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.

!! latest version !!


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: Timothy Herchen
Date: Wed Dec 3 12:32:29 2025 +0100
Timestamp: 1764761549

fix missing condition

Fixes a bug in https://github.com/official-stockfish/Stockfish/pull/6453
https://github.com/official-stockfish/Stockfish/commit/abd835dcbc3a28481224f6253b00b7420d062513
The modifications to the DirtyThreats bitboards should only happen if PutPiece is true.
This somehow didn't affect bench at the default parameters.

Reference AVX2:
./stockfish.killdeer-fix.avx2 bench 64 1 23
Nodes searched : 178140156
Nodes/second : 1503152

before patch:
./stockfish.master.avx512icl bench 64 1 23
Nodes searched : 218349728
Nodes/second : 1743450

after patch:
./stockfish.killdeer-fix.avx512icl bench 64 1 23
Nodes searched : 178140156
Nodes/second : 1727520

passed STC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 39328 W: 10293 L: 10080 D: 18955 Elo +1.88
Ptnml(0-2): 113, 4306, 10629, 4487, 129
https://tests.stockfishchess.org/tests/view/692fb2d8b23dfeae38d01c81

closes https://github.com/official-stockfish/Stockfish/pull/6463

Bench: 2912398
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: Daniel Monroe
Date: Mon Dec 1 17:35:34 2025 +0100
Timestamp: 1764606934

Move hindsight reductions above cutoffs

Passed STC
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 52640 W: 13701 L: 13361 D: 25578 Elo +2.24
Ptnml(0-2): 168, 6143, 13356, 6487, 166
https://tests.stockfishchess.org/tests/view/6918dc407ca8781852332339

Passed LTC
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 207690 W: 53187 L: 52520 D: 101983 Elo +1.12
Ptnml(0-2): 93, 22515, 57994, 23118, 125
https://tests.stockfishchess.org/tests/view/6919dd307ca87818523324c7

closes https://github.com/official-stockfish/Stockfish/pull/6448

Bench: 2912398
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: Timothy Herchen
Date: Mon Dec 1 17:26:50 2025 +0100
Timestamp: 1764606410

Improve update_piece_threats

passed on avx512ICL:
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 30240 W: 8026 L: 7726 D: 14488 Elo +3.45
Ptnml(0-2): 95, 3235, 8171, 3513, 106
https://tests.stockfishchess.org/tests/view/69281d9ab23dfeae38cfeeb8

passed on generic architectures:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 73184 W: 19183 L: 18821 D: 35180 Elo +1.72
Ptnml(0-2): 258, 7988, 19744, 8338, 264
https://tests.stockfishchess.org/tests/view/6928ba11b23dfeae38cff276

subsequent cleanups tested as:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 72480 W: 18678 L: 18502 D: 35300 Elo +0.84
Ptnml(0-2): 242, 7925, 19718, 8125, 230
https://tests.stockfishchess.org/tests/view/692a26adb23dfeae38cff566

We add an argument noRaysContaining, which skips all discoveries which contain
all bits in the argument; if the argument is from | to, then this will
eliminate the discovery. Separately, on AVX512ICL we can speed up the
computation of DirtyThreats by moving from a pop_lsb loop to a vector
extraction with vpcompressb. See PR for details.

closes https://github.com/official-stockfish/Stockfish/pull/6453

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: Joost VandeVondele
Date: Sun Nov 30 21:58:35 2025 +0100
Timestamp: 1764536315

Update main network to nn-2962dca31855.nnue

trained with https://github.com/vondele/nettest/blob/dd921672bd4ad8eb09fa45248078450857e81884/threats.yaml

on top off and tested against https://github.com/official-stockfish/Stockfish/pull/6452

passed STC
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 130720 W: 34028 L: 33570 D: 63122 Elo +1.22
Ptnml(0-2): 435, 15348, 33384, 15710, 483
https://tests.stockfishchess.org/tests/view/69294539b23dfeae38cff3ad

passed LTC
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 51144 W: 13140 L: 12794 D: 25210 Elo +2.35
Ptnml(0-2): 38, 5370, 14408, 5720, 36
https://tests.stockfishchess.org/tests/view/692a9c37b23dfeae38cffa4f

closes https://github.com/official-stockfish/Stockfish/pull/6457

Bench: 2823033
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: KazApps
Date: Sun Nov 30 21:58:35 2025 +0100
Timestamp: 1764536315

Update AUTHORS (KazApps)

closes https://github.com/official-stockfish/Stockfish/pull/6454

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: Joost VandeVondele
Date: Sun Nov 30 21:58:35 2025 +0100
Timestamp: 1764536315

Update main network to nn-87a9d7857d88.nnue

trained with https://github.com/vondele/nettest/blob/842d95177f882c0e9b5262247c38d8fcb3e0f3db/threats.yaml

passed STC:
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 114880 W: 30291 L: 29851 D: 54738 Elo +1.33
Ptnml(0-2): 499, 13547, 28947, 13909, 538
https://tests.stockfishchess.org/tests/view/6923ec4bba083df4ca63dd39

passed LTC:
LLR: 2.97 (-2.94,2.94) <0.50,2.50>
Total: 113268 W: 29115 L: 28634 D: 55519 Elo +1.48
Ptnml(0-2): 114, 12295, 31340, 12766, 119
https://tests.stockfishchess.org/tests/view/6925cd01b23dfeae38cfe134

closes https://github.com/official-stockfish/Stockfish/pull/6452

Bench: 3028457
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 Nov 30 21:58:35 2025 +0100
Timestamp: 1764536315

Simplify the highBestMoveEffort formula in Time management

Passed STC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 22272 W: 5885 L: 5655 D: 10732 Elo +3.59
Ptnml(0-2): 76, 2329, 6108, 2535, 88
https://tests.stockfishchess.org/tests/view/69244d07ba083df4ca63e02b

Passed LTC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 48690 W: 12405 L: 12221 D: 24064 Elo +1.31
Ptnml(0-2): 29, 4755, 14597, 4931, 33
https://tests.stockfishchess.org/tests/view/6924de9aba083df4ca63e327

closes https://github.com/official-stockfish/Stockfish/pull/6451

No functional change
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: Timothy Herchen
Date: Sun Nov 30 21:58:35 2025 +0100
Timestamp: 1764536315

Fix msvc macro

closes https://github.com/official-stockfish/Stockfish/pull/6449

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: Sun Nov 30 21:58:35 2025 +0100
Timestamp: 1764536315

Formatting fixups

closes https://github.com/official-stockfish/Stockfish/pull/6446

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: pb00067
Date: Sun Nov 30 21:58:34 2025 +0100
Timestamp: 1764536314

Fix for SF getting stuck during search (issue #5023)

Among several passed similar versions this is the simpliest one.

Passed STC non-regression
https://tests.stockfishchess.org/tests/view/691f3b4aacb6dbdf23d07d11
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 126368 W: 32607 L: 32489 D: 61272 Elo +0.32
Ptnml(0-2): 408, 13974, 34298, 14100, 404

Passed LTC non-regression
https://tests.stockfishchess.org/tests/view/69209712acb6dbdf23d0836a
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 114786 W: 29097 L: 28976 D: 56713 Elo +0.37
Ptnml(0-2): 53, 11841, 33488, 11954, 57

closes https://github.com/official-stockfish/Stockfish/pull/6447

Bench: 2941767
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: Carlos Esparza
Date: Sun Nov 30 21:45:14 2025 +0100
Timestamp: 1764535514

Some more work on FullThreats::make_index

[Passed STC](https://tests.stockfishchess.org/tests/live_elo/691fc321acb6dbdf23d07e4b):

```
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 215360 W: 55651 L: 55108 D: 104601 Elo +0.88
Ptnml(0-2): 520, 22399, 61290, 22960, 511
```

This PR is on top of ces42's work so I'll rebase if that PR changes.
Essentially, it comprises my adjustments to `make_index` that remained
unmerged before threat inputs was finalized.

The unsigned intermediate variables let us skip a bunch of useless sign
extensions (because Square and Piece inherit from `int8_t`, and C/C++
semantics require narrow integers to be promoted to `int` before doing
arithmetic on them). Additionally, by removing the special usage of
`offsets[][64]` and `[65]` the indexing becomes more efficient. (This
usage was a temporary hack from sscg anyway, so I think he'll like that
it's gone.) Finally, the `sf_assume` condition was fixed so that it
actually makes a difference to the compiler.

The speedup is fairly nice locally (combining both ces42's and these changes):

```
Result of 100 runs
==================
base (...kfish.master) = 1691982 +/- 1907
test (./stockfish ) = 1714349 +/- 1789
diff = +22367 +/- 2465

speedup = +0.0132
P(speedup > 0) = 1.0000
```

closes https://github.com/official-stockfish/Stockfish/pull/6445

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: Shawn Xu
Date: Sun Nov 30 21:43:54 2025 +0100
Timestamp: 1764535434

Simplify Incremental Updates

Passed Non-regression STC:
LLR: 3.03 (-2.94,2.94) <-1.75,0.25>
Total: 277856 W: 71575 L: 71611 D: 134670 Elo -0.05
Ptnml(0-2): 842, 30719, 75836, 30695, 836
https://tests.stockfishchess.org/tests/view/69169dc17ca8781852331d76

Supersedes #6430

closes https://github.com/official-stockfish/Stockfish/pull/6434

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: Sun Nov 30 21:41:51 2025 +0100
Timestamp: 1764535311

Simplify Accumulator Updates

Passed Non-regression STC:
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 146848 W: 37915 L: 37820 D: 71113 Elo +0.22
Ptnml(0-2): 415, 16159, 40186, 16244, 420
https://tests.stockfishchess.org/tests/view/691772217ca878185233202b

closes https://github.com/official-stockfish/Stockfish/pull/6421

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: Daniel Monroe
Date: Sat Nov 22 07:56:47 2025 +0100
Timestamp: 1763794607

Post-NNUEv10 tune

Tune search parameters after the switch to NNUEv10.

The change is neutral at STC but increases with the TC. The main changes are more aggressive corrections, futility pruning, and extensions.

Failed STC
LLR: -2.96 (-2.94,2.94) <0.00,2.00>
Total: 108320 W: 27616 L: 27719 D: 52985 Elo -0.33
Ptnml(0-2): 332, 12833, 27884, 12828, 283
https://tests.stockfishchess.org/tests/view/69212e623b03dd3a060e6114

Passed LTC
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 43272 W: 11117 L: 10788 D: 21367 Elo +2.64
Ptnml(0-2): 20, 4543, 12180, 4874, 19
https://tests.stockfishchess.org/tests/view/692130813b03dd3a060e6123

Passed VLTC
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 22714 W: 5840 L: 5581 D: 11293 Elo +3.96
Ptnml(0-2): 2, 2152, 6795, 2401, 7
https://tests.stockfishchess.org/tests/view/6921387b3b03dd3a060e6191

Passed VLTC SMP
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 11868 W: 3142 L: 2896 D: 5830 Elo +7.20
Ptnml(0-2): 0, 1007, 3676, 1249, 2
https://tests.stockfishchess.org/tests/view/69212e953b03dd3a060e611b

closes https://github.com/official-stockfish/Stockfish/pull/6444

bench 2907929
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: Mon Nov 17 14:03:02 2025 +0100
Timestamp: 1763384582

Do more futility pruning

closes https://github.com/official-stockfish/Stockfish/pull/6433

Bench: 2469519
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: Joost VandeVondele
Date: Mon Nov 17 14:00:33 2025 +0100
Timestamp: 1763384433

Update main net to nn-c0ae49f08b40.nnue

Trained using the recipe https://github.com/vondele/nettest/blob/d39f72420504e474a716b9977c1380541a7b482e/threats.yaml

fix CI check for negative evals.

fix format

passed STC:
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 84032 W: 21876 L: 21490 D: 40666 Elo +1.60
Ptnml(0-2): 239, 9821, 21553, 10121, 282
https://tests.stockfishchess.org/tests/view/6914b81e7ca87818523318aa

passed LTC:
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 126420 W: 32429 L: 31927 D: 62064 Elo +1.38
Ptnml(0-2): 56, 13748, 35118, 14214, 74
https://tests.stockfishchess.org/tests/view/6916c1277ca8781852331dd8

closes https://github.com/official-stockfish/Stockfish/pull/6431

Bench: 2513286
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: Joost VandeVondele
Date: Mon Nov 17 13:57:53 2025 +0100
Timestamp: 1763384273

Fix format

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: Andreas Matthies
Date: Mon Nov 17 13:37:55 2025 +0100
Timestamp: 1763383075

Cleanup benchmark

Avoid unnecessary consecutive ucinewgame commands in benchmark setup.
Remove measuring time and nodes in speedtest warmup.

closes https://github.com/official-stockfish/Stockfish/pull/6427

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: Joost VandeVondele
Date: Mon Nov 17 13:36:11 2025 +0100
Timestamp: 1763382971

Silence warning

for systems without shared memory support

Fixes https://github.com/official-stockfish/Stockfish/issues/6425

closes https://github.com/official-stockfish/Stockfish/pull/6426

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: Carlos Esparza
Date: Mon Nov 17 13:34:45 2025 +0100
Timestamp: 1763382885

inline make_index() and avoid templating perspective

combination of two patches.

pass perspective as argument
passed STC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 52832 W: 13725 L: 13528 D: 25579 Elo +1.30
Ptnml(0-2): 154, 5756, 14412, 5927, 167
https://tests.stockfishchess.org/tests/view/69162e307ca8781852331c6a

inline make_index
passed STC:
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 68768 W: 17786 L: 17607 D: 33375 Elo +0.90
Ptnml(0-2): 187, 7591, 18694, 7680, 232
https://tests.stockfishchess.org/tests/view/6916859e7ca8781852331d36

closes https://github.com/official-stockfish/Stockfish/pull/6429

No functional change
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: Timothy Herchen
Date: Mon Nov 17 13:24:32 2025 +0100
Timestamp: 1763382272

Use non-locking operations for nodes count and tbHits

fetch_add and friends must produce a locking instruction because they guarantee
consistency in the presence of multiple writers. Because only one thread ever
writes to nodes and tbHits, we may use relaxed load and store to emit regular
loads and stores (on both x86-64 and arm64), while avoiding undefined behavior
and miscounting nodes.

Credit must go to Arseniy Surkov of Reckless (codedeliveryservice) for
uncovering this performance gotcha.

failed yellow as a gainer on fishtest:
LLR: -2.95 (-2.94,2.94) <0.00,2.00>
Total: 219616 W: 57165 L: 57105 D: 105346 Elo +0.09
Ptnml(0-2): 732, 24277, 59720, 24357, 722
https://tests.stockfishchess.org/tests/view/69086abfea4b268f1fac2809

potential small speedup on large core system:
```
==== master ====
1 Nodes/second : 294269736
2 Nodes/second : 295217629
Average (over 2): 294743682
==== patch ====
1 Nodes/second : 299003603
2 Nodes/second : 298111320
Average (over 2): 298557461
```

closes https://github.com/official-stockfish/Stockfish/pull/6392

No functional change
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: Shawn Xu
Date: Fri Nov 14 17:43:44 2025 +0100
Timestamp: 1763138624

Fix undefined behavior

C++ standard does not define `uint8_t` as an allowed pointer alias type. Despite
`uint8_t` being `unsigned char` on most platforms, this is not enforced by the standard.

https://eel.is/c++draft/basic.lval#11
https://stackoverflow.com/a/16138470

closes https://github.com/official-stockfish/Stockfish/pull/6420

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: Robert Nurnberg
Date: Fri Nov 14 17:38:55 2025 +0100
Timestamp: 1763138335

Allow time checking after each DTZ probe

This PR allows for time checking within Tablebases::rank_root_moves(). The
principal application for now is syzygy_extend_pv().

In the past, Stockfish suffered some time losses at e.g. TCEC when the HDD with
the DTZ tables was too slow for the chosen move overhead setting, see #5894.

```
> ./fastchess -engine name="patch" cmd=./stockfish.patch -engine name="master" cmd=./stockfish.master -each tc=10+0.1 option.SyzygyPath=/disk1/syzygy/3-4-5-6/WDL:/disk2/syzygy/3-4-5-6/DTZ -draw movenumber=34 movecount=8 score=20 -openings file=UHO_Lichess_4852_v1.epd format=epd -rounds 50 -repeat -concurrency 16
...
Results of patch vs master (10+0.1, 1t, 16MB, UHO_Lichess_4852_v1.epd):
Elo: 59.64 +/- 35.35, nElo: 117.61 +/- 68.10
LOS: 99.96 %, DrawRatio: 56.00 %, PairsRatio: 4.50
Games: 100, Wins: 34, Losses: 17, Draws: 49, Points: 58.5 (58.50 %)
Ptnml(0-2): [0, 4, 28, 15, 3], WL/DD Ratio: 0.87
--------------------------------------------------

Player: master
Timeouts: 19
Crashed: 0

Finished match
```

closes https://github.com/official-stockfish/Stockfish/pull/6422

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: Fri Nov 14 17:32:17 2025 +0100
Timestamp: 1763137937

Pass accumulator caches by reference

closes https://github.com/official-stockfish/Stockfish/pull/6416

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: Daniel Monroe
Date: Fri Nov 14 17:30:55 2025 +0100
Timestamp: 1763137855

Clean up code and comments

closes https://github.com/official-stockfish/Stockfish/pull/6416

No functional change
see source

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