptnml(0-2): 121, 11292, 27166, 11419, 129

closes https://github.com/official-stockfish/Stockfish/pull/5198

Bench: 1544645
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: cj5716
Date: Sun Apr 28 21:36:34 2024 +0200
Timestamp: 1714332994

Penalise the TT move in multicut

Passed STC:
LLR: 2.99 (-2.94,2.94) <0.00,2.00>
Total: 185504 W: 48079 L: 47533 D: 89892 Elo +1.02
Ptnml(0-2): 716, 21866, 46988, 22520, 662
https://tests.stockfishchess.org/tests/view/662d9e1d6115ff6764c7f83d

Passed LTC:
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 75612 W: 19351 L: 18948 D: 37313 Elo +1.85
Ptnml(0-2): 46, 8363, 20592, 8752, 53
https://tests.stockfishchess.org/tests/view/662dc9dc6115ff6764c80fea

closes https://github.com/official-stockfish/Stockfish/pull/5195

Bench: 1415435
see source

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