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
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Tomasz Sobczyk
Date: Mon Nov 2 19:41:17 2020 +0100
Timestamp: 1604342477

Optimize affine transform for SSSE3 and higher targets.

A non-functional speedup. Unroll the loops going over
the output dimensions in the affine transform layers by
a factor of 4 and perform 4 horizontal additions at a time.
Instead of doing naive horizontal additions on each vector
separately use hadd and shuffling between vectors to reduce
the number of instructions by using all lanes for all stages
of the horizontal adds.

passed STC of the initial version:
LLR: 2.95 (-2.94,2.94) {-0.25,1.25}
Total: 17808 W: 1914 L: 1756 D: 14138 Elo +3.08
Ptnml(0-2): 76, 1330, 5948, 1460, 90
https://tests.stockfishchess.org/tests/view/5f9d516f6a2c112b60691da3

passed STC of the final version after cleanup:
LLR: 2.95 (-2.94,2.94) {-0.25,1.25}
Total: 16296 W: 1750 L: 1595 D: 12951 Elo +3.30
Ptnml(0-2): 72, 1192, 5479, 1319, 86
https://tests.stockfishchess.org/tests/view/5f9df5776a2c112b60691de3

closes https://github.com/official-stockfish/Stockfish/pull/3203

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
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: mstembera
Date: Sun Nov 1 08:02:40 2020 +0100
Timestamp: 1604214160

Update default net to nn-cb26f10b1fd9.nnue

Result of https://tests.stockfishchess.org/tests/view/5f9a06796a2c112b60691c0f tuning.

STC
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 53712 W: 5776 L: 5561 D: 42375 Elo +1.39
Ptnml(0-2): 253, 4282, 17604, 4431, 286
https://tests.stockfishchess.org/tests/view/5f9c7bbc6a2c112b60691d4d

LTC
LLR: 2.97 (-2.94,2.94) {0.25,1.25}
Total: 80184 W: 4007 L: 3739 D: 72438 Elo +1.16
Ptnml(0-2): 58, 3302, 33130, 3518, 84
https://tests.stockfishchess.org/tests/view/5f9d01f06a2c112b60691d87

closes https://github.com/official-stockfish/Stockfish/pull/3209

bench: 3517795
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: syzygy1
Date: Wed Oct 28 23:40:37 2020 +0100
Timestamp: 1603924837

Do not skip non-recapture ttMove when in check

The qsearch() MovePicker incorrectly skips a non-recapture ttMove
when in check (if depth <= DEPTH_QS_RECAPTURES). This is clearly not
intended and can cause qsearch() to return a mate score when there
is no mate. Introduced in cad300c and 6596f0e, as observed by
joergoster in #3171 and #3198.

This PR fixes the bug by not skipping the non-recapture ttMove when in check.

Passed non-regression STC:
https://tests.stockfishchess.org/tests/view/5f9867ea6a2c112b60691b10
LLR: 2.98 (-2.94,2.94) {-1.25,0.25}
Total: 27112 W: 2943 L: 2842 D: 21327 Elo +1.29
Ptnml(0-2): 127, 2170, 8878, 2237, 144

Passed non-regression LTC:
https://tests.stockfishchess.org/tests/view/5f9967326a2c112b60691bb0
LLR: 2.99 (-2.94,2.94) {-0.75,0.25}
Total: 18392 W: 807 L: 738 D: 16847 Elo +1.30
Ptnml(0-2): 9, 655, 7802, 718, 12

closes https://github.com/official-stockfish/Stockfish/pull/3199
closes https://github.com/official-stockfish/Stockfish/pull/3198

Bench: 3870606
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: SFisGOD
Date: Wed Oct 28 08:13:34 2020 +0100
Timestamp: 1603869214

Update default net to nn-2eb2e0707c2b.nnue

Optimization of the net weights of the 32 x 32 layer (1024 parameters) and net biases of the 512 x 32 layer (32 parameters) using SPSA.

Tuning of 32 x 32 Layer (800,000 games, 5 seconds time control):
https://tests.stockfishchess.org/tests/view/5f942040d3978d7e86f1aa05

Tuning of 512 x 32 Layer (80,000 games, 20 seconds time control):
https://tests.stockfishchess.org/tests/view/5f8f926d2c92c7fe3a8c608b

STC:
LLR: 2.96 (-2.94,2.94) {-0.25,1.25}
Total: 17336 W: 1918 L: 1754 D: 13664 Elo +3.29
Ptnml(0-2): 79, 1344, 5672, 1480, 93
https://tests.stockfishchess.org/tests/view/5f9882346a2c112b60691b34

LTC:
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 37304 W: 1822 L: 1651 D: 33831 Elo +1.59
Ptnml(0-2): 27, 1461, 15501, 1640, 23
https://tests.stockfishchess.org/tests/view/5f98a4b36a2c112b60691b40

closes https://github.com/official-stockfish/Stockfish/pull/3201

Bench: 3403528
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: FauziAkram
Date: Wed Oct 28 08:11:29 2020 +0100
Timestamp: 1603869089

Bishop Pawns based on Files

Passed STC:
https://tests.stockfishchess.org/tests/view/5f8cc8145a4eacb45305da3c
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 132544 W: 27795 L: 27328 D: 77421 Elo +1.22
Ptnml(0-2): 2756, 15558, 29272, 15835, 2851

Passed LTC:
https://tests.stockfishchess.org/tests/view/5f8df614bacb75a4f9a4721e
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 169608 W: 23257 L: 22622 D: 123729 Elo +1.30
Ptnml(0-2): 1408, 16316, 48758, 16877, 1445

closes https://github.com/official-stockfish/Stockfish/pull/3194

Bench: 4067106
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: syzygy1
Date: Thu Oct 22 20:50:16 2020 +0200
Timestamp: 1603392616

More incremental accumulator updates

This patch was inspired by c065abd which updates the accumulator,
if possible, based on the accumulator of two plies back if
the accumulator of the preceding ply is not available.

With this patch we look back even further in the position history
in an attempt to reduce the number of complete recomputations.
When we find a usable accumulator for the position N plies back,
we also update the accumulator of the position N-1 plies back
because that accumulator is most likely to be helpful later
when evaluating positions in sibling branches.
By not updating all intermediate accumulators immediately,
we avoid doing too much work that is not certain to be useful.
Overall, roughly 2-3% speedup.

This patch makes the code more specific to the net architecture,
changing input features of the net will require additional changes
to the incremental update code as discussed in the PR #3193 and #3191.

Passed STC:
https://tests.stockfishchess.org/tests/view/5f9056712c92c7fe3a8c60d0
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 10040 W: 1116 L: 968 D: 7956 Elo +5.12
Ptnml(0-2): 42, 722, 3365, 828, 63

closes https://github.com/official-stockfish/Stockfish/pull/3193

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
Windows 32
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: Thu Oct 22 20:18:12 2020 +0200
Timestamp: 1603390692

Add net as dependency of config

cleaner output and error message if the server is down and the net is not available.

closes https://github.com/official-stockfish/Stockfish/pull/3188

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
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: xoto10
Date: Thu Oct 22 20:08:15 2020 +0200
Timestamp: 1603390095

Reduce big time spikes by reducing PV re-searches.

Save time by reducing PV re-searches above original depth. Instead use 5% extra time on every move.

STC 10+0.1 th 1 :
LLR: 2.93 (-2.94,2.94) {-0.25,1.25}
Total: 90688 W: 9702 L: 9436 D: 71550 Elo +1.02
Ptnml(0-2): 408, 7252, 29792, 7450, 442
https://tests.stockfishchess.org/tests/view/5f8df807bacb75a4f9a47223

LTC 60+0.6 th 1 :
LLR: 2.97 (-2.94,2.94) {0.25,1.25}
Total: 97856 W: 4602 L: 4303 D: 88951 Elo +1.06
Ptnml(0-2): 53, 3757, 41057, 3960, 101
https://tests.stockfishchess.org/tests/view/5f8ec4872c92c7fe3a8c602d

closes https://github.com/official-stockfish/Stockfish/pull/3192

Bench 3943959
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Vizvezdenec
Date: Sun Oct 18 13:54:28 2020 +0200
Timestamp: 1603022068

Do more reductions for late quiet moves in case of consecutive fail highs.

Idea of this patch can be described as following - in case we have consecutive fail highs and we reach late enough moves at root node probability of remaining quiet moves being able to produce even bigger value than moves that produced previous cutoff (so ones that should be high in move ordering but now they fail to produce beta cutoff because we actually reached high move count) should be quiet small so we can reduce them more.

passed STC
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 53392 W: 5681 L: 5474 D: 42237 Elo +1.35
Ptnml(0-2): 214, 4104, 17894, 4229, 255
https://tests.stockfishchess.org/tests/view/5f88501adcdad978fe8c527e

passed LTC
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 59136 W: 2773 L: 2564 D: 53799 Elo +1.23
Ptnml(0-2): 30, 2117, 25078, 2300, 43
https://tests.stockfishchess.org/tests/view/5f884dbfdcdad978fe8c527a

closes https://github.com/official-stockfish/Stockfish/pull/3184

Bench: 4066972
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: mstembera
Date: Sun Oct 18 13:43:26 2020 +0200
Timestamp: 1603021406

Update default net to nn-eba324f53044.nnue

The new net is based on the previous net 04cf2b4ed1da but with the biases
for the 1st hidden layer tuned SPSA, see the SPSA session on fishtest there:
https://tests.stockfishchess.org/tests/view/5f875213dcdad978fe8c5211

Thanks to @vondele for writing out the net, see discussion in this thread:
https://github.com/mstembera/Stockfish/commit/432da86721647dff1d9426a7cdcfd2dbada8155e

Passed STC:
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 15000 W: 1640 L: 1483 D: 11877 Elo +3.64
Ptnml(0-2): 50, 1183, 4908, 1278, 81
https://tests.stockfishchess.org/tests/view/5f8955e20fea1a44ec4f0a5d

Passed LTC:
LLR: 2.96 (-2.94,2.94) {0.25,1.25}
Total: 81272 W: 3948 L: 3682 D: 73642 Elo +1.14
Ptnml(0-2): 64, 3194, 33856, 3456, 66
https://tests.stockfishchess.org/tests/view/5f89e8efeae8a6e60644d6e7

closes https://github.com/official-stockfish/Stockfish/pull/3187

Bench: 3762411
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Unai Corzo
Date: Wed Oct 14 19:32:12 2020 +0200
Timestamp: 1602696732

Scale factor tweak

Add !pawnsOnBothFlanks heuristic to scale factor.

STC https://tests.stockfishchess.org/tests/view/5f8080575b3847b5d41f9134
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 250960 W: 49779 L: 49168 D: 152013 Elo +0.85
Ptnml(0-2): 4224, 28822, 58802, 29383, 4249

LTC https://tests.stockfishchess.org/tests/view/5f832f498ea73fb8ddf83ddb
LLR: 2.95 (-2.94,2.94) {0.25,1.25}
Total: 88584 W: 11827 L: 11388 D: 65369 Elo +1.72
Ptnml(0-2): 585, 8079, 26578, 8412, 638

closes https://github.com/official-stockfish/Stockfish/pull/3179

bench: 3834252
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: FauziAkram
Date: Wed Oct 14 19:29:22 2020 +0200
Timestamp: 1602696562

RookOnQueenFile Removal

Removing Rook On Queen File looks beneficial, and it might even bring some ELO.
I will try to reintroduce it with a different method later on.

Passed STC:
https://tests.stockfishchess.org/tests/view/5f7cea204389873867eb10cb
LLR: 2.94 (-2.94,2.94) {-1.25,0.25}
Total: 18624 W: 3800 L: 3568 D: 11256 Elo +4.33
Ptnml(0-2): 308, 2131, 4257, 2253, 363

Passed LTC:
https://tests.stockfishchess.org/tests/view/5f7d76a4e936c6892bf50598
LLR: 2.95 (-2.94,2.94) {-0.75,0.25}
Total: 117864 W: 15515 L: 15340 D: 87009 Elo +0.52
Ptnml(0-2): 926, 11127, 34671, 11262, 946

closes https://github.com/official-stockfish/Stockfish/pull/3176

Bench: 3756191
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
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: Wed Oct 14 13:28:21 2020 +0200
Timestamp: 1602674901

Update default net to nn-04cf2b4ed1da.nnue

Further tune the net parameters, now the last but one layer (32x32).
To limit the number of parameters optimized, the network layer was
decomposed using SVD, and the singular values were treated
as parameters and tuned.

Tuning branch: https://github.com/vondele/Stockfish/tree/svdTune
Tuner: https://github.com/vondele/nevergrad4sf

passed STC:
https://tests.stockfishchess.org/tests/view/5f83e82f8ea73fb8ddf83e4e
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 8488 W: 944 L: 795 D: 6749 Elo +6.10
Ptnml(0-2): 39, 609, 2811, 734, 51

passed LTC:
https://tests.stockfishchess.org/tests/view/5f83f4118ea73fb8ddf83e66
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 169016 W: 8043 L: 7589 D: 153384 Elo +0.93
Ptnml(0-2): 133, 6623, 70538, 7085, 129

closes https://github.com/official-stockfish/Stockfish/pull/3181

Bench: 3945198
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: FauziAkram
Date: Mon Oct 5 19:01:46 2020 +0200
Timestamp: 1601917306

Pawn Tuning

Tuning of pawns, for classical evaluation:

Passed STC:
https://tests.stockfishchess.org/tests/view/5f771f0e52560f5fc78559ec
LLR: 2.96 (-2.94,2.94) {-0.25,1.25}
Total: 252696 W: 50321 L: 49692 D: 152683 Elo +0.86
Ptnml(0-2): 4614, 29845, 57049, 29978, 4862

Passed LTC:
https://tests.stockfishchess.org/tests/view/5f77cfef090dcf9aaa16d38b
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 48184 W: 6556 L: 6193 D: 35435 Elo +2.62
Ptnml(0-2): 335, 4516, 14100, 4733, 408

closes https://github.com/official-stockfish/Stockfish/pull/3169

bench: 4016121
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Unai Corzo
Date: Mon Oct 5 18:59:02 2020 +0200
Timestamp: 1601917142

Simplify away futility pruning for captures

Remove futility pruning for captures.

STC https://tests.stockfishchess.org/tests/view/5f749bfed930428c36d34c56
LLR: 2.94 (-2.94,2.94) {-1.25,0.25}
Total: 38064 W: 4011 L: 3929 D: 30124 Elo +0.75
Ptnml(0-2): 192, 3004, 12567, 3068, 201

LTC https://tests.stockfishchess.org/tests/view/5f74d99bf18675b1ce2f7412
LLR: 2.94 (-2.94,2.94) {-0.75,0.25}
Total: 184984 W: 8567 L: 8610 D: 167807 Elo -0.08
Ptnml(0-2): 146, 7593, 77058, 7548, 147

closes https://github.com/official-stockfish/Stockfish/pull/3166

bench: 3890648
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
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 Oct 5 18:56:49 2020 +0200
Timestamp: 1601917009

Schedule threads fairly under valgrind

fixes a rare case that can cause CI to fail when running multithreaded under valgrind.

closes https://github.com/official-stockfish/Stockfish/pull/3165

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
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Stéphane Nicolet
Date: Mon Sep 28 22:42:26 2020 +0200
Timestamp: 1601325746

Include pawns in NNUE scaling

We now include the total pawn count in the scaling factor for the output
of the NNUE evaluation network. This should have the effect of trying to
keep more pawns when SF has the advantage, but exchange them when she
is defending.

Thanks to Alexander Pagel (Lolligerhans) for the idea of using the
value of pawns to ease the comparison with the rest of the material
estimation.

Passed STC:
LLR: 2.93 (-2.94,2.94) {-0.25,1.25}
Total: 15072 W: 1700 L: 1539 D: 11833 Elo +3.71
Ptnml(0-2): 65, 1202, 4845, 1355, 69
https://tests.stockfishchess.org/tests/view/5f7235a63b22d6afa50699b3

Passed LTC:
LLR: 2.93 (-2.94,2.94) {0.25,1.25}
Total: 25880 W: 1270 L: 1124 D: 23486 Elo +1.96
Ptnml(0-2): 23, 980, 10788, 1126, 23
https://tests.stockfishchess.org/tests/view/5f723b483b22d6afa5069a99

closes https://github.com/official-stockfish/Stockfish/pull/3164

Bench: 3776081
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
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: Mon Sep 28 22:34:25 2020 +0200
Timestamp: 1601325265

Tweak reduction formula.

Replace log(i) with log(i + 0.25 * log(i)). This increases especially for low values the reductions. But for bigger values there are nearly no changes.

STC:
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 49640 W: 5505 L: 5289 D: 38846 Elo +1.51
Ptnml(0-2): 270, 4074, 15924, 4274, 278
https://tests.stockfishchess.org/tests/view/5f71f04d3b22d6afa5069478

LTC:
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 43856 W: 2209 L: 2021 D: 39626 Elo +1.49
Ptnml(0-2): 32, 1776, 18128, 1956, 36
https://tests.stockfishchess.org/tests/view/5f7232ee3b22d6afa50699a2

closes https://github.com/official-stockfish/Stockfish/pull/3163

Bench: 3555769
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: SFisGOD
Date: Mon Sep 28 22:29:31 2020 +0200
Timestamp: 1601324971

Update default net to nn-baeb9ef2d183.nnue

Further optimization of Sergio's nn-03744f8d56d8.nnue
This patch is the result of collaboration with Joost VandeVondele.

STC:
LLR: 2.96 (-2.94,2.94) {-0.25,1.25}
Total: 37000 W: 4145 L: 3947 D: 28908 Elo +1.86
Ptnml(0-2): 191, 3016, 11912, 3166, 215
https://tests.stockfishchess.org/tests/view/5f71e7983b22d6afa5069475

LTC:
LLR: 2.96 (-2.94,2.94) {0.25,1.25}
Total: 60224 W: 2992 L: 2769 D: 54463 Elo +1.29
Ptnml(0-2): 48, 2420, 24956, 2637, 51
https://tests.stockfishchess.org/tests/view/5f722bb83b22d6afa506998f

closes https://github.com/official-stockfish/Stockfish/pull/3161

Bench: 3720073
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: FauziAkram
Date: Mon Sep 28 22:26:37 2020 +0200
Timestamp: 1601324797

Tweaking Mobility and Safe Check

Passed STC:
https://tests.stockfishchess.org/tests/view/5f70d86d3b22d6afa50693b9
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 100368 W: 20323 L: 19914 D: 60131 Elo +1.42
Ptnml(0-2): 1927, 11641, 22605, 12118, 1893

Passed LTC:
https://tests.stockfishchess.org/tests/view/5f71bb553b22d6afa5069457
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 77648 W: 10613 L: 10181 D: 56854 Elo +1.93
Ptnml(0-2): 634, 7280, 22594, 7652, 664

closes https://github.com/official-stockfish/Stockfish/pull/3160

Bench: 3861984
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Vizvezdenec
Date: Mon Sep 28 22:22:54 2020 +0200
Timestamp: 1601324574

Adjust null move pruning constants

Idea is that division by fraction of 2 is slightly faster than by other numbers so parameters are adjusted in a way that division in null move pruning depth reduction features dividing by 256 instead of dividing by 213.
Other than this patch is almost non-functional - difference starts to exist by depth 133.

passed STC
https://tests.stockfishchess.org/tests/view/5f70dd943b22d6afa50693c5
LLR: 2.95 (-2.94,2.94) {-0.25,1.25}
Total: 57048 W: 6616 L: 6392 D: 44040 Elo +1.36
Ptnml(0-2): 304, 4583, 18531, 4797, 309

passed LTC
https://tests.stockfishchess.org/tests/view/5f7180db3b22d6afa506941f
LLR: 2.95 (-2.94,2.94) {0.25,1.25}
Total: 45960 W: 2419 L: 2229 D: 41312 Elo +1.44
Ptnml(0-2): 43, 1779, 19137, 1987, 34

closes https://github.com/official-stockfish/Stockfish/pull/3159

bench 3789924
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
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 Sep 28 16:55:40 2020 +0200
Timestamp: 1601304940

Update default net to nn-04a843f8932e.nnue

an optimization of Sergio's nn-03744f8d56d8.nnue tuning the output layer (33 parameters) on game play.

WIP code to make layer parameters tunable is https://github.com/vondele/Stockfish/tree/optionOutput
Optimization itself is using https://github.com/vondele/nevergrad4sf
Writing of the modified net using WIP code based on the learner code https://github.com/vondele/Stockfish/tree/evalWrite

Most parameters in the output layer are changed only little (~5 for int8_t).

passed STC:
https://tests.stockfishchess.org/tests/view/5f716f6b3b22d6afa506941a
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 15488 W: 1859 L: 1689 D: 11940 Elo +3.81
Ptnml(0-2): 79, 1260, 4917, 1388, 100

passed LTC:
https://tests.stockfishchess.org/tests/view/5f71908e3b22d6afa506942e
LLR: 2.93 (-2.94,2.94) {0.25,1.25}
Total: 8728 W: 518 L: 400 D: 7810 Elo +4.70
Ptnml(0-2): 7, 338, 3556, 456, 7

closes https://github.com/official-stockfish/Stockfish/pull/3158

Bench: 3789924
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: noobpwnftw
Date: Mon Sep 28 16:54:35 2020 +0200
Timestamp: 1601304875

Use incremental updates more often

Use incremental updates for accumulators for up to 2 plies.
Do not copy accumulator. About 2% speedup.

Passed STC:
LLR: 2.95 (-2.94,2.94) {-0.25,1.25}
Total: 21752 W: 2583 L: 2403 D: 16766 Elo +2.88
Ptnml(0-2): 128, 1761, 6923, 1931, 133
https://tests.stockfishchess.org/tests/view/5f7150cf3b22d6afa5069412

closes https://github.com/official-stockfish/Stockfish/pull/3157

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
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Stéphane Nicolet
Date: Sun Sep 27 08:24:50 2020 +0200
Timestamp: 1601187890

Tweak nnue scaling to keep more material

Current master uses a constant scale factor of 5/4 = 1.25 for the output
of the NNUE network, for compatibility with search and classical evaluation.
We modify this scale factor to make it dependent on the phase of the game,
going from about 1.5 in the opening to 1.0 for pure pawn endgames.

This helps Stockfish to avoid exchanges of pieces (heavy pieces in particular)
when she has the advantage, keeping more material on the board when attacking.

Passed STC:
LLR: 2.95 (-2.94,2.94) {-0.25,1.25}
Total: 14744 W: 1771 L: 1599 D: 11374 Elo +4.05
Ptnml(0-2): 87, 1184, 4664, 1344, 93
https://tests.stockfishchess.org/tests/view/5f6fb0a63b22d6afa506904f

Passed LTC:
LLR: 2.95 (-2.94,2.94) {0.25,1.25}
Total: 8912 W: 512 L: 393 D: 8007 Elo +4.64
Ptnml(0-2): 7, 344, 3637, 459, 9
https://tests.stockfishchess.org/tests/view/5f6fcf533b22d6afa5069066

closes https://github.com/official-stockfish/Stockfish/pull/3154

Bench: 3943952
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Windows 32
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: SFisGOD
Date: Fri Sep 25 17:44:19 2020 +0200
Timestamp: 1601048659

Switch to NNUE eval probabilistically for OCB

Introduce a small chance of switching to NNUE if PSQ imbalance is large but we have opposite colored bishops and the classical eval is struggling to win.

STC:
LLR: 2.94 (-2.94,2.94) {-0.25,1.25}
Total: 25304 W: 3179 L: 2983 D: 19142 Elo +2.69
Ptnml(0-2): 172, 2171, 7781, 2345, 183
https://tests.stockfishchess.org/tests/view/5f6b14dec7759d4ee307cfe3

LTC:
LLR: 2.94 (-2.94,2.94) {0.25,1.25}
Total: 84680 W: 4846 L: 4556 D: 75278 Elo +1.19
Ptnml(0-2): 89, 3933, 34011, 4213, 94
https://tests.stockfishchess.org/tests/view/5f6b3fb6c7759d4ee307cff9

closes https://github.com/official-stockfish/Stockfish/pull/3146

Bench: 3865413
see source

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