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Author SHA1 Message Date
FauziAkramandJoost VandeVondele e6d04b4ec5 VVLTC tune 
Passed VVLTC with stc bounds:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 21424 W: 5638 L: 5387 D: 10399
Ptnml(0-2): 2, 1925, 6607, 2176, 2
https://tests.stockfishchess.org/tests/view/69938fbcff782f8eeef612a9

Passed VVLTC with ltc bounds:
LLR: 2.96 (-2.94,2.94) <0.50,2.50>
Total: 33410 W: 8784 L: 8499 D: 16127
Ptnml(0-2): 5, 2968, 10474, 3253, 5
https://tests.stockfishchess.org/tests/view/69923ea872254723ef22c6fa

Verify Elo loss at STC:
LLR: -2.93 (-2.94,2.94) <-1.75,0.25>
Total: 17504 W: 4420 L: 4704 D: 8380
Ptnml(0-2): 56, 2259, 4420, 1947, 70
https://tests.stockfishchess.org/tests/view/69946e4186e4a3231411625b

closes https://github.com/official-stockfish/Stockfish/pull/6616

bench: 3074962
 2026-02-18 05:54:55 +01:00
Daniel MonroeandJoost VandeVondele 77d46ff61c Simplify probCutDepth term 
Passed STC
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 139392 W: 36003 L: 35897 D: 67492
Ptnml(0-2): 451, 16383, 35911, 16511, 440
https://tests.stockfishchess.org/tests/view/697ebb4d5f56030af97b5aa5

Passed LTC
LLR: 2.97 (-2.94,2.94) <-1.75,0.25>
Total: 266934 W: 67822 L: 67851 D: 131261
Ptnml(0-2): 175, 29579, 73955, 29616, 142
https://tests.stockfishchess.org/tests/view/6980e5a26362aee5c8a55398

closes https://github.com/official-stockfish/Stockfish/pull/6607

Bench: 2515956
 2026-02-13 07:22:36 +01:00
Daniel MonroeandJoost VandeVondele 91c6ea82aa Simplify malus formula 
Passed non-regression STC
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 51936 W: 13490 L: 13283 D: 25163
Ptnml(0-2): 161, 6128, 13184, 6333, 162
https://tests.stockfishchess.org/tests/view/698120e06362aee5c8a55412

Passed non-regression LTC
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 233772 W: 59502 L: 59499 D: 114771
Ptnml(0-2): 144, 25753, 65086, 25762, 141
https://tests.stockfishchess.org/tests/view/69827426889c3a4c31c8db52

closes https://github.com/official-stockfish/Stockfish/pull/6606

bench 2739355
 2026-02-13 07:15:35 +01:00
Daniel MonroeandJoost VandeVondele 89b4f457e0 Simplify malus decay formula 
Passed non-regression STC
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 93600 W: 24165 L: 24007 D: 45428
Ptnml(0-2): 325, 11021, 23958, 11163, 333
https://tests.stockfishchess.org/tests/view/698121d46362aee5c8a55414

Passed non-regression LTC
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 83232 W: 21236 L: 21077 D: 40919
Ptnml(0-2): 46, 9147, 23083, 9282, 58
https://tests.stockfishchess.org/tests/view/698336dc473df9d1d24a90e8

closes https://github.com/official-stockfish/Stockfish/pull/6600

Bench: 2666284
 2026-02-13 07:12:04 +01:00
lemteayandJoost VandeVondele b248d689a8 Add constexpr specifier back to conthist_bonuses 
Passed STC
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 60288 W: 15668 L: 15331 D: 29289
Ptnml(0-2): 159, 6490, 16532, 6781, 182
https://tests.stockfishchess.org/tests/view/698c835762a8f472da3a88e1

closes https://github.com/official-stockfish/Stockfish/pull/6611

No functional change
 2026-02-13 07:03:17 +01:00
Daniel MonroeandDisservin 21b0974f8d Simplify away main history default 
Passed non-regression STC
LLR: 2.97 (-2.94,2.94) <-1.75,0.25>
Total: 130752 W: 33725 L: 33605 D: 63422
Ptnml(0-2): 421, 15472, 33460, 15612, 411
https://tests.stockfishchess.org/tests/view/697eb9e35f56030af97b5a9e

Passed non-regression LTC
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 53352 W: 13697 L: 13509 D: 26146
Ptnml(0-2): 36, 5804, 14811, 5986, 39
https://tests.stockfishchess.org/tests/view/6980e5846362aee5c8a55396

closes https://github.com/official-stockfish/Stockfish/pull/6590

Bench: 2375860
 2026-02-08 15:22:29 +01:00
FauziAkramandDisservin f0d0c3ddd2 Simplify Triple Margin Formula 
Passed STC:
LLR: 3.01 (-2.94,2.94) <-1.75,0.25>
Total: 517472 W: 133271 L: 133575 D: 250626
Ptnml(0-2): 1628, 61366, 133032, 61102, 1608
https://tests.stockfishchess.org/tests/view/69590175d844c1ce7cc7e9a2

Passed LTC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 95430 W: 24242 L: 24098 D: 47090
Ptnml(0-2): 42, 10289, 26926, 10399, 59
https://tests.stockfishchess.org/tests/view/695f7f03ca95f52e4b85253c

Passed VVLTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 58828 W: 15299 L: 15135 D: 28394
Ptnml(0-2): 4, 5277, 18687, 5443, 3
https://tests.stockfishchess.org/tests/view/6961686c8709a8d27c0383f6

closes https://github.com/official-stockfish/Stockfish/pull/6546

Bench: 2570943
 2026-02-08 15:22:06 +01:00
Jakub CiolekandDisservin 73475b198d Remove prefetching in Position::do_null_move 
Passed non-regression STC, Hash=16:

LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 60704 W: 15709 L: 15522 D: 29473
Ptnml(0-2): 169, 6589, 16649, 6776, 169
https://tests.stockfishchess.org/tests/view/6963d381f6d2e8deff76918f

Passed non-regression STC SMP, Hash=512:

LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 313512 W: 80151 L: 80231 D: 153130
Ptnml(0-2): 376, 35492, 85111, 35390, 387
https://tests.stockfishchess.org/tests/view/696e1684e5a70879bd3fe38f

closes https://github.com/official-stockfish/Stockfish/pull/6545

No functional change
 2026-02-08 15:22:06 +01:00
Maxim MasiutinandJoost VandeVondele 542c30c292 Branchless correction history with to_sq_unchecked 
Add Move::to_sq_unchecked() that bypasses the is_ok() assertion,
for use in branchless code paths where invalid moves are masked out.

passed STC:
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 92384 W: 24052 L: 23665 D: 44667
Ptnml(0-2): 265, 10229, 24831, 10588, 279
https://tests.stockfishchess.org/tests/view/6974dfc798dc5fff1dba5b74

closes https://github.com/official-stockfish/Stockfish/pull/6569

No functional change
 2026-02-04 17:44:25 +01:00
Joost VandeVondele 0b9068d510 Fix integer overflow. 
scaledBonus can reach rather large values,
which lead to an int overflow as detected anematode using ubsan.
(see https://github.com/official-stockfish/Stockfish/issues/6505#issuecomment-3696988889)

It can be fixed by scaling nominator and denominator appropriately,
which doesn't change the bench, as long as there is no overflow.

First overflow/bench change happens at depth 26

closes https://github.com/official-stockfish/Stockfish/pull/6540

Bench: 2050811
 2026-01-15 22:13:26 +01:00
FauziAkramandJoost VandeVondele 9b8c5c9f75 Simplify fail high reduction formula 
Passed STC:
LLR: 2.97 (-2.94,2.94) <-1.75,0.25>
Total: 165792 W: 42849 L: 42768 D: 80175
Ptnml(0-2): 512, 19499, 42800, 19566, 519
https://tests.stockfishchess.org/tests/view/695cdd95912b7ff140de60c2

Passed LTC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 80448 W: 20619 L: 20459 D: 39370
Ptnml(0-2): 47, 8693, 22596, 8829, 59
https://tests.stockfishchess.org/tests/view/695f7e84ca95f52e4b852536

closes https://github.com/official-stockfish/Stockfish/pull/6535

bench: 2050811
 2026-01-10 15:47:11 +01:00
Jakub CiolekandJoost VandeVondele c27c1747e3 qsearch: prevent bestValue from going down 
The bestValue can sometimes go down. This happens 2% of the time or so.
This fix stops it from decreasing.

Failed gainer STC:
LLR: -2.94 (-2.94,2.94) <0.00,2.00>
Total: 146176 W: 37930 L: 37976 D: 70270
Ptnml(0-2): 480, 17422, 37366, 17304, 516
https://tests.stockfishchess.org/tests/view/6953be19572093c1986da66a

Passed Non-regression LTC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 257796 W: 65662 L: 65683 D: 126451
Ptnml(0-2): 164, 28247, 72087, 28246, 154
https://tests.stockfishchess.org/tests/view/69554ff0d844c1ce7cc7e333

closes https://github.com/official-stockfish/Stockfish/pull/6520
fixes https://github.com/official-stockfish/Stockfish/issues/6519

Bench: 2477446
 2026-01-06 12:08:08 +01:00
Joost VandeVondele 28844fc697 Update of the year 
Happy New Year!

closes https://github.com/official-stockfish/Stockfish/pull/6514

No functional change
 2026-01-01 16:17:38 +01:00
anematodeandJoost VandeVondele aeb3bf33a9 port get_changed_pieces to ARM NEON 
passed STC:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 71968 W: 18833 L: 18489 D: 34646
Ptnml(0-2): 192, 7310, 20643, 7640, 199
https://tests.stockfishchess.org/tests/view/69509e5c572093c1986d7a0a

closes https://github.com/official-stockfish/Stockfish/pull/6512

No functional change
 2026-01-01 16:04:43 +01:00
Michael ChalyandJoost VandeVondele ced9f69834 Adjust main history with every new root position 
this patch dampens down main history to 3/4 of it value for all possible moves
at the start of ID loop, making it partially refresh with every new root
position.

Passed STC:
https://tests.stockfishchess.org/tests/view/694e33ff572093c1986d7234
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 115520 W: 30164 L: 29735 D: 55621
Ptnml(0-2): 395, 13192, 30192, 13551, 430

Passed LTC:
https://tests.stockfishchess.org/tests/view/6950cbe6572093c1986d816c
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 63672 W: 16480 L: 16114 D: 31078
Ptnml(0-2): 46, 6524, 18329, 6892, 45

closes https://github.com/official-stockfish/Stockfish/pull/6504

bench 2710946
 2026-01-01 15:53:04 +01:00
Joost VandeVondele e0fb783c30 Fix incorrect initialization 
Fixes https://github.com/official-stockfish/Stockfish/issues/6505

Missing initialization seemingly resulting in side effects, as discussed in the issue.

Credit to Sopel for spotting the bug.

PR used as a testcase for CoPilot, doing the right thing https://github.com/official-stockfish/Stockfish/pull/6478#discussion_r2655467218

closes https://github.com/official-stockfish/Stockfish/pull/6511

No functional change
 2026-01-01 15:51:09 +01:00
anematodeDisservinMichael Chaly
 		969285fa5d Shared pawn history 
[Passed STC SMP](https://tests.stockfishchess.org/tests/view/694e506c572093c1986d7276):
```
LLR: 2.97 (-2.94,2.94) <0.00,2.00>
Total: 14992 W: 3924 L: 3653 D: 7415
Ptnml(0-2): 20, 1547, 4090, 1820, 19
```

[Passed LTC SMP](https://tests.stockfishchess.org/tests/live_elo/694ead61572093c1986d7365):
```
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 41146 W: 10654 L: 10342 D: 20150
Ptnml(0-2): 17, 3999, 12225, 4319, 13
```

[Passed a sanity check STC SMP post-refactoring](https://tests.stockfishchess.org/tests/view/69503997572093c1986d763a):
```
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 46728 W: 12178 L: 11863 D: 22687
Ptnml(0-2): 82, 5093, 12685, 5436, 68
```

(The large gain of the first STC was probably a fluke, and this result
is more reasonable!)

After shared correction history, Viz suggested we try sharing other
histories, especially `pawnHistory`. As far as we're aware, sharing
history besides correction history (like Caissa does) is novel. The
implementation follows the same pattern as shared correction history –
the size of the history table is scaled with
`next_power_of_two(threadsInNumaNode)` and the entry is prefetched in
`do_move`.

A bit of refactoring was done to accommodate this new history. Note that
we prefetch `&history->pawn_entry(*this)[pc][to]` rather than
`&history->pawn_entry(*this)` because unlike the other entries, each
entry contains multiple cache lines.

closes https://github.com/official-stockfish/Stockfish/pull/6498

Bench: 2503391

Co-authored-by: Michael Chaly <Vizvezdenec@gmail.com>
 2025-12-28 14:59:09 +01:00
Stefan GeschwentnerandDisservin 1780c1fd6e For expected ALL nodes scale up reduction with depth dependent factor. 
Passed STC:
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 141120 W: 36860 L: 36390 D: 67870
Ptnml(0-2): 470, 16441, 36314, 16819, 516
https://tests.stockfishchess.org/tests/view/694978e93c8768ca45072763

Passed LTC:
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 66576 W: 17078 L: 16700 D: 32798
Ptnml(0-2): 45, 7093, 18628, 7483, 39
https://tests.stockfishchess.org/tests/view/694bb608572093c1986d6ba6

closes https://github.com/official-stockfish/Stockfish/pull/6496

Bench: 2503391
 2025-12-28 14:55:55 +01:00
KazAppsandDisservin b2e60960b3 Fix nonPawnKey 
Fix incorrect nonPawnKey update

Passed non-reg SMP STC:
```
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 139424 W: 35792 L: 35690 D: 67942
Ptnml(0-2): 197, 15783, 37665, 15855, 212
```
https://tests.stockfishchess.org/tests/view/694b7b7e572093c1986d6b0d

Passed non-reg SMP LTC:
```
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 88880 W: 22863 L: 22718 D: 43299
Ptnml(0-2): 16, 8947, 26401, 9028, 48
```
https://tests.stockfishchess.org/tests/view/694d2ceb572093c1986d6fc8

fixes https://github.com/official-stockfish/Stockfish/issues/6492

closes https://github.com/official-stockfish/Stockfish/pull/6494

Bench: 2475788
 2025-12-28 14:55:47 +01:00
Daniel MonroeandDisservin 1047f844d1 Simplify doDeeperSearch 
Passed simplification STC
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 92096 W: 23888 L: 23728 D: 44480
Ptnml(0-2): 336, 10796, 23608, 10988, 320
https://tests.stockfishchess.org/tests/view/694b6b9d572093c1986d6ae0

Passed simplification LTC
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 50064 W: 12789 L: 12598 D: 24677
Ptnml(0-2): 24, 5350, 14103, 5521, 34
https://tests.stockfishchess.org/tests/view/694d49aa572093c1986d7021

closes https://github.com/official-stockfish/Stockfish/pull/6493

Bench: 2494221
 2025-12-28 14:53:12 +01:00
FauziAkramandDisservin cd3a837324 Refine reduction logic based on next-ply cutoff count 
Passed STC:
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 38208 W: 10076 L: 9754 D: 18378
Ptnml(0-2): 139, 4390, 9742, 4676, 157
https://tests.stockfishchess.org/tests/view/6945bb6446f342e1ec211d93

Passed LTC:
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 64086 W: 16529 L: 16157 D: 31400
Ptnml(0-2): 34, 6808, 17990, 7174, 37
https://tests.stockfishchess.org/tests/view/69479d303c8768ca45072446

closes https://github.com/official-stockfish/Stockfish/pull/6489

Bench: 2442415
 2025-12-28 14:49:19 +01:00
Taras VukandDisservin c475024be7 Incorporate statscore into history bonus 
Passed STC:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 80128 W: 20879 L: 20498 D: 38751
Ptnml(0-2): 274, 9318, 20496, 9705, 271
https://tests.stockfishchess.org/tests/view/6945d11f3c8768ca45072218

Passed LTC:
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 134298 W: 34497 L: 33983 D: 65818
Ptnml(0-2): 81, 14334, 37812, 14834, 88
https://tests.stockfishchess.org/tests/view/6947bf033c8768ca45072491

closes https://github.com/official-stockfish/Stockfish/pull/6488

Bench: 2325401
 2025-12-23 21:42:45 +01:00
FauziAkramandDisservin 4d4c6ebd02 Simplify doDeeperSearch formula 
Passed STC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 211776 W: 54939 L: 54911 D: 101926
Ptnml(0-2): 714, 24971, 54484, 25011, 708
https://tests.stockfishchess.org/tests/view/6938971875b70713ef796b70

Passed LTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 216774 W: 55346 L: 55326 D: 106102
Ptnml(0-2): 105, 23599, 60980, 23577, 126
https://tests.stockfishchess.org/tests/view/693fc91f46f342e1ec20f9f6

closes https://github.com/official-stockfish/Stockfish/pull/6486

Bench: 3267755
 2025-12-23 21:42:45 +01:00
Michael ChalyandDisservin 447f66acac Less penalty for quiet late moves that didn't beat the best move. 
This moves since they are late in move ordering probably already have pretty bad stats anyway.
Passed STC:
https://tests.stockfishchess.org/tests/view/6943bcd546f342e1ec210e25
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 96704 W: 25206 L: 24798 D: 46700
Ptnml(0-2): 357, 11244, 24767, 11602, 382
Passed LTC:
https://tests.stockfishchess.org/tests/view/6946a8723c8768ca450722f0
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 89814 W: 23193 L: 22770 D: 43851
Ptnml(0-2): 53, 9532, 25321, 9941, 60
bench 2717363

closes https://github.com/official-stockfish/Stockfish/pull/6485

Bench: 2791988
 2025-12-23 21:42:45 +01:00
anematodeandDisservin 1a67ccc72e Share correction history between threads 
We did quite a few tests because this is a pretty involved change with
unknown scaling behavior, but results are decent.

[STC 10+0.1 1th, non-regression](https://tests.stockfishchess.org/tests/live_elo/6941ce3b46f342e1ec210180)
```
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 83200 W: 21615 L: 21452 D: 40133
Ptnml(0-2): 247, 9064, 22844, 9169, 276
```

[STC 5+0.05 8th](https://tests.stockfishchess.org/tests/live_elo/693dc38346f342e1ec20f555)
```
LLR: 3.48 (-2.94,2.94) <0.00,2.00>
Total: 58536 W: 15067 L: 14688 D: 28781
Ptnml(0-2): 87, 6474, 15781, 6825, 101
```

[LTC 20+0.2 8th](https://tests.stockfishchess.org/tests/live_elo/693f2afb46f342e1ec20f847)
```
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 27716 W: 7211 L: 6925 D: 13580
Ptnml(0-2): 8, 2674, 8207, 2962, 7
```

[LTC 10+0.1 64th](https://tests.stockfishchess.org/tests/live_elo/694003aa46f342e1ec20fac4):
```
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 16918 W: 4439 L: 4182 D: 8297
Ptnml(0-2): 3, 1493, 5213, 1744, 6
```

[NUMA test, 5+0.05 256th](https://tests.stockfishchess.org/tests/view/6941ee4e46f342e1ec210203)
```
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 7124 W: 1910 L: 1678 D: 3536
Ptnml(0-2): 0, 560, 2211, 790, 1
```

[LTC 60+0.6 64th](https://tests.stockfishchess.org/tests/live_elo/6940a85346f342e1ec20fcde):
```
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 15504 W: 4045 L: 3826 D: 7633
Ptnml(0-2): 0, 1002, 5530, 1219, 1
```

Bonus (courtesy of Viz): The 1 double kill in this last test was master
blundering a cool mate in 3: https://lichess.org/jyNZuRl4

Basically the idea here is to share correction history between threads.
That way, T1 can use the correction values produced by T2, which already
searched positions with that pawn structure etc., so that T1 can search
more efficiently. The table size per thread is about the same, so we
shouldn't get a large increase in hash collisions; in fact, I'd expect a
lower collision rate overall.

Although I came up with and implemented the idea independently,
[Caissa](https://github.com/Witek902/Caissa) was the first engine to
implement corrhist sharing (and corrhist in the first place) – this idea
is not completely novel.

The table size is rounded to a power of two. In particular, it's `65536
* nextPowerOfTwo(threadCount)`. That way, the indexing operation becomes
an AND of the key bits with a mask, rather than something more expensive
(e.g., a `mul_hi64`-style approach or a modulo).

The updates are racy, like the TT, but because `entry` is hoisted into a
register, there's no risk of writing back a value that's out of the
designated range `[-D, D]`. Various attempts at rewriting using atomics
led to substantial slowdowns, so we begrudgingly ignored the functions
in thread sanitizer, but at some point we'd like to make this better.

We allocate one shared correction history per NUMA node, because the
penalty associated with crossing nodes is substantial – I get a 40% hit
with NPS=4 and 256 threads, which is intolerable. With separate tables
per NUMA node I get a 6% penalty for nodes per second, which isn't ideal
but apparently compensated for.

closes https://github.com/official-stockfish/Stockfish/pull/6478

Bench: 2690604

Co-authored-by: Disservin <disservin.social@gmail.com>
 2025-12-23 21:42:29 +01:00
AliceRoseliaandDisservin c467fe5ba4 Simplify futility pruning 
Passed non regression STC:
https://tests.stockfishchess.org/tests/view/693e642c46f342e1ec20f68d
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 107968 W: 28080 L: 27937 D: 51951
Ptnml(0-2): 381, 12708, 27626, 12925, 344

Passed non regression LTC:
https://tests.stockfishchess.org/tests/view/693ff10c46f342e1ec20fa6a
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 334266 W: 85271 L: 85370 D: 163625
Ptnml(0-2): 179, 36395, 94086, 36292, 181

closes https://github.com/official-stockfish/Stockfish/pull/6484

Bench: 2987379
 2025-12-21 15:43:32 +01:00
Daniel MonroeandDisservin b4b01d0ca2 Remove rootDepth condition in newDepth clamping 
Passed simplification STC
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 132256 W: 34462 L: 34347 D: 63447
Ptnml(0-2): 470, 15625, 33833, 15720, 480
https://tests.stockfishchess.org/tests/view/69325fe0a24a6df719fcca16

Passed simplification LTC
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 128220 W: 32503 L: 32392 D: 63325
Ptnml(0-2): 94, 13900, 35982, 14069, 65
https://tests.stockfishchess.org/tests/view/6934c2b3a24a6df719fcdf1e

closes https://github.com/official-stockfish/Stockfish/pull/6472

Bench: 2926903
 2025-12-21 15:43:32 +01:00
Daniel MonroeandDisservin 8449e5eb9d Remove non-functional term in isShuffling 
closes https://github.com/official-stockfish/Stockfish/pull/6462

No functional change
 2025-12-21 15:43:32 +01:00
FauziAkramandDisservin 5edfabd070 Fix Typo 
closes https://github.com/official-stockfish/Stockfish/pull/6436

No functional change
 2025-12-21 15:22:06 +01:00
Daniel MonroeandJoost VandeVondele 5297ba0a1a 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
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
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
 2025-12-01 17:35:34 +01:00
FauziAkramandDisservin c95386256e 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
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
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
 2025-11-30 21:58:35 +01:00
Shawn XuandDisservin 45d034fa50 Formatting fixups 
closes https://github.com/official-stockfish/Stockfish/pull/6446

No functional change
 2025-11-30 21:58:35 +01:00
pb00067andDisservin c73f21df97 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
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
Ptnml(0-2): 53, 11841, 33488, 11954, 57

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

Bench: 2941767
 2025-11-30 21:58:34 +01:00
Daniel MonroeandJoost VandeVondele d9fd516547 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
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
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
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
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
 2025-11-22 07:56:47 +01:00
Shawn XuandJoost VandeVondele 035cb146d4 Do more futility pruning 
closes https://github.com/official-stockfish/Stockfish/pull/6433

Bench: 2469519
 2025-11-17 14:03:02 +01:00
Timothy HerchenandJoost VandeVondele b083049fe0 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
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
 2025-11-17 13:24:32 +01:00
Robert NurnbergandJoost VandeVondele 4b71d8e202 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
 2025-11-14 17:38:55 +01:00
Daniel MonroeandJoost VandeVondele a191791f46 Clean up code and comments 
closes https://github.com/official-stockfish/Stockfish/pull/6416

No functional change
 2025-11-14 17:30:55 +01:00
AliceRoseliaandJoost VandeVondele 7b7a9485d6 Simplify indexing 
Removes 1 function (from_to) from the Move type, change them to simpler raw.
Remove the "and" use in the correction history structure calculation. Adjust
the indexing.

Passed simplification STC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 42880 W: 11327 L: 11113 D: 20440
Ptnml(0-2): 161, 4852, 11212, 5042, 173
https://tests.stockfishchess.org/tests/view/690593b8ea4b268f1fac1e8a

Passed simplification LTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 43560 W: 11276 L: 11079 D: 21205
Ptnml(0-2): 17, 4679, 12197, 4864, 23
https://tests.stockfishchess.org/tests/view/6906f819ea4b268f1fac216b

closes https://github.com/official-stockfish/Stockfish/pull/6391

Bench: 2523092
 2025-11-14 17:28:17 +01:00
FauziAkramandJoost VandeVondele df88db16c6 Simplify NMP reduction formula 
Passed STC:
LLR: 2.97 (-2.94,2.94) <-1.75,0.25>
Total: 178912 W: 46625 L: 46559 D: 85728
Ptnml(0-2): 540, 21167, 45975, 21235, 539
https://tests.stockfishchess.org/tests/view/69060677ea4b268f1fac1f25

Passed LTC:
LLR: 2.99 (-2.94,2.94) <-1.75,0.25>
Total: 140988 W: 36278 L: 36176 D: 68534
Ptnml(0-2): 82, 15520, 39215, 15568, 109
https://tests.stockfishchess.org/tests/view/6908bc32ea4b268f1fac288f

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

bench: 2959834
 2025-11-14 17:24:16 +01:00
Guenther DemetzandJoost VandeVondele 4784ff2b3b Unify do_move & do_null_move workload 
While being there also remove and unused assignment.

Tested for non-regression at STC:
https://tests.stockfishchess.org/tests/view/69060d81ea4b268f1fac1f36
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 94496 W: 24570 L: 24421 D: 45505
Ptnml(0-2): 264, 10145, 26275, 10306, 258

closes https://github.com/official-stockfish/Stockfish/pull/6383

no functional change
 2025-11-13 22:26:35 +01:00
Timothy HerchenandJoost VandeVondele fa4f05d3ef Don't copy around DirtyThreats 
The contents of DirtyThreats gets memcpyed twice for each call to do_move.
(Return value optimization doesn't apply to the do_move function itself because
it constructs a std::pair, so it gets copied; and the calls to reset also
require a copy.) This patch inserts the dirty info in place.

Sometimes the caller of do_move ignores the DirtyThreats info, so we pass in
scratch objects. I found that stack-allocating these scratch objects was bad on
Fishtest, so I begrudgingly put them in the Position struct. Both templating
the do_move function on whether dirty threats are needed and putting a
null-check branch for each use of dirty threats were slowdowns locally. Of
course, nothing prevents a future attempt at cleaning this up.

passed STC
LLR: 2.96 (-2.94,2.94) <0.00,2.00>
Total: 68448 W: 17770 L: 17418 D: 33260
Ptnml(0-2): 198, 7425, 18630, 7769, 202
https://tests.stockfishchess.org/tests/view/6914c01a7ca87818523318ba

closes https://github.com/official-stockfish/Stockfish/pull/6414

No functional change
 2025-11-13 22:17:03 +01:00
Daniel MonroeandJoost VandeVondele 7ac8e62219 Refine constant in correction history update 
Passed STC
LLR: 3.04 (-2.94,2.94) <0.00,2.00>
Total: 250112 W: 65277 L: 64635 D: 120200
Ptnml(0-2): 841, 29326, 64134, 29860, 895
https://tests.stockfishchess.org/tests/view/69096c46ea4b268f1fac2a39

Passed LTC
LLR: 2.96 (-2.94,2.94) <0.50,2.50>
Total: 142908 W: 37141 L: 36604 D: 69163
Ptnml(0-2): 100, 15478, 39742, 16053, 81
https://tests.stockfishchess.org/tests/view/690e7dfbec1d00d2c195c351

closes https://github.com/official-stockfish/Stockfish/pull/6405

bench 2613869
 2025-11-13 22:10:30 +01:00
+1
sscg13Joost VandeVondeleShawn XuTimothy HerchenViren6Yoshie2000rn5f107s2cj5716AliceRoseliaLinmiao XuDisservin
 		8e5392d79a Update NNUE architecture to SFNNv10 with Threat Inputs and net nn-49c1193b131c.nnue 
This commit introduces Full Threat Input features, which are a subset of Piece(Square)-Piece(Square) pairs. In any given position, the active features consist of pairs where the second piece’s square lies in the attack set of the first piece. This is an extremely simplified explanation that leaves out many details. The already-used HalfKAv2_hm feature set completes the input features.
Minor quantization changes have also been made.

The net nn-49c1193b131c.nnue was trained by vondele using the following setup: https://github.com/vondele/nettest/blob/7de71238e9b295e3f88ed7c9c5936af632c9b981/threats.yaml

A graphical version of an earlier scheme (with less refinement) that illustrates the core concepts can be found attached.
[NewInputs.pdf](https://github.com/user-attachments/files/23478441/NewInputs.pdf)

Further information, as well as a brief description of the history of development, can be found attached.
[Stockfish threat inputs PR summary.pdf](https://github.com/user-attachments/files/23478634/Stockfish.threat.inputs.PR.summary.pdf)

This has been a huge effort spanning over half a year, with the original [discussion thread](https://discord.com/channels/435943710472011776/1336647760388034610) reaching over 11k messages. Thanks to everyone who has contributed.

Monty PRs:
https://github.com/official-monty/Monty/pull/87 (Initial threat input PR)
https://github.com/official-monty/Monty/pull/114 (Fixed threat indexing to take into account colour correctly)
https://github.com/official-monty/Monty/pull/116 (i8 quantisation of weights whilst keeping calculations in i16)

Yukari commit:
https://github.com/yukarichess/yukari/commit/2d482c64a79cec03cf4987d5289334b9cdc737bc (Threat inputs merged)

Plentychess PRs:
https://github.com/Yoshie2000/PlentyChess/pull/400 (Threat inputs merged)
https://github.com/Yoshie2000/PlentyChess/pull/411 (Threat input weights quantised to i8)

Passed STC:
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 63424 W: 16956 L: 16591 D: 29877
Ptnml(0-2): 276, 7522, 15797, 7795, 322
https://tests.stockfishchess.org/tests/view/69105b3dec1d00d2c195c569

Passed LTC:
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 27876 W: 7417 L: 7110 D: 13349
Ptnml(0-2): 23, 3033, 7530, 3318, 34
https://tests.stockfishchess.org/tests/view/6910d817ec1d00d2c195c66e

Passed VVLTC (Hash accidentally set to 1/2 normal value for both sides):
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 12458 W: 3353 L: 3102 D: 6003
Ptnml(0-2): 0, 1106, 3767, 1355, 1
https://tests.stockfishchess.org/tests/view/69115a26ec1d00d2c195c7cd

This version has also passed non-regression LTC against the originally passed version:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 51144 W: 13086 L: 12903 D: 25155
Ptnml(0-2): 22, 5167, 15018, 5336, 29
https://tests.stockfishchess.org/tests/view/69138a317ca87818523314bf

LTC elo estimate on ARM:
1 patch     :    13.9    1.9  38296.5   73728    52
2 master    :     0.0   ----  35431.5   73728    48

closes https://github.com/official-stockfish/Stockfish/pull/6411

bench: 2626086

Co-authored-by: Shawn Xu <xu107288696@gmail.com>
Co-authored-by: Timothy Herchen <timothy.herchen@gmail.com>
Co-authored-by: Viren6 <94880762+Viren6@users.noreply.github.com>
Co-authored-by: Yoshie2000 <patrick.leonhardt@gmx.net>
Co-authored-by: Joost Vandevondele <Joost.VandeVondele@gmail.com>
Co-authored-by: rn5f107s2 <clemens.lerchl@gmail.com>
Co-authored-by: cj5716 <125858804+cj5716@users.noreply.github.com>
Co-authored-by: AliceRoselia <63040919+AliceRoselia@users.noreply.github.com>
Co-authored-by: Linmiao Xu <linmiao.xu@gmail.com>
Co-authored-by: Disservin <disservin.social@gmail.com>
 2025-11-12 10:49:39 +01:00
FauziAkramandJoost VandeVondele bc9f08731f Simplify Futility pruning formula 
Passed STC:
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 170112 W: 44266 L: 44193 D: 81653
Ptnml(0-2): 599, 20062, 43611, 20235, 549
https://tests.stockfishchess.org/tests/view/68f50b94637acd2a11e721ad

Passed LTC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 164658 W: 42393 L: 42318 D: 79947
Ptnml(0-2): 120, 18127, 45747, 18228, 107
https://tests.stockfishchess.org/tests/view/68fa6683637acd2a11e72ac3

closes https://github.com/official-stockfish/Stockfish/pull/6389

bench: 2351426
 2025-11-01 11:39:00 +01:00
Shawn XuandJoost VandeVondele cd7880c030 Simplify Corrhist Bonus 
Passed Non-regression STC:
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 187776 W: 48687 L: 48631 D: 90458
Ptnml(0-2): 570, 22327, 48090, 22279, 622
https://tests.stockfishchess.org/tests/view/68f58019637acd2a11e72233

Passed Non-regression LTC:
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 159378 W: 41027 L: 40946 D: 77405
Ptnml(0-2): 122, 17645, 44078, 17718, 126
https://tests.stockfishchess.org/tests/view/68fe7492637acd2a11e73090

closes https://github.com/official-stockfish/Stockfish/pull/6385

Bench: 2458738
 2025-11-01 11:36:33 +01:00
Shawn XuandJoost VandeVondele 0351652995 Simplify Pawn History Bonus 
Passed Non-regression STC:
LLR: 2.98 (-2.94,2.94) <-1.75,0.25>
Total: 122016 W: 31655 L: 31525 D: 58836
Ptnml(0-2): 388, 14317, 31474, 14435, 394
https://tests.stockfishchess.org/tests/view/68f57e66637acd2a11e7221d

Passed Non-regression LTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 81348 W: 21016 L: 20858 D: 39474
Ptnml(0-2): 45, 8793, 22841, 8949, 46
https://tests.stockfishchess.org/tests/view/68f9e2d9637acd2a11e72997

closes https://github.com/official-stockfish/Stockfish/pull/6382

Bench: 2370893
 2025-11-01 11:32:53 +01:00
Daniel MonroeandJoost VandeVondele c9a2aff485 Simplify correction update condition 
Passed non-regression STC
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 95136 W: 24722 L: 24564 D: 45850
Ptnml(0-2): 307, 11139, 24522, 11289, 311
https://tests.stockfishchess.org/tests/view/68e5034ea017f472e763dc5a

Passed non-regression LTC
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 256440 W: 65854 L: 65873 D: 124713
Ptnml(0-2): 144, 28287, 71375, 28272, 142
https://tests.stockfishchess.org/tests/view/68e71ae4a017f472e763e291

closes https://github.com/official-stockfish/Stockfish/pull/6375

bench 2216361
 2025-11-01 11:29:47 +01:00
Daniel MonroeandJoost VandeVondele 013d42914f Simplify static eval bonus 
Passed non-regression STC
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 176896 W: 45998 L: 45933 D: 84965
Ptnml(0-2): 609, 20845, 45451, 20958, 585
https://tests.stockfishchess.org/tests/view/68e5e48ba017f472e763dd21

Passed non-regression LTC
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 77682 W: 20046 L: 19884 D: 37752
Ptnml(0-2): 41, 8404, 21786, 8572, 38
https://tests.stockfishchess.org/tests/view/68ee71e328e6d77fcff9fd68

closes https://github.com/official-stockfish/Stockfish/pull/6374

bench 2101654
 2025-11-01 11:27:27 +01:00
Daniel MonroeandJoost VandeVondele fd3c563f57 Simplify r50 condition in cutoff 
Passed non-regression STC
LLR: 3.11 (-2.94,2.94) <-1.75,0.25>
Total: 114560 W: 29832 L: 29689 D: 55039
Ptnml(0-2): 332, 12302, 31869, 12445, 332
https://tests.stockfishchess.org/tests/view/68e38587fa806e2e8393d4a9

Passed non-regression LTC
LLR: 2.99 (-2.94,2.94) <-1.75,0.25>
Total: 256272 W: 65817 L: 65832 D: 124623
Ptnml(0-2): 137, 25528, 76817, 25521, 133
https://tests.stockfishchess.org/tests/view/68e69b47a017f472e763e065

closes https://github.com/official-stockfish/Stockfish/pull/6373

Bench: 2438327
 2025-11-01 11:20:23 +01:00