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Author SHA1 Message Date
pb00067
0f905b4e88 Preserve all moves in movepicker 
Simplifies method otherPieceTypesMobile quite a bit and makes it more
precise. More precise because capturesSearched list not always contains
all processed captures:
although extremely rare, it can happen that a 'good' capture get pruned
at step 14 and doesn't make it to capturesSearched. (functional change
at higher depths)

passed STC-simplification bounds
https://tests.stockfishchess.org/tests/view/68025974cd501869c6698153
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 273664 W: 15658 L: 15681 D: 242325
Ptnml(0-2): 166, 10368, 115802, 10315, 181

passed LTC-simplification bounds
https://tests.stockfishchess.org/tests/view/6804b86acd501869c6698673
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 96780 W: 24547 L: 24419 D: 47814
Ptnml(0-2): 30, 8466, 31286, 8562, 46

Applied changes requested by disservin & retested to be on the safe side

STC:
https://tests.stockfishchess.org/tests/view/6806110698cd372e3aea5919
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 107392 W: 27739 L: 27606 D: 52047
Ptnml(0-2): 266, 10867, 31306, 10982, 275

LTC:
https://tests.stockfishchess.org/tests/view/6806346198cd372e3aea5965
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 233484 W: 59106 L: 59103 D: 115275
Ptnml(0-2): 116, 22787, 70939, 22778, 122

closes https://github.com/official-stockfish/Stockfish/pull/6005

Bench: 1857323
 2025-05-13 20:23:43 +02:00
FauziAkram
94e6c0498f VVLTC Tune 
Passed VVLTC with LTC bounds:
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 12800 W: 3432 L: 3184 D: 6184
Ptnml(0-2): 1, 1098, 3954, 1346, 1
https://tests.stockfishchess.org/tests/view/680e255e3629b02d74b15d5e

Passed VVLTC with STC bounds:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 14402 W: 3865 L: 3625 D: 6912
Ptnml(0-2): 0, 1236, 4490, 1474, 1
https://tests.stockfishchess.org/tests/view/680e4dfb3629b02d74b15da6

Passed VVLTC third test (removing an unrelated change):
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 25584 W: 6670 L: 6398 D: 12516
Ptnml(0-2): 4, 2290, 7932, 2562, 4
https://tests.stockfishchess.org/tests/view/680e74223629b02d74b15def

closes https://github.com/official-stockfish/Stockfish/pull/6036

Bench: 1857323
 2025-04-27 20:47:47 +02:00
Daniel Monroe
af3692b2d0 Simplify second probcut to linear function of depth 
Passed non-regression STC
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 57472 W: 14962 L: 14765 D: 27745
Ptnml(0-2): 140, 6715, 14817, 6936, 128
https://tests.stockfishchess.org/tests/view/680df1063629b02d74b15b69

Passed non-regression LTC
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 88416 W: 22499 L: 22348 D: 43569
Ptnml(0-2): 31, 9565, 24874, 9698, 40
https://tests.stockfishchess.org/tests/view/680df3a93629b02d74b15b7d

closes https://github.com/official-stockfish/Stockfish/pull/6035

Bench: 1792000
 2025-04-27 20:31:40 +02:00
Michael Chaly
3e26d3acc7 Do more pruning in moves loop 
Effectively reverts one commit from some months ago.

Passed VVLTC SPRT with STC bounds
https://tests.stockfishchess.org/tests/view/680d39373629b02d74b156d7
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 405058 W: 104843 L: 104111 D: 196104
Ptnml(0-2): 35, 38029, 125672, 38755, 38

Passed VVLTC SPRT with LTC bounds
https://tests.stockfishchess.org/tests/view/680d1a3b3629b02d74b1563d
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 57032 W: 14917 L: 14588 D: 27527
Ptnml(0-2): 6, 5202, 17768, 5537, 3

closes https://github.com/official-stockfish/Stockfish/pull/6031

Bench: 1643819
 2025-04-27 20:28:22 +02:00
FauziAkram
267fd8a3d5 Tweak History Bonus 
Inspired by @Ergodice , who came up first with the idea.

Passed STC:
LLR: 2.96 (-2.94,2.94) <0.00,2.00>
Total: 18400 W: 4867 L: 4576 D: 8957
Ptnml(0-2): 52, 2052, 4714, 2317, 65
https://tests.stockfishchess.org/tests/view/68062a3c98cd372e3aea5959

Passed LTC:
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 454338 W: 116461 L: 115294 D: 222583
Ptnml(0-2): 198, 49139, 127346, 50270, 216
https://tests.stockfishchess.org/tests/view/6806347c98cd372e3aea5967

Passed VLTC non-reg:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 385970 W: 98401 L: 98546 D: 189023
Ptnml(0-2): 51, 38958, 115105, 38827, 44
https://tests.stockfishchess.org/tests/view/680cfe873629b02d74b155cf

closes https://github.com/official-stockfish/Stockfish/pull/6030

Bench: 1715817
 2025-04-27 20:14:38 +02:00
FauziAkram
e5aa4b48c6 Simplify Evasion Move Scoring 
Passed STC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 160256 W: 41432 L: 41348 D: 77476
Ptnml(0-2): 485, 19034, 41028, 19074, 507
https://tests.stockfishchess.org/tests/view/680d242c3629b02d74b15662

Passed LTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 103086 W: 26388 L: 26252 D: 50446
Ptnml(0-2): 41, 11174, 28982, 11300, 46
https://tests.stockfishchess.org/tests/view/680d47f83629b02d74b1571e

closes https://github.com/official-stockfish/Stockfish/pull/6029

Bench: 1937261
 2025-04-27 19:47:08 +02:00
FauziAkram
f98c178960 Improve quiet moves bonus 
Inspired by an old test by Peregrine.

Passed STC:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 453024 W: 117244 L: 116316 D: 219464
Ptnml(0-2): 1336, 53355, 116258, 54171, 1392
https://tests.stockfishchess.org/tests/view/680ccacc3629b02d74b15532

Passed LTC:
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 140550 W: 35990 L: 35462 D: 69098
Ptnml(0-2): 65, 15152, 39319, 15668, 71
https://tests.stockfishchess.org/tests/view/680d2ed73629b02d74b15691

closes https://github.com/official-stockfish/Stockfish/pull/6028

Bench: 1708152
 2025-04-27 19:45:37 +02:00
Myself
37cc2293ef Replace complex probcut function with a precomputed table. 
Passed non-regression STC:
https://tests.stockfishchess.org/tests/view/680de2683629b02d74b15b46
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 116000 W: 29864 L: 29742 D: 56394
Ptnml(0-2): 215, 11811, 33854, 11877, 243

closes https://github.com/official-stockfish/Stockfish/pull/6026

No functional change
 2025-04-27 19:45:00 +02:00
Shawn Xu
b0a7a34d3f Simplify malus calculation 
closes https://github.com/official-stockfish/Stockfish/pull/6024

No functional change
 2025-04-27 19:43:47 +02:00
Carlos Esparza
f0de8dc034 Simplify move ordering bonuses for putting piece en prise and escaping capture 
Now there is also a penalty for exposing knights and bishops to capture by a pawn.

Passed STC:
https://tests.stockfishchess.org/tests/view/68074379878abf56f9a0d5b1
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 96512 W: 24841 L: 24687 D: 46984
Ptnml(0-2): 294, 11336, 24835, 11504, 287

Passed LTC:
https://tests.stockfishchess.org/tests/view/6808954a878abf56f9a0d76d
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 221328 W: 56271 L: 56255 D: 108802
Ptnml(0-2): 131, 24149, 62071, 24199, 114

closes https://github.com/official-stockfish/Stockfish/pull/6023

Bench: 1778227
 2025-04-27 19:42:06 +02:00
Carlos Esparza
fda269a299 Introduce double incremental accumulator updates 
when we need to update an accumulator by two moves and the second move
captures the piece moved in the first move, we can skip computing the
middle accumulator and cancel a feature add with a feature remove to
save work.

Passed STC
https://tests.stockfishchess.org/tests/view/67f70b1c31d7cf8afdc45f51
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 72800 W: 18878 L: 18529 D: 35393
Ptnml(0-2): 160, 7711, 20374, 7930, 225

closes https://github.com/official-stockfish/Stockfish/pull/5988

No functional change
 2025-04-27 19:27:18 +02:00
Shawn Xu
4e49f8dff9 Clean up search 
* Correct IIR scaling comments
* Replace `(PvNode || cutNode)` with `!allNode`
* Consistent formatting for scaler tags
* Add comments to some recently-introduced LMR terms
* Add comments on PCM bonus tweaks

Passed Non-regression STC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 389472 W: 102457 L: 102622 D: 184393
Ptnml(0-2): 1676, 41887, 107798, 41676, 1699
https://tests.stockfishchess.org/tests/view/67a0ea670774dfd78deb23cd

closes https://github.com/official-stockfish/Stockfish/pull/5854

Bench: 1585741
 2025-04-27 19:26:02 +02:00
Michael Chaly
27428a61c2 Allow some nodes to spawn even deeper lmr searches 
This includes nodes that were PvNode on a previous ply and only for non cutNodes and movecounts < 8.

Passed STC:
https://tests.stockfishchess.org/tests/view/680cdf2e3629b02d74b15576
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 123552 W: 31979 L: 31539 D: 60034
Ptnml(0-2): 322, 14449, 31803, 14871, 331

Passed LTC:
https://tests.stockfishchess.org/tests/view/680cf09a3629b02d74b15599
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 114306 W: 29310 L: 28837 D: 56159
Ptnml(0-2): 51, 12247, 32090, 12708, 57

closes https://github.com/official-stockfish/Stockfish/pull/6022

bench: 1585741
 2025-04-26 22:40:41 +02:00
Michael Chaly
4b58079485 Simplify and cleanup futility pruning for child nodes 
This patch removes (eval - beta) / 8 addition and adjusts constants
accordingly, also moves every calculation into futility_margin function.

Passed STC:
https://tests.stockfishchess.org/tests/view/6806d00f878abf56f9a0d524
LLR: 2.99 (-2.94,2.94) <-1.75,0.25>
Total: 483456 W: 124592 L: 124860 D: 234004
Ptnml(0-2): 1419, 57640, 123927, 57274, 1468

Passed LTC:
https://tests.stockfishchess.org/tests/view/680cceb33629b02d74b1554c
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 263868 W: 67076 L: 67104 D: 129688
Ptnml(0-2): 155, 28893, 73846, 28905, 135

closes https://github.com/official-stockfish/Stockfish/pull/6021

bench: 1618439
 2025-04-26 22:38:14 +02:00
Myself
7e6a0c464b Check only if good see. 
Passed STC:
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 106400 W: 27863 L: 27444 D: 51093
Ptnml(0-2): 320, 12431, 27275, 12858, 316
https://tests.stockfishchess.org/tests/view/6806239498cd372e3aea5949

Passed LTC:
LLR: 2.96 (-2.94,2.94) <0.50,2.50>
Total: 420534 W: 107594 L: 106494 D: 206446
Ptnml(0-2): 197, 45541, 117722, 46579, 228
https://tests.stockfishchess.org/tests/view/6806b4b3878abf56f9a0d4fc

closes https://github.com/official-stockfish/Stockfish/pull/6020

bench: 1675758
 2025-04-26 22:33:49 +02:00
FauziAkram
5f32b3ed4b Remove unneeded return statement 
closes https://github.com/official-stockfish/Stockfish/pull/6013

No functional change
 2025-04-26 22:26:39 +02:00
breatn
f590767b91 Adaptive beta cut 
passed STC:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 197088 W: 51084 L: 50533 D: 95471
Ptnml(0-2): 547, 23201, 50577, 23592, 627
https://tests.stockfishchess.org/tests/view/680604d798cd372e3aea58fe

passed LTC
LLR: 2.96 (-2.94,2.94) <0.50,2.50>
Total: 127950 W: 32719 L: 32214 D: 63017
Ptnml(0-2): 69, 13825, 35673, 14348, 60
https://tests.stockfishchess.org/tests/view/6805eae498cd372e3aea588a

closes https://github.com/official-stockfish/Stockfish/pull/6012

bench 1579003
 2025-04-26 22:23:26 +02:00
FauziAkram
8b85290313 Remove manual stack alignment workaround for GCC < 9.3 
consequently using these old compilers will now error out.

closes https://github.com/official-stockfish/Stockfish/pull/6008

No functional change.
 2025-04-26 22:15:08 +02:00
Nonlinear2
0dcfe096d6 Increase full depth search reduction when cutNode 
In addition to the core patch, improve the use of `isTTMove`:

- this name was used to mean both `bestMove == ttData.move` and `move == ttData.move`, so i replaced the argument `isTTMove` of `update_all_stats` with `TTMove` directly.

- `ttData.move == move` was  still used in some places instead of `ss->isTTMove`. I replaced these to be more consistent.

Passed STC:
https://tests.stockfishchess.org/tests/view/68057b8f98cd372e3aea3472
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 38400 W: 10048 L: 9734 D: 18618
Ptnml(0-2): 102, 4360, 9956, 4686, 96

Passed LTC:
https://tests.stockfishchess.org/tests/view/68057f7c98cd372e3aea3842
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 312666 W: 79494 L: 78616 D: 154556
Ptnml(0-2): 144, 33809, 87563, 34659, 158

closes https://github.com/official-stockfish/Stockfish/pull/6007

Bench: 1623376
 2025-04-26 22:11:40 +02:00
Daniel Monroe
88a524c552 Tweak futility formula 
Passed STC
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 248448 W: 64344 L: 63718 D: 120386
Ptnml(0-2): 750, 29172, 63783, 29740, 779
https://tests.stockfishchess.org/tests/view/68056f5598cd372e3aea2901

Passed LTC
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 118824 W: 30358 L: 29874 D: 58592
Ptnml(0-2): 59, 12797, 33228, 13257, 71
https://tests.stockfishchess.org/tests/view/6805675698cd372e3aea20d0

closes https://github.com/official-stockfish/Stockfish/pull/6004

bench 1839796
 2025-04-26 22:06:18 +02:00
Stefan Geschwentner
7988de4aa3 Prefer discovered and double checks in capture ordering. 
Increase weight for captured piece value if also a discovered or double check.

Passed STC:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 142144 W: 36632 L: 36164 D: 69348
Ptnml(0-2): 429, 16470, 36788, 16974, 411
https://tests.stockfishchess.org/tests/view/68052d7498cd372e3ae9faaa

Passed LTC:
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 668328 W: 170837 L: 169238 D: 328253
Ptnml(0-2): 308, 72010, 187990, 73487, 369
https://tests.stockfishchess.org/tests/view/68053c9398cd372e3aea043b

closes https://github.com/official-stockfish/Stockfish/pull/6003

Bench: 1636625
 2025-04-26 22:01:34 +02:00
FauziAkram
f6b0d53a99 Re-adding the 5th continuation history 
the two simplifications (#5992 and  #5978) are strongly correlated.

Passed STC:
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 98016 W: 25415 L: 25008 D: 47593
Ptnml(0-2): 291, 11509, 25005, 11908, 295
https://tests.stockfishchess.org/tests/view/6802774fcd501869c6698168

Passed LTC:
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 588588 W: 150073 L: 148633 D: 289882
Ptnml(0-2): 281, 63615, 165078, 65023, 297
https://tests.stockfishchess.org/tests/view/6804cbdacd501869c66987dc

closes https://github.com/official-stockfish/Stockfish/pull/6002

Bench: 1783315
 2025-04-26 21:58:46 +02:00
Michael Chaly
449a8b017e Do second step of shallower search 
Specifically if lmr depth is not lower than new depth and value is really bad.

Passed STC:
https://tests.stockfishchess.org/tests/view/6805444898cd372e3aea0494
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 77664 W: 20136 L: 19762 D: 37766
Ptnml(0-2): 214, 9006, 20039, 9338, 235

Passed LTC:
https://tests.stockfishchess.org/tests/view/680549b298cd372e3aea05ac
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 115458 W: 29447 L: 28971 D: 57040
Ptnml(0-2): 62, 12357, 32421, 12821, 68

closes https://github.com/official-stockfish/Stockfish/pull/6001

bench: 1515501
 2025-04-26 21:52:36 +02:00
Shawn Xu
4176ad7b0a simplify risk tolerance 
Passed Non-regression STC:
LLR: 2.98 (-2.94,2.94) <-1.75,0.25>
Total: 73408 W: 19028 L: 18844 D: 35536
Ptnml(0-2): 201, 8709, 18743, 8807, 244
https://tests.stockfishchess.org/tests/view/68051f3698cd372e3ae9f63a

Passed Non-regression LTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 91236 W: 23193 L: 23045 D: 44998
Ptnml(0-2): 34, 9908, 25599, 10030, 47
https://tests.stockfishchess.org/tests/view/6805239498cd372e3ae9fa41

closes https://github.com/official-stockfish/Stockfish/pull/6000

bench 1864632
 2025-04-26 21:49:38 +02:00
Shawn Xu
16cd38dba1 Tweak TT Move Reduction by TT Move History 
Passed STC:
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 62496 W: 16197 L: 15844 D: 30455
Ptnml(0-2): 200, 7234, 16011, 7619, 184
https://tests.stockfishchess.org/tests/view/67f7fa9b31d7cf8afdc4609c

Passed LTC:
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 400470 W: 102068 L: 101012 D: 197390
Ptnml(0-2): 201, 43207, 112347, 44295, 185
https://tests.stockfishchess.org/tests/view/67f927b0cd501869c66975e0

Passed VVLTC Non-regression:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 125394 W: 32408 L: 32304 D: 60682
Ptnml(0-2): 3, 11702, 39188, 11796, 8
https://tests.stockfishchess.org/tests/view/6804c215cd501869c66986b9

closes https://github.com/official-stockfish/Stockfish/pull/5998

bench 1760988
 2025-04-26 21:43:11 +02:00
Shawn Xu
b915ed702a remove StateInfo::next 
unused.

closes https://github.com/official-stockfish/Stockfish/pull/5997

no functional change
 2025-04-26 21:37:17 +02:00
Joost VandeVondele
f2507d0562 Add x86-64-avxvnni in CI 
will result in the corresponding binaries being available for download

closes https://github.com/official-stockfish/Stockfish/pull/5990

No functional change
 2025-04-26 21:34:26 +02:00
Shawn Xu
f273eea71f Remove non-functional accumulator reset 
Passed Non-regression STC:
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 219360 W: 56600 L: 56583 D: 106177
Ptnml(0-2): 582, 23419, 61620, 23518, 541
https://tests.stockfishchess.org/tests/view/67fad20dcd501869c669780f

closes https://github.com/official-stockfish/Stockfish/pull/5986

no functional change
 2025-04-26 21:30:01 +02:00
Joost VandeVondele
f9459e4c8e Use matching llvm-profdata 
when using multiple clang compilers in parallel, it is necessary to use
a matching llvm-profdata, as the profile data format may change between
versions. To use the proper llvm-profdata binary, the one in the same directory
as the compiler is used. This allows for code like:

```bash
echo "Compiling clang"
for comp in clang++-11 clang++-12 clang++-13 clang++-14  clang++-15  clang++-16  clang++-17 clang++-18 clang++-19 clang++-20
do
   make -j profile-build CXX=$comp COMP=clang >& out.compile.$comp
   mv stockfish stockfish.$comp
done
```

after installing the required versions with the automatic installation script (https://apt.llvm.org/)

closes https://github.com/official-stockfish/Stockfish/pull/5958

No functional change
 2025-04-26 21:25:18 +02:00
Daniel Monroe
3d18ad719b Skip 5th continuation history 
Passed simplification STC
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 70208 W: 18098 L: 17914 D: 34196
Ptnml(0-2): 199, 8300, 17907, 8514, 184
https://tests.stockfishchess.org/tests/view/67ed889b31d7cf8afdc451cb

Passed simplification LTC
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 485004 W: 122703 L: 122956 D: 239345
Ptnml(0-2): 288, 53162, 135805, 53009, 238
https://tests.stockfishchess.org/tests/view/67ee810231d7cf8afdc452ea

closes https://github.com/official-stockfish/Stockfish/pull/5992

Bench: 1715901
 2025-04-18 14:32:26 +02:00
Guenther Demetz
698c069bba Move node increment inside do_move function 
Move node increment inside do_move function so that we can centralize
the increment into a single point.

closes https://github.com/official-stockfish/Stockfish/pull/5989

No functional change
 2025-04-18 14:32:26 +02:00
Shawn Xu
2b4926e091 Simplify TT Move History 
Part 1 passed Non-regression STC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 195552 W: 50394 L: 50349 D: 94809
Ptnml(0-2): 581, 23222, 50122, 23273, 578
https://tests.stockfishchess.org/tests/view/67eb6ea831d7cf8afdc44c30

Part 2 passed Non-regression STC:
LLR: 2.92 (-2.94,2.94) <-1.75,0.25>
Total: 181664 W: 46786 L: 46727 D: 88151
Ptnml(0-2): 517, 21403, 46974, 21380, 558
https://tests.stockfishchess.org/tests/view/67eb6f3331d7cf8afdc44c33

Passed Non-regression LTC:
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 155454 W: 39496 L: 39412 D: 76546
Ptnml(0-2): 77, 16950, 43580, 17052, 68
https://tests.stockfishchess.org/tests/view/67eee76531d7cf8afdc45358

Passed Non-regression VLTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 118266 W: 30263 L: 30148 D: 57855
Ptnml(0-2): 11, 11844, 35309, 11957, 12
https://tests.stockfishchess.org/tests/view/67f2414a31d7cf8afdc45760

closes https://github.com/official-stockfish/Stockfish/pull/5987

Bench: 1792850
 2025-04-18 14:32:26 +02:00
pb00067
d2d046c2a4 Improve stalemate detection during search 
Currently SF’s quiescence search like most alpha-beta based engines
doesn’t verify for stalemate because doing it each leaf position is to
expensive and costs elo. However in certain positions this creates a
blindspot for SF, not recognizing soon enough that the opponent can
reach a stalemate by sacrifycing his last mobile heavy piece(s). This
tactical motif & it’s measure are similar to zugzwang & verification
search: the measure itself does not gain elo, but prevents SF from
loosing/drawing games in an awkward way.

The fix consists of 3 measures:

1. Make qsearch verify for stalemate on transitions to pure KP-material
   for the side to move with our last Rook/Queen just been captured. In
    fact this is the scenario where stalemate happens with highest
    frequency. The stalemate-verification itself is optimized by merely
    checking for pawn pushes & king mobility (captures were already
    tried by qssearch)

2. Another culprit for the issue figured out to be SEE based pruning for
   checks in step 14. Here often the move forcing the stalemate (or
   forcing the opponent to not retake) get pruned away and it need to
   much time to reach enough depth. To encounter this we verify
   following conditions:

-   a) side to move is happy with a draw (alpha < 0)
-   b) we are about to sacrify our last heavy & unique mobile piece in
    this position.
-   c) this piece doesn’t move away from our kingring giving the king a
    new square to move.
     When all 3 conditions meet we don’t prune the move, because there
     is a good chance that capturing the piece means stalemate.

3. Store terminal nodes (mates & stalemates) in TT with higher depth
   than searched depth. This prevents SF from:
- reanalyzing the node  (=trying to generate legal moves) in vain at
  each iterative deepening step.
- overwriting an already correct draw-evaluation from a previous shallow
  normal search by a qsearch which doesn’t recognize stalemate and might
  store a verry erratic evaluation.
 This is due to the 4 constant in the TT-overwrite condition: d -
 DEPTH_ENTRY_OFFSET + 2 * pv > depth8 – 4 which allows qs to override
 entries made by normal searches with depth <=4.
This 3hrd measure however is not essential for fixing the issue, but
tests (one of vdv & one  of mine) seem to suggest that this measure
brings some small benefit.

Another other position where SF benefits from this fix is for instance
Position FEN 8/8/8/1B6/6p1/8/3K1Ppp/3N2kr w - - 0 1 bm f4 +M9

P.S.: Also this issue higly depends on the used net, how good the net is
at evaluate such mobility restricted positions. SF16 was pretty good in
solving 2rr4/5pBk/PqP3p1/1N3pPp/1PQ1bP1P/8/3R4/R4K2 b - - 0 40 bm Rxc6
(< 1 second) while SF16_1 with introduction of the dual net needs about
1,5 minutes and SF17.1 requires 3 minutes to find the drawing move Rxc6.

P.S.2: Using more threads produces indeterminism & using high hash
pressure makes SF reevaluate explored positions more often which makes
it more likely to solve the position. To have stable meaningful results
I tested therfore with one single thread and low hash pressure.

Preliminary LTC test at 30k games
https://tests.stockfishchess.org/tests/view/67ece7a931d7cf8afdc44e18 Elo: 0.04 ± 2.0 (95%) LOS: 51.7%
Total: 24416 W: 6226 L: 6223 D: 11967
Ptnml(0-2): 12, 2497, 7185, 2504, 10
nElo: 0.09 ± 4.4 (95%) PairsRatio: 1.00

Passed LTC no-regression sprt
https://tests.stockfishchess.org/tests/view/67ee8e4631d7cf8afdc452fb
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 401556 W: 101612 L: 101776 D: 198168
Ptnml(0-2): 152, 42241, 116170, 42049, 166

closes https://github.com/official-stockfish/Stockfish/pull/5983
fixes https://github.com/official-stockfish/Stockfish/issues/5899

Bench: 1721673
 2025-04-18 14:32:26 +02:00
FauziAkram
44efbaddea Simplify bonusScale calculation 
Allowing this specific term to potentially become negative for low depth
values is ok, because the overall `bonusScale` is explicitly ensured to
be non-negative a few lines later: bonusScale = std::max(bonusScale, 0);

Passed STC:
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 164928 W: 42446 L: 42368 D: 80114
Ptnml(0-2): 497, 19551, 42306, 19597, 513
https://tests.stockfishchess.org/tests/view/67debf0b8888403457d8736c

Passed LTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 234942 W: 59539 L: 59537 D: 115866
Ptnml(0-2): 113, 25639, 65964, 25643, 112
https://tests.stockfishchess.org/tests/view/67e2e1c48888403457d87768

closes https://github.com/official-stockfish/Stockfish/pull/5979

Bench: 1933843
 2025-04-18 14:32:26 +02:00
Daniel Monroe
904a016396 Don't use 5th continuation history in move ordering 
Passed simplification STC
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 136960 W: 35374 L: 35262 D: 66324
Ptnml(0-2): 420, 16214, 35049, 16428, 369
https://tests.stockfishchess.org/tests/view/67e6d0ae6682f97da2178ee5

Passed simplification LTC
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 233016 W: 59063 L: 59059 D: 114894
Ptnml(0-2): 113, 25430, 65421, 25428, 116
https://tests.stockfishchess.org/tests/view/67e9f7fb31d7cf8afdc44ad4

closes https://github.com/official-stockfish/Stockfish/pull/5978

Bench: 1842721
 2025-04-18 14:32:26 +02:00
FauziAkram
5f8e67a544 Remove combineLast3 optimization 
Passed non-reg STC 1st:
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 67328 W: 17296 L: 17118 D: 32914
Ptnml(0-2): 158, 7095, 19011, 7211, 189
https://tests.stockfishchess.org/tests/view/67e6c2796682f97da2178ebe

Passed non-reg STC 2nd:
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 92288 W: 23885 L: 23734 D: 44669
Ptnml(0-2): 213, 10039, 25518, 10132, 242
https://tests.stockfishchess.org/tests/view/67ed6a2d31d7cf8afdc45190

closes https://github.com/official-stockfish/Stockfish/pull/5975

Bench: 1875196
 2025-04-18 14:32:26 +02:00
mstembera
8d2eef2b1e Fix fused() all controll paths should return a value. 
closes https://github.com/official-stockfish/Stockfish/pull/5973

No functional change
 2025-04-18 14:32:26 +02:00
AliceRoselia
2af64d581b Update AUTHORS 
closes https://github.com/official-stockfish/Stockfish/pull/5972

No functional change
 2025-04-18 14:32:19 +02:00
FauziAkram
cf8b3637a0 Improve futility pruning 
Adding a small term to the futility calculation that depends on eval - beta.
Refactored to a simpler form.

Passed STC:
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 74176 W: 19323 L: 18954 D: 35899
Ptnml(0-2): 226, 8576, 19117, 8941, 228
https://tests.stockfishchess.org/tests/view/67e6b0946682f97da2178eaf

Passed LTC:
LLR: 2.96 (-2.94,2.94) <0.50,2.50>
Total: 135090 W: 34499 L: 33983 D: 66608
Ptnml(0-2): 79, 14403, 38040, 14969, 54
https://tests.stockfishchess.org/tests/view/67e757cc6682f97da2178f62

closes https://github.com/official-stockfish/Stockfish/pull/5970

Bench: 1875196
 2025-04-18 14:32:19 +02:00
Disservin
bb3eaf8def Add cstddef header 
Fix missing header for std::size_t reported on discord.

closes https://github.com/official-stockfish/Stockfish/pull/5968

No functional change
 2025-04-18 14:32:19 +02:00
mstembera
1577fa0470 Simplify Forward and Backward 
Forward and Backward are not independent so simplify to a bool.

Cleanup some MSVC warnings like "warning C4267: 'argument': conversion
from 'size_t' to 'int', possible loss of data" Other minor formatting
stuff.

This is a rebase of https://github.com/official-stockfish/Stockfish/pull/5912

closes https://github.com/official-stockfish/Stockfish/pull/5967

No functional change
 2025-04-18 14:32:19 +02:00
Daniel Monroe
fb6a3e04ec Simply use non_pawn_material rather than summing tuned terms 
Passed simplification STC
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 136576 W: 35285 L: 35175 D: 66116
Ptnml(0-2): 410, 16179, 34997, 16295, 407
https://tests.stockfishchess.org/tests/view/67e5dc736682f97da2178da6

Passed rebased simplification LTC
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 85482 W: 21812 L: 21658 D: 42012
Ptnml(0-2): 34, 9260, 24022, 9368, 57
https://tests.stockfishchess.org/tests/view/67e852cb31d7cf8afdc44966

closes https://github.com/official-stockfish/Stockfish/pull/5965

Bench: 2006483
 2025-04-18 14:32:19 +02:00
Daniel Samek
15f34560f2 Update AUTHORS 
closes https://github.com/official-stockfish/Stockfish/pull/5964

No functional change
 2025-04-18 14:32:13 +02:00
Disservin
7beff18ef0 Retire Acc Pointer 
Since @xu-shawn's refactor the acc pointer has become a bit unnecessary,
we can achieve the same behavior by using the dimension size to get the
right accumulator from the `AccumulatorState`. I think the acc pointer
has become a bit of a burden required to be passed through multiple
different functions together with the necessary templating required.

Passed Non-Regression STC:
https://tests.stockfishchess.org/tests/view/67ed600f31d7cf8afdc45183
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 279744 W: 72037 L: 72082 D: 135625
Ptnml(0-2): 673, 29918, 78767, 29809, 705

closes https://github.com/official-stockfish/Stockfish/pull/5942

No functional change
 2025-04-18 13:54:09 +02:00
Shawn Xu
d7c04a9429 Introduce TT Move History Double Extensions 
Passed VVLTC w/ STC bounds:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 74918 W: 19436 L: 19120 D: 36362
Ptnml(0-2): 6, 6890, 23354, 7200, 9
https://tests.stockfishchess.org/tests/view/67e4a1088888403457d878bb

Passed VVLTC w/ LTC bounds:
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 111706 W: 29050 L: 28619 D: 54037
Ptnml(0-2): 13, 10218, 34959, 10651, 12
https://tests.stockfishchess.org/tests/view/67d6877c517865b4a2dfd36b

STC Elo Estimate:
Elo: 1.26 ± 2.0 (95%) LOS: 88.8%
Total: 30000 W: 7855 L: 7746 D: 14399
Ptnml(0-2): 104, 3531, 7630, 3622, 113
nElo: 2.44 ± 3.9 (95%) PairsRatio: 1.03
https://tests.stockfishchess.org/tests/view/67eacb8c31d7cf8afdc44b99

closes https://github.com/official-stockfish/Stockfish/pull/5961

Bench: 1887897
 2025-04-02 17:53:05 +02:00
Daniel Samek
d942e13398 Less fail high cnt in the condition 
Passed STC:
https://tests.stockfishchess.org/tests/view/67e027538888403457d87535
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 164000 W: 42535 L: 42034 D: 79431
Ptnml(0-2): 478, 19228, 42113, 19677, 504

Passed LTC:
https://tests.stockfishchess.org/tests/view/67e3c21b8888403457d87808
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 139176 W: 35500 L: 34975 D: 68701
Ptnml(0-2): 54, 15038, 38898, 15525, 73

closes https://github.com/official-stockfish/Stockfish/pull/5960

Bench: 1921404
 2025-04-02 17:52:38 +02:00
Daniel Monroe
3d61f932cb Squash out post-lmr bonus variable 
Squash out bonus variable for post-lmr now that the bonus is constant.

closes https://github.com/official-stockfish/Stockfish/pull/5953

No functional change
 2025-04-02 17:43:40 +02:00
mstembera
ed89817f62 Various cleanups 
Various simplifications, cleanups, consistancy improvements, and warning
mitigations.

Passed Non-Regression STC:
https://tests.stockfishchess.org/tests/view/67e7dd2d6682f97da2178fd8
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 386848 W: 99593 L: 99751 D: 187504
Ptnml(0-2): 1024, 41822, 107973, 41498, 1107

closes https://github.com/official-stockfish/Stockfish/pull/5948

No functional change
 2025-04-02 17:43:14 +02:00
mstembera
1a395f1b56 Remove pawn_attacks_bb() 
Generalize attacks_bb() to handle pawns and remove pawn_attacks_bb()

https://tests.stockfishchess.org/tests/view/67e9496231d7cf8afdc44a2e
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 134688 W: 34660 L: 34553 D: 65475
Ptnml(0-2): 298, 14619, 37462, 14608, 357

closes https://github.com/official-stockfish/Stockfish/pull/5947

No functional change
 2025-04-02 17:39:40 +02:00
Shawn Xu
d2cb927a04 Simplify TT cutoff conthist updates 
Passed Non-regression STC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 86304 W: 22251 L: 22084 D: 41969
Ptnml(0-2): 250, 10214, 22123, 10249, 316
https://tests.stockfishchess.org/tests/view/67db60cd8c7f315cc372aae7

Passed Non-regression LTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 199158 W: 50655 L: 50617 D: 97886
Ptnml(0-2): 103, 21579, 56182, 21607, 108
https://tests.stockfishchess.org/tests/view/67dcdc5b8c7f315cc372ac12

closes https://github.com/official-stockfish/Stockfish/pull/5945

Bench: 2069191
 2025-04-02 17:37:02 +02:00