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 modern computers + AVX2
Windows x64 + SSSE3
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Carlos Esparza
Date: Thu Feb 13 19:44:53 2025 +0100
Timestamp: 1739472293

Remove two xors by setting the hash keys for unreachable squares to zero

performance before:
3.6714 +- 0.20% Gcycles
3.6620 +- 0.12% Gcycles
3.6704 +- 0.26% Gcycles
3.6602 +- 0.27% Gcycles
3.6799 +- 0.37% Gcycles

after:
3.6540 +- 0.30% Gcycles
3.6388 +- 0.25% Gcycles
3.6557 +- 0.17% Gcycles
3.6449 +- 0.15% Gcycles
3.6460 +- 0.26% Gcycles

(every line is a different `profile-build` and shows the number of
cycles needed for `./stockfish bench`, measured with `perf stat -r 10`)

closes https://github.com/official-stockfish/Stockfish/pull/5754

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: Shawn Xu
Date: Wed Feb 5 19:00:25 2025 +0100
Timestamp: 1738778425

Increase PCM bonus when cutOffCnt is low

Passed STC:
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 36832 W: 9763 L: 9438 D: 17631 Elo +3.07
Ptnml(0-2): 159, 4267, 9254, 4562, 174
https://tests.stockfishchess.org/tests/view/67a29dbafedef70e42ac329a

Passed LTC:
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 19728 W: 5124 L: 4839 D: 9765 Elo +5.02
Ptnml(0-2): 18, 2029, 5485, 2314, 18
https://tests.stockfishchess.org/tests/view/67a2a1abfedef70e42ac32b7

closes https://github.com/official-stockfish/Stockfish/pull/5865

Bench: 3197798
see source
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: Daniel Monroe
Date: Wed Feb 5 18:56:12 2025 +0100
Timestamp: 1738778172

Remove non-pawn material check in qsearch pruning

Passed simplification STC
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 47712 W: 12621 L: 12409 D: 22682 Elo +1.54
Ptnml(0-2): 224, 5349, 12480, 5597, 206
https://tests.stockfishchess.org/tests/view/67a1b4fb612069de394afc37

Passed rebased simplification LTC
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 188274 W: 47727 L: 47677 D: 92870 Elo +0.09
Ptnml(0-2): 171, 20429, 52867, 20519, 151
https://tests.stockfishchess.org/tests/view/67a2a761fedef70e42ac3300

closes https://github.com/official-stockfish/Stockfish/pull/5866

bench 2654242
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Disservin
Date: Wed Feb 5 18:52:28 2025 +0100
Timestamp: 1738777948

Show stdout/stderr in CI/CD tests

makes it easier to fix based on warnings shown with e.g. valgrind

closes https://github.com/official-stockfish/Stockfish/pull/5862

No functional change
see source
Windows x64 for Haswell CPUs
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: Tue Feb 4 23:08:43 2025 +0100
Timestamp: 1738706923

Fixes a wrongly combined merge conflict from the previous merge wave.

Passed STC:
https://tests.stockfishchess.org/tests/view/67a288aaeb183d11c65945f1
LLR: 2.99 (-2.94,2.94) <0.00,2.00>
Total: 51424 W: 13588 L: 13237 D: 24599 Elo +2.37
Ptnml(0-2): 223, 6039, 12860, 6344, 246

Passed LTC:
https://tests.stockfishchess.org/tests/view/67a28c0aeb183d11c6594609
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 54144 W: 13900 L: 13543 D: 26701 Elo +2.29
Ptnml(0-2): 42, 5881, 14870, 6236, 43

closes https://github.com/official-stockfish/Stockfish/pull/5863

Bench: 2345723
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
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: Tue Feb 4 21:37:11 2025 +0100
Timestamp: 1738701431

Reduce less for positions without tt move

Continuation of work on scaling.
In line with previous scaling patches this one massively reduces
reduction for moves that don't go thru lmr for position without a tt
move.

Passed VVLTC with STC bounds:
https://tests.stockfishchess.org/tests/view/679fd2450774dfd78deb12b2
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 74718 W: 19354 L: 19042 D: 36322 Elo +1.45
Ptnml(0-2): 5, 6724, 23595, 7024, 11

Passed VVLTC with LTC bounds:
https://tests.stockfishchess.org/tests/view/67a009930774dfd78deb2346
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 82638 W: 21587 L: 21212 D: 39839 Elo +1.58
Ptnml(0-2): 15, 7476, 25953, 7869, 6

closes https://github.com/official-stockfish/Stockfish/pull/5860

Bench: 2887850
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: Tue Feb 4 21:34:08 2025 +0100
Timestamp: 1738701248

VVLTC parameters tweak

Some notes:
- Both tests were conducted on top of #5848.
- Based on tuning suggestions, the extension for capturing the
previously moved piece was removed/simplified. (Developers can attempt
to reintroduce it post-merge if needed.)
- Initially, bonusScale = std::max(bonusScale, -2); was included but
later removed in the second test upon Viz's request, however, it was
nearly non-functional anyway.

Passed VVLTC under STC bounds:
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 31508 W: 8153 L: 7895 D: 15460 Elo +2.85
Ptnml(0-2): 1, 2747, 10005, 2995, 6
https://tests.stockfishchess.org/tests/view/679fdc7a0774dfd78deb1350

Passed VVLTC under LTC bounds:
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 55026 W: 14370 L: 14046 D: 26610 Elo +2.05
Ptnml(0-2): 7, 4957, 17262, 5279, 8
https://tests.stockfishchess.org/tests/view/679fec920774dfd78deb19b8

closes https://github.com/official-stockfish/Stockfish/pull/5856

Bench: 2757788
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
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: Tue Feb 4 21:30:54 2025 +0100
Timestamp: 1738701054

Increment cutoffCnt less often after fail high

Only increment when extension is less than 2 or it's a PvNode.

Tested vs #5851.

Failed STC:
LLR: -2.97 (-2.94,2.94) <0.00,2.00>
Total: 360064 W: 94546 L: 94271 D: 171247 Elo +0.27
Ptnml(0-2): 1835, 42826, 90314, 43343, 1714
https://tests.stockfishchess.org/tests/view/679f79cc0774dfd78deb1112

Passed LTC:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 443076 W: 113942 L: 113081 D: 216053 Elo +0.68
Ptnml(0-2): 480, 49076, 121579, 49909, 494
https://tests.stockfishchess.org/tests/view/679fa21b0774dfd78deb1178

Passed VLTC:
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 187184 W: 48098 L: 47495 D: 91591 Elo +1.12
Ptnml(0-2): 59, 19036, 54792, 19653, 52
https://tests.stockfishchess.org/tests/view/679fb6000774dfd78deb11e8

closes https://github.com/official-stockfish/Stockfish/pull/5855

Bench: 3018089
see source
Windows x64 for modern computers + AVX2
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: Tue Feb 4 21:28:49 2025 +0100
Timestamp: 1738700929

Do less aggressive pruning for higher movecounts

Move part of heuristic that makes reduction less before pruning stage.

Passed STC:
https://tests.stockfishchess.org/tests/view/679fdf1b0774dfd78deb13b3
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 47136 W: 12484 L: 12146 D: 22506 Elo +2.49
Ptnml(0-2): 211, 5472, 11866, 5806, 213

Passed LTC:
https://tests.stockfishchess.org/tests/view/679fe6790774dfd78deb1753
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 100536 W: 25837 L: 25383 D: 49316 Elo +1.57
Ptnml(0-2): 103, 10990, 27622, 11456, 97

closes https://github.com/official-stockfish/Stockfish/pull/5853

Bench: 3265587
see source
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Kenneth Lee
Date: Tue Feb 4 21:26:04 2025 +0100
Timestamp: 1738700764

Simplify cutoffCnt further

Based off [Simplify cutoffCnt](https://github.com/official-stockfish/Stockfish/commit/69be04d38e10003853e78e4aa2b32aa252a82850) commit

Original
[commit](https://github.com/kennethlee33/Stockfish/commit/a77a895c3b7460f86b11a3ddfe3528f5be1276b9)
adding extension condition seems to not be improving strength anymore

Passed STC:
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 54176 W: 14331 L: 14125 D: 25720 Elo +1.32
Ptnml(0-2): 261, 6340, 13676, 6554, 257
https://tests.stockfishchess.org/tests/view/679edb7c0774dfd78deb0eed

Passed LTC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 267198 W: 68148 L: 68179 D: 130871 Elo -0.04
Ptnml(0-2): 232, 30051, 73055, 30038, 223
https://tests.stockfishchess.org/tests/view/679ef2c70774dfd78deb0f43

closes https://github.com/official-stockfish/Stockfish/pull/5851

Bench: 3119355
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: Nonlinear2
Date: Tue Feb 4 21:24:06 2025 +0100
Timestamp: 1738700646

Simplify bonusScale formula

Passed STC:
https://tests.stockfishchess.org/tests/view/679ea7bc0774dfd78deb0d68
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 47680 W: 12575 L: 12364 D: 22741 Elo +1.54
Ptnml(0-2): 179, 5589, 12139, 5708, 225

Passed LTC:
https://tests.stockfishchess.org/tests/view/679eb7760774dfd78deb0dbb
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 314220 W: 80110 L: 80189 D: 153921 Elo -0.09
Ptnml(0-2): 265, 35121, 86420, 35036, 268

closes https://github.com/official-stockfish/Stockfish/pull/5849

Bench: 3161782
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Nonlinear2
Date: Tue Feb 4 21:22:08 2025 +0100
Timestamp: 1738700528

Reduce full depth search twice

Passed STC:
https://tests.stockfishchess.org/tests/view/679f429e0774dfd78deb10a5
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 71584 W: 18905 L: 18529 D: 34150 Elo +1.82
Ptnml(0-2): 302, 8372, 18081, 8722, 315

Passed LTC:
https://tests.stockfishchess.org/tests/view/679f72a00774dfd78deb1102
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 353952 W: 91007 L: 90024 D: 172921 Elo +0.96
Ptnml(0-2): 375, 39163, 96921, 40138, 379

closes https://github.com/official-stockfish/Stockfish/pull/5848

Bench: 3642363
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Disservin
Date: Tue Feb 4 21:18:01 2025 +0100
Timestamp: 1738700281

Disallow same option being added twice

Now exits during startup.

```
./stockfish
Stockfish dev-20250202-243c7c6a by the Stockfish developers (see AUTHORS file)
x1,5,0,10,0.5,0.0020
Option: "x1" was already added!
```

i.e. prevents and helps debug this case

```cpp
int x1 = 5;

TUNE(x1);
TUNE(x1);
```

closes https://github.com/official-stockfish/Stockfish/pull/5847

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: Shawn Xu
Date: Tue Feb 4 21:11:37 2025 +0100
Timestamp: 1738699897

Simplify depth increase condition further

Passed Non-regression STC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 51232 W: 13560 L: 13351 D: 24321 Elo +1.42
Ptnml(0-2): 183, 6075, 12920, 6226, 212
https://tests.stockfishchess.org/tests/view/679d7b2b0774dfd78deb043f

Passed Non-regression LTC (v. #5827):
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 172398 W: 44108 L: 44042 D: 84248 Elo +0.13
Ptnml(0-2): 122, 19207, 47489, 19245, 136
https://tests.stockfishchess.org/tests/view/679d7fb10774dfd78deb05d2

Passed Non-regression VLTC (v. #5827):
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 388540 W: 99314 L: 99464 D: 189762 Elo -0.13
Ptnml(0-2): 89, 40454, 113350, 40272, 105
https://tests.stockfishchess.org/tests/view/679da3be0774dfd78deb0ad4

closes https://github.com/official-stockfish/Stockfish/pull/5846

Bench: 2688175
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: Guenther Demetz
Date: Tue Feb 4 21:11:05 2025 +0100
Timestamp: 1738699865

Micro-optimization for SEE: remove a superfluous condition

This condition can never be true, it's superfluous.

It never triggers even with a bench 16 1 20 run.
To met the condition it would imply that the previous recapture was done
by a higher rated piece than a Queen.
This is only the case when the King recaptures and that's already
handled in line 1161: (return (attackers & ~pieces(stm)) ? res ^ 1).

closes https://github.com/official-stockfish/Stockfish/pull/5839

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 + SSSE3
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Robert Nurnberg @ elitebook
Date: Sun Feb 2 13:54:04 2025 +0100
Timestamp: 1738500844

Add cursed win checks to CI matetrack tests

This PR adds a run for the `matecheck.py` script from the matetrack repo
with the option `--syzygy50MoveRule false`.

The new tests guard against a re-introduction of the bugs recently fixed
by https://github.com/official-stockfish/Stockfish/pull/5814.

closes https://github.com/official-stockfish/Stockfish/pull/5829

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: Kenneth Lee
Date: Sun Feb 2 13:52:16 2025 +0100
Timestamp: 1738500736

Simplify extensions depth increase condition

Passed STC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 42784 W: 11198 L: 10979 D: 20607 Elo +1.78
Ptnml(0-2): 166, 5024, 10822, 5185, 195
https://tests.stockfishchess.org/tests/view/6795b6f8f6281b7d7b1869d6

Failed LTC:
LLR: -2.95 (-2.94,2.94) <-1.75,0.25>
Total: 283614 W: 72046 L: 72587 D: 138981 Elo -0.66
Ptnml(0-2): 241, 32097, 77647, 31606, 216
https://tests.stockfishchess.org/tests/view/6795cbb6f6281b7d7b186a07

Passed VLTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 59678 W: 15387 L: 15211 D: 29080 Elo +1.02
Ptnml(0-2): 23, 6169, 17273, 6357, 17
https://tests.stockfishchess.org/tests/view/6795c6dbf6281b7d7b1869f9

closes https://github.com/official-stockfish/Stockfish/pull/5827

Bench: 3088494
see source
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 Feb 2 13:49:54 2025 +0100
Timestamp: 1738500594

Silence clang-format issue

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
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 Feb 2 13:47:52 2025 +0100
Timestamp: 1738500472

Make pruning at ttpv nodes more aggressive

Continuation of work done by @FauziAkram and @Viren6 They had a series
of patches that decrease pruning for ttPv nodes - and it passed as a
gainer at lower time controls while revert passed as a gainer at higher
time controls.
So it's a logical continuation of this work that increases pruning for
ttPv nodes in hopes of scaling to longer TCs.

Fixed games STC:
https://tests.stockfishchess.org/tests/view/679ee3910774dfd78deb0efd
Elo: -4.98 ± 2.1 (95%) LOS: 0.0%
Total: 28584 W: 7229 L: 7639 D: 13716 Elo -4.98
Ptnml(0-2): 143, 3579, 7219, 3247, 104
nElo: -9.54 ± 4.0 (95%) PairsRatio: 0.90

Passed VVLTC with STC bounds:
https://tests.stockfishchess.org/tests/view/679d21f70774dfd78deaf553
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 323282 W: 83729 L: 83105 D: 156448 Elo +0.67
Ptnml(0-2): 37, 29842, 101269, 30446, 47

Passed VVLTC with LTC bounds:
https://tests.stockfishchess.org/tests/view/679e7a970774dfd78deb0cd3
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 113712 W: 29485 L: 29051 D: 55176 Elo +1.33
Ptnml(0-2): 13, 10376, 35640, 10818, 9

closes https://github.com/official-stockfish/Stockfish/pull/5844

Bench: 2964045
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 + SSSE3
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Shawn Xu
Date: Sun Feb 2 13:44:22 2025 +0100
Timestamp: 1738500262

Simplify Away Quadruple Extensions

Passed Non-regression LTC:
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 95856 W: 24551 L: 24404 D: 46901 Elo +0.53
Ptnml(0-2): 85, 10621, 26364, 10778, 80
https://tests.stockfishchess.org/tests/view/679a9aedae346be6da0eebd6

Passed Non-regression VLTC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 157536 W: 40000 L: 39921 D: 77615 Elo +0.17
Ptnml(0-2): 43, 16416, 45775, 16487, 47
https://tests.stockfishchess.org/tests/view/679aed8f51037ccaf3e30fbf

Passed Non-regression VVLTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 51598 W: 13345 L: 13172 D: 25081 Elo +1.16
Ptnml(0-2): 0, 4735, 16162, 4896, 6
https://tests.stockfishchess.org/tests/view/679d368b0774dfd78deb0163

closes https://github.com/official-stockfish/Stockfish/pull/5843

Bench: 2399312
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 Feb 2 13:43:32 2025 +0100
Timestamp: 1738500212

Tweak correction history factors

The values are taken from this tuning
https://tests.stockfishchess.org/tests/view/679c4e150774dfd78deaf376
which added also a new material correction history. The full tune
doesn't work but ignoring the new history results in this changes.

Passed STC:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 102368 W: 27057 L: 26638 D: 48673 Elo +1.42
Ptnml(0-2): 394, 12031, 25949, 12382, 428
https://tests.stockfishchess.org/tess/view/679d2ca70774dfd78deaf796

Passed LTC:
LLR: 2.96 (-2.94,2.94) <0.50,2.50>
Total: 55044 W: 14215 L: 13855 D: 26974 Elo +2.27
Ptnml(0-2): 43, 5956, 15172, 6300, 51
https://tests.stockfishchess.org/tests/view/679d30be0774dfd78deafda2

closes https://github.com/official-stockfish/Stockfish/pull/5841

Bench: 3068583
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: Daniel Monroe
Date: Sun Feb 2 13:39:47 2025 +0100
Timestamp: 1738499987

Simp probcut disable condition

Disable probcut check when we the ttValue is not at least probCutBeta,
regardless of tt depth.

Passed simplification STC
LLR: 2.92 (-2.94,2.94) <-1.75,0.25>
Total: 60896 W: 16030 L: 15835 D: 29031 Elo +1.11
Ptnml(0-2): 220, 7164, 15507, 7315, 242
https://tests.stockfishchess.org/tests/view/679c0a3251037ccaf3e3141e

Passed simplification LTC
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 76644 W: 19557 L: 19392 D: 37695 Elo +0.75
Ptnml(0-2): 50, 8486, 21104, 8613, 69
https://tests.stockfishchess.org/tests/view/679c380b0774dfd78deaf35c

closes https://github.com/official-stockfish/Stockfish/pull/5840

Bench: 3543770
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
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 Feb 2 13:37:47 2025 +0100
Timestamp: 1738499867

Make IIR for PvNodes less aggressive

In line with previous experiments on improving scaling of IIR.
Now it disables IIR for pv nodes with depth <= 2, so disallowing for it
to perform a qsearch dive.

Fixed games STC:
https://tests.stockfishchess.org/tests/view/679ae6a951037ccaf3e30fb3
Elo: -10.36 ± 2.5 (95%) LOS: 0.0%
Total: 20020 W: 4902 L: 5499 D: 9619 Elo -10.36
Ptnml(0-2): 128, 2653, 4976, 2194, 59

Passed VVLTC with STC bounds:
https://tests.stockfishchess.org/tests/view/67954f2e406a4efe9eb7d266
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 196758 W: 50725 L: 50258 D: 95775 Elo +0.82
Ptnml(0-2): 21, 18153, 61564, 18620, 21

Passed VVLTC with LTC bounds:
https://tests.stockfishchess.org/tests/view/6795a26bf6281b7d7b18698b
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 323092 W: 83679 L: 82857 D: 156556 Elo +0.88
Ptnml(0-2): 48, 29475, 101659, 30335, 29

closes https://github.com/official-stockfish/Stockfish/pull/5834

Bench: 3464332
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: Daniel Monroe
Date: Sun Feb 2 13:36:58 2025 +0100
Timestamp: 1738499818

Refactor prior reduction

Make index of reduction consistent with rest of Stack

closes https://github.com/official-stockfish/Stockfish/pull/5832

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Carlos Esparza
Date: Sun Feb 2 13:35:48 2025 +0100
Timestamp: 1738499748

Don't increase rule50 when doing null moves

also prefetch a bit earlier while we're at it

passed STC: https://tests.stockfishchess.org/tests/view/678c0860f4dc0a8b4ae8cf58
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 67328 W: 17608 L: 17418 D: 32302 Elo +0.98
Ptnml(0-2): 256, 7905, 17156, 8087, 260

passed LTC: https://tests.stockfishchess.org/tests/view/678c1a56f4dc0a8b4ae8cfb1
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 340896 W: 86577 L: 86685 D: 167634 Elo -0.11
Ptnml(0-2): 291, 38325, 93332, 38201, 299

closes https://github.com/official-stockfish/Stockfish/pull/5831

Bench: 1910281
see source

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