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 Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Linmiao Xu
Date: Fri Sep 22 19:26:16 2023 +0200
Timestamp: 1695403576

Update NNUE architecture to SFNNv8: L1-2560 nn-ac1dbea57aa3.nnue

Creating this net involved:
- a 6-stage training process from scratch. The datasets used in stages 1-5 were fully minimized.
- permuting L1 weights with https://github.com/official-stockfish/nnue-pytorch/pull/254

A strong epoch after each training stage was chosen for the next. The 6 stages were:

```
1. 400 epochs, lambda 1.0, default LR and gamma
UHOx2-wIsRight-multinet-dfrc-n5000 (135G)
nodes5000pv2_UHO.binpack
data_pv-2_diff-100_nodes-5000.binpack
wrongIsRight_nodes5000pv2.binpack
multinet_pv-2_diff-100_nodes-5000.binpack
dfrc_n5000.binpack

2. 800 epochs, end-lambda 0.75, LR 4.375e-4, gamma 0.995, skip 12
LeelaFarseer-T78juntoaugT79marT80dec.binpack (141G)
T60T70wIsRightFarseerT60T74T75T76.binpack
test78-junjulaug2022-16tb7p.no-db.min.binpack
test79-mar2022-16tb7p.no-db.min.binpack
test80-dec2022-16tb7p.no-db.min.binpack

3. 800 epochs, end-lambda 0.725, LR 4.375e-4, gamma 0.995, skip 20
leela93-v1-dfrc99-v2-T78juntosepT80jan-v6dd-T78janfebT79aprT80aprmay.min.binpack
leela93-filt-v1.min.binpack
dfrc99-16tb7p-filt-v2.min.binpack
test78-juntosep2022-16tb7p-filter-v6-dd.min-mar2023.binpack
test80-jan2023-3of3-16tb7p-filter-v6-dd.min-mar2023.binpack
test78-janfeb2022-16tb7p.min.binpack
test79-apr2022-16tb7p.min.binpack
test80-apr2022-16tb7p.min.binpack
test80-may2022-16tb7p.min.binpack

4. 800 epochs, end-lambda 0.7, LR 4.375e-4, gamma 0.995, skip 24
leela96-dfrc99-v2-T78juntosepT79mayT80junsepnovjan-v6dd-T80mar23-v6-T60novdecT77decT78aprmayT79aprT80may23.min.binpack
leela96-filt-v2.min.binpack
dfrc99-16tb7p-filt-v2.min.binpack
test78-juntosep2022-16tb7p-filter-v6-dd.min-mar2023.binpack
test79-may2022-16tb7p.filter-v6-dd.min.binpack
test80-jun2022-16tb7p.filter-v6-dd.min.binpack
test80-sep2022-16tb7p.filter-v6-dd.min.binpack
test80-nov2022-16tb7p.filter-v6-dd.min.binpack
test80-jan2023-3of3-16tb7p-filter-v6-dd.min-mar2023.binpack
test80-mar2023-2tb7p.v6-sk16.min.binpack
test60-novdec2021-16tb7p.min.binpack
test77-dec2021-16tb7p.min.binpack
test78-aprmay2022-16tb7p.min.binpack
test79-apr2022-16tb7p.min.binpack
test80-may2023-2tb7p.min.binpack

5. 960 epochs, end-lambda 0.7, LR 4.375e-4, gamma 0.995, skip 28
Increased max-epoch to 960 near the end of the first 800 epochs
5af11540bbfe dataset: https://github.com/official-stockfish/Stockfish/pull/4635

6. 1000 epochs, end-lambda 0.7, LR 4.375e-4, gamma 0.995, skip 28
Increased max-epoch to 1000 near the end of the first 800 epochs
1ee1aba5ed dataset: https://github.com/official-stockfish/Stockfish/pull/4782
```

L1 weights permuted with:
```bash
python3 serialize.py $nnue $nnue_permuted \
--features=HalfKAv2_hm \
--ft_optimize \
--ft_optimize_data=/data/fishpack32.binpack \
--ft_optimize_count=10000
```

Speed measurements from 100 bench runs at depth 13 with profile-build x86-64-avx2:
```
sf_base = 1329051 +/- 2224 (95%)
sf_test = 1163344 +/- 2992 (95%)
diff = -165706 +/- 4913 (95%)
speedup = -12.46807% +/- 0.370% (95%)
```

Training data can be found at:
https://robotmoon.com/nnue-training-data/

Local elo at 25k nodes per move (vs. L1-2048 nn-1ee1aba5ed4c.nnue)
ep959 : 16.2 +/- 2.3

Failed 10+0.1 STC:
https://tests.stockfishchess.org/tests/view/6501beee2cd016da89abab21
LLR: -2.92 (-2.94,2.94) <0.00,2.00>
Total: 13184 W: 3285 L: 3535 D: 6364 Elo -6.59
Ptnml(0-2): 85, 1662, 3334, 1440, 71

Failed 180+1.8 VLTC:
https://tests.stockfishchess.org/tests/view/6505cf9a72620bc881ea908e
LLR: -2.94 (-2.94,2.94) <0.00,2.00>
Total: 64248 W: 16224 L: 16374 D: 31650 Elo -0.81
Ptnml(0-2): 26, 6788, 18640, 6650, 20

Passed 60+0.6 th 8 VLTC SMP (STC bounds):
https://tests.stockfishchess.org/tests/view/65084a4618698b74c2e541dc
LLR: 2.95 (-2.94,2.94) <0.00,2.00>
Total: 90630 W: 23372 L: 23033 D: 44225 Elo +1.30
Ptnml(0-2): 13, 8490, 27968, 8833, 11

Passed 60+0.6 th 8 VLTC SMP:
https://tests.stockfishchess.org/tests/view/6501d45d2cd016da89abacdb
LLR: 2.95 (-2.94,2.94) <0.50,2.50>
Total: 137804 W: 35764 L: 35276 D: 66764 Elo +1.23
Ptnml(0-2): 31, 13006, 42326, 13522, 17

closes https://github.com/official-stockfish/Stockfish/pull/4795

bench 1246812
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Stefan Geschwentner
Date: Fri Sep 22 19:25:57 2023 +0200
Timestamp: 1695403557

Remove VALUE_KNOWN_WIN.

After removing classic evaluation VALUE_KNOWN_WIN is not anymore returned explicit evaluation. So remove and replace it with VALUE_TB_WIN_IN_MAX_PLY.

Measurement on my big bench (bench 16 1 16 pos1000.fen) verifies that at least with current net the calculated evaluation lies always in the open interval (-VALUE_KNOWN_WIN, VALUE_KNOWN_WIN).
So i consider this a non-functional change. But to be safe i tested this also at LTC as requested by Stephane Nicolet.

STC:
https://tests.stockfishchess.org/tests/view/64f9db40eaf01be8259a6ed5
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 455296 W: 115981 L: 116217 D: 223098 Elo -0.18
Ptnml(0-2): 1415, 50835, 123420, 50527, 1451

LTC:
https://tests.stockfishchess.org/tests/view/650bfd867ca0d3f7bbf25feb
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 35826 W: 9170 L: 8973 D: 17683 Elo +1.91
Ptnml(0-2): 12, 3523, 10645, 3722, 11

closes https://github.com/official-stockfish/Stockfish/pull/4792

Bench: 1603079
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: mstembera
Date: Fri Sep 22 19:15:34 2023 +0200
Timestamp: 1695402934

Reduce SIMD register count from 32 to 16

in the case of avx512 and vnni512 archs.

Up to 17% speedup, depending on the compiler, e.g.

```
AMD pro 7840u (zen4 phoenix apu 4nm)
bash bench_parallel.sh ./stockfish_avx512_gcc13 ./stockfish_avx512_pr_gcc13 20 10
sf_base = 1077737 +/- 8446 (95%)
sf_test = 1264268 +/- 8543 (95%)
diff = 186531 +/- 4280 (95%)
speedup = 17.308% +/- 0.397% (95%)
```

Prior to this patch, it appears gcc spills registers.

closes https://github.com/official-stockfish/Stockfish/pull/4796

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: cj5716
Date: Fri Sep 22 19:14:29 2023 +0200
Timestamp: 1695402869

Make casting styles consistent

Make casting styles consistent with the rest of the code.

closes https://github.com/official-stockfish/Stockfish/pull/4793

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Sebastian Buchwald
Date: Fri Sep 22 19:12:53 2023 +0200
Timestamp: 1695402773

Let CI check C++ includes

The commit adds a CI workflow that uses the included-what-you-use (IWYU)
tool to check for missing or superfluous includes in .cpp files and
their corresponding .h files. This means that some .h files (especially
in the nnue folder) are not checked yet.

The CI setup looks like this:
- We build IWYU from source to include some yet unreleased fixes.
This IWYU version targets LLVM 17. Thus, we get the latest release
candidate of LLVM 17 from LLVM's nightly packages.
- The Makefile now has an analyze target that just build the object
files (without linking)
- The CI uses the analyze target with the IWYU tool as compiler to
analyze the compiled .cpp file and its corresponding .h file.
- If IWYU suggests a change the build fails (-Xiwyu --error).
- To avoid false positives we use LLVM's libc++ as standard library
- We have a custom mappings file that adds some mappings that are
missing in IWYU's default mappings

We also had to add one IWYU pragma to prevent a false positive in
movegen.h.

https://github.com/official-stockfish/Stockfish/pull/4783

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Stéphane Nicolet
Date: Fri Sep 22 19:09:20 2023 +0200
Timestamp: 1695402560

Export makefile ARCH in binary

Example of the `./stockfish compiler` command:

Compiled by : g++ (GNUC) 10.3.0 on Apple
Compilation architecture : x86-64-bmi2
Compilation settings : 64bit BMI2 AVX2 SSE41 SSSE3 SSE2 POPCNT
Compiler __VERSION__ macro : 10.3.0

closes https://github.com/official-stockfish/Stockfish/pull/4789

no functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Joost VandeVondele
Date: Fri Sep 22 19:06:37 2023 +0200
Timestamp: 1695402397

Enable a default native ARCH

uses a posix compatible script to find the native arch.
(based on ppigazzini's https://github.com/ppigazzini/stockfish-downloader )
use that native arch by default, no changes if ARCH is specified explicitly.

SF can now be compiled in an optimal way simply using

make -j profile-build

closes https://github.com/official-stockfish/Stockfish/pull/4777

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: mstembera
Date: Fri Sep 22 19:03:47 2023 +0200
Timestamp: 1695402227

Sparse impl of affine_transform_non_ssse3()

deal with the general case

About a 8.6% speedup (for general arch)

Results for 200 tests for each version:

Base Test Diff
Mean 141741 153998 -12257
StDev 2990 3042 3742

p-value: 0.999
speedup: 0.086

closes https://github.com/official-stockfish/Stockfish/pull/4786

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: peregrineshahin
Date: Fri Sep 22 19:02:18 2023 +0200
Timestamp: 1695402138

Reorder some lines

Now that qsearch has its own repetition detection we can flip the order of lines and remove the guard of depth < 0 which is not needed after reordering (i.e. it was there to prevent checking repetition again at depth ==0).

Passed STC:
https://tests.stockfishchess.org/tests/view/6502ecbb2cd016da89abc3fb
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 69536 W: 17668 L: 17490 D: 34378 Elo +0.89
Ptnml(0-2): 190, 7652, 18929, 7784, 213

Passed LTC:
https://tests.stockfishchess.org/tests/view/6505ce9072620bc881ea9086
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 52116 W: 13294 L: 13113 D: 25709 Elo +1.21
Ptnml(0-2): 26, 5176, 15471, 5361, 24

closes https://github.com/official-stockfish/Stockfish/pull/4791

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Stéphane Nicolet
Date: Mon Sep 11 23:19:06 2023 +0200
Timestamp: 1694467146

Reformat some comments

Also include the bench to make Continuation Integration happy on Github.

Bench: 1603079
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Sebastian Buchwald
Date: Mon Sep 11 22:46:01 2023 +0200
Timestamp: 1694465161

Cleanup code after dropping ICC support in favor of ICX

The commit removes all uses of ICC's __INTEL_COMPILER macro and other
references to ICC. It also adds ICX info to the compiler command and
fixes two typos in Makefile's help output.

closes https://github.com/official-stockfish/Stockfish/pull/4769

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Linmiao Xu
Date: Mon Sep 11 22:37:39 2023 +0200
Timestamp: 1694464659

Update default net to nn-1ee1aba5ed4c.nnue

Created by retraining the master net on a dataset composed by:
- adding Leela data from T60 jul-dec 2020, T77 nov 2021, T80 jun-jul 2023
- deduplicating and unminimizing parts of the dataset before interleaving

Trained initially with max epoch 800, then increased near the end of training
twice. First to 960, then 1200. After training, post-processing involved:
- greedy permuting L1 weights with https://github.com/official-stockfish/Stockfish/pull/4620
- greedy 2- and 3- cycle permuting with https://github.com/official-stockfish/Stockfish/pull/4640

python3 easy_train.py \
--experiment-name 2048-retrain-S6-sk28 \
--training-dataset /data/S6.binpack \
--early-fen-skipping 28 \
--start-from-engine-test-net True \
--max_epoch 1200 \
--lr 4.375e-4 \
--gamma 0.995 \
--start-lambda 1.0 \
--end-lambda 0.7 \
--tui False \
--seed $RANDOM \
--gpus 0

In the list of datasets below, periods in the filename represent the sequence of
steps applied to arrive at the particular binpack. For example:

test77-dec2021-16tb7p.filter-v6-dd.min-mar2023.unminimized.binpack
1. test77 dec2021 data rescored with 16 TB of syzygy tablebases during data conversion
2. filtered with csv_filter_v6_dd.py - v6 filtering and deduplication in one step
3. minimized with the original mar2023 implementation of `minimize_binpack` in
the tools branch
4. unminimized by removing all positions with score == 32002 (`VALUE_NONE`)

Binpacks were:
- filtered with: https://github.com/linrock/nnue-data
- unminimized with: https://github.com/linrock/Stockfish/tree/tools-unminify
- deduplicated with: https://github.com/linrock/Stockfish/tree/tools-dd

DATASETS=(
leela96-filt-v2.min.unminimized.binpack
dfrc99-16tb7p-eval-filt-v2.min.unminimized.binpack

# most of the 0dd1cebea57 v6-dd dataset (without test80-jul2022)
# https://github.com/official-stockfish/Stockfish/pull/4606
test60-novdec2021-12tb7p.filter-v6-dd.min-mar2023.unminimized.binpack
test77-dec2021-16tb7p.filter-v6-dd.min-mar2023.unminimized.binpack
test78-jantomay2022-16tb7p.filter-v6-dd.min-mar2023.unminimized.binpack
test78-juntosep2022-16tb7p.filter-v6-dd.min-mar2023.unminimized.binpack
test79-apr2022-16tb7p.filter-v6-dd.min-mar2023.unminimized.binpack
test79-may2022-16tb7p.filter-v6-dd.min-mar2023.unminimized.binpack
test80-jun2022-16tb7p.filter-v6-dd.min-mar2023.unminimized.binpack
test80-aug2022-16tb7p.filter-v6-dd.min-mar2023.unminimized.binpack
test80-sep2022-16tb7p.filter-v6-dd.min-mar2023.unminimized.binpack
test80-oct2022-16tb7p.filter-v6-dd.min.binpack
test80-nov2022-16tb7p.filter-v6-dd.min.binpack
test80-jan2023-3of3-16tb7p.filter-v6-dd.min-mar2023.unminimized.binpack
test80-feb2023-16tb7p.filter-v6-dd.min-mar2023.unminimized.binpack

# older Leela data, recently converted
test60-octnovdec2020-2tb7p.min.unminimized.binpack
test60-julaugsep2020-2tb7p.min.binpack
test77-nov2021-2tb7p.min.dd.binpack

# newer Leela data
test80-mar2023-2tb7p.min.unminimized.binpack
test80-apr2023-2tb7p.filter-v6-sk16.min.unminimized.binpack
test80-may2023-2tb7p.min.dd.binpack
test80-jun2023-2tb7p.min.binpack
test80-jul2023-2tb7p.binpack
)
python3 interleave_binpacks.py ${DATASETS[@]} /data/S6.binpack

Training data can be found at:
https://robotmoon.com/nnue-training-data/

Local elo at 25k nodes per move:
nn-epoch1059 : 2.7 +/- 1.6

Passed STC:
https://tests.stockfishchess.org/tests/view/64fc8d705dab775b5359db42
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 168352 W: 43216 L: 42704 D: 82432 Elo +1.06
Ptnml(0-2): 599, 19672, 43134, 20160, 611

Passed LTC:
https://tests.stockfishchess.org/tests/view/64fd44a75dab775b5359f065
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 154194 W: 39436 L: 38881 D: 75877 Elo +1.25
Ptnml(0-2): 78, 16577, 43238, 17120, 84

closes https://github.com/official-stockfish/Stockfish/pull/4782

Bench: 1603079
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Michael Chaly
Date: Mon Sep 11 22:36:26 2023 +0200
Timestamp: 1694464586

Do more futility pruning in qsearch

This patch introduces a third futility pruning heuristic in qsearch. The idea is
that the static exchange evaluation is much worse than the difference between
futility base and alpha. Thus we can assume that the probability of the move
being good enough to beat alpha is low so it can be pruned.

Passed STC:
https://tests.stockfishchess.org/tests/view/64fc982a5dab775b5359dc83
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 36576 W: 9484 L: 9170 D: 17922 Elo +2.98
Ptnml(0-2): 121, 4119, 9495, 4431, 122

Passed LTC:
https://tests.stockfishchess.org/tests/view/64fcc7935dab775b5359e1a9
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 135408 W: 34556 L: 34041 D: 66811 Elo +1.32
Ptnml(0-2): 56, 14462, 38165, 14953, 68

closes https://github.com/official-stockfish/Stockfish/pull/4781

Bench: 1330793
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: cj5716
Date: Mon Sep 11 22:30:57 2023 +0200
Timestamp: 1694464257

Simplify cutnode depth condition

With this patch, the depth condition for the cutnodes reduction is loosened from
tte->depth() >= depth + 3 to just tte->depth() >= depth.

Passed STC:
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 101152 W: 25830 L: 25682 D: 49640 Elo +0.51
Ptnml(0-2): 312, 11788, 26258, 11876, 342
https://tests.stockfishchess.org/tests/view/64fd15635dab775b5359eaa6

Passed LTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 82542 W: 20980 L: 20824 D: 40738 Elo +0.66
Ptnml(0-2): 42, 8795, 23440, 8953, 41
https://tests.stockfishchess.org/tests/view/64fda3545dab775b5359fbf1

closes https://github.com/official-stockfish/Stockfish/pull/4780

Bench: 1479029
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Sebastian Buchwald
Date: Mon Sep 11 22:15:22 2023 +0200
Timestamp: 1694463322

Cleanup git checkout actions

We now fetch only the current commit for jobs that don't need the git
history. For the Prerelease job, we don't checkout the code at all.

closes https://github.com/official-stockfish/Stockfish/pull/4779

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Tomasz Sobczyk
Date: Mon Sep 11 22:11:30 2023 +0200
Timestamp: 1694463090

Prevent usage of AVX-512 for the last layer.

Add more static checks regarding the SIMD width match.

STC: https://tests.stockfishchess.org/tests/view/64f5c568a9bc5a78c669e70e
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 125216 W: 31756 L: 31636 D: 61824 Elo +0.33
Ptnml(0-2): 327, 13993, 33848, 14113, 327

Fixes a bug introduced in 2f2f45f, where with AVX-512 the weights and input to
the last layer were being read out of bounds. Now AVX-512 is only used for the
layers it can be used for. Additional static assertions have been added to
prevent more errors like this in the future.

closes https://github.com/official-stockfish/Stockfish/pull/4773

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Sebastian Buchwald
Date: Mon Sep 11 22:07:55 2023 +0200
Timestamp: 1694462875

Avoid "using namespace std"

This is a cleanup PR that prepares the automatic checking of missing or
superfluous #include directives via the include-what-you-use (IWYU) tool
on the CI. Unfortunately, IWYU proposes additional includes for
"namespace std" although we don't need them.

To avoid the problem, the commit removes all "using namespace std"
statements from the code and directly uses the std:: prefix instead.
Alternatively, we could add specific usings (e.g. "using std::string")
foreach used type. Also, a mix of both approaches would be possible.
I decided for the prefix approach because most of the files were already
using the std:: prefixes despite the "using namespace std".

closes https://github.com/official-stockfish/Stockfish/pull/4772

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Stéphane Nicolet
Date: Sun Sep 3 09:28:16 2023 +0200
Timestamp: 1693726096

Introduce simple_eval() for lazy evaluations

This patch implements the pure materialistic evaluation called simple_eval()
to gain a speed-up during Stockfish search.

We use the so-called lazy evaluation trick: replace the accurate but slow
NNUE network evaluation by the super-fast simple_eval() if the position
seems to be already won (high material advantage). To guard against some
of the most obvious blunders introduced by this idea, this patch uses the
following features which will raise the lazy evaluation threshold in some
situations:

- avoid lazy evals on shuffling branches in the search tree
- avoid lazy evals if the position at root already has a material imbalance
- avoid lazy evals if the search value at root is already winning/losing.

Moreover, we add a small random noise to the simple_eval() term. This idea
(stochastic mobility in the minimax tree) was worth about 200 Elo in the pure
simple_eval() player on Lichess.

Overall, the current implementation in this patch evaluates about 2% of the
leaves in the search tree lazily.

--------------------------------------------

STC:
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 60352 W: 15585 L: 15234 D: 29533 Elo +2.02
Ptnml(0-2): 216, 6906, 15578, 7263, 213
https://tests.stockfishchess.org/tests/view/64f1d9bcbd9967ffae366209

LTC:
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 35106 W: 8990 L: 8678 D: 17438 Elo +3.09
Ptnml(0-2): 14, 3668, 9887, 3960, 24
https://tests.stockfishchess.org/tests/view/64f25204f5b0c54e3f04c0e7

verification run at VLTC:
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 74362 W: 19088 L: 18716 D: 36558 Elo +1.74
Ptnml(0-2): 6, 7226, 22348, 7592, 9
https://tests.stockfishchess.org/tests/view/64f2ecdbf5b0c54e3f04d3ae

All three tests above were run with adjudication off, we also verified that
there was no regression on matetracker (thanks Disservin!).

----------------------------------------------

closes https://github.com/official-stockfish/Stockfish/pull/4771

Bench: 1393714
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: FauziAkram
Date: Sun Sep 3 09:10:27 2023 +0200
Timestamp: 1693725027

Rename one variable

To enhance code clarity and prevent potential confusion with the
'r' variable assigned to reduction later in the code, this pull
request renames it to 'reductionScale' when we use the same name
in the reduction() function.

Using distinct variable names for separate functions improves code
readability and maintainability.

closes https://github.com/official-stockfish/Stockfish/pull/4765

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: pb00067
Date: Sun Sep 3 08:57:43 2023 +0200
Timestamp: 1693724263

Simplify slider_blocker calculation

Now that classical evaluation was removed, we can adapt this method
to the needs of set_check_info.

STC:
2.95 (-2.94,2.94) <-1.75,0.25>
Total: 298176 W: 75802 L: 75868 D: 146506 Elo -0.08
Ptnml(0-2): 908, 33608, 80192, 33402, 978
https://tests.stockfishchess.org/tests/view/64e70b899009777747557b43

closes https://github.com/official-stockfish/Stockfish/pull/4753

no functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Disservin
Date: Sun Sep 3 08:40:08 2023 +0200
Timestamp: 1693723208

Simplify README

The UCI protocol is rather technical and has little value in our README. Instead
it should be explained in our wiki. "Contributing" is moved above "Compiling
Stockfish" to make it more prominent.

Also move the CONTRIBUTING.md into the root directory and include it in the
distributed artifacts/releases.

closes https://github.com/official-stockfish/Stockfish/pull/4766

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Disservin
Date: Sun Sep 3 08:24:51 2023 +0200
Timestamp: 1693722291

Cleanup includes

Reorder a few includes, include "position.h" where it was previously missing
and apply include-what-you-use suggestions. Also make the order of the includes
consistent, in the following way:

1. Related header (for .cpp files)
2. A blank line
3. C/C++ headers
4. A blank line
5. All other header files

closes https://github.com/official-stockfish/Stockfish/pull/4763
fixes https://github.com/official-stockfish/Stockfish/issues/4707

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: ttruscott
Date: Sun Sep 3 08:07:59 2023 +0200
Timestamp: 1693721279

Omit two unneeded tests

These redundant tests were intended as a speed-up, but they do not seem
to provide any speed anymore.

STC: https://tests.stockfishchess.org/tests/view/64e9079c85e3e95030fd8259
LLR: 2.96 (-2.94,2.94) <-1.75,0.25>
Total: 134688 W: 34338 L: 34226 D: 66124 Elo +0.29
Ptnml(0-2): 426, 15122, 36124, 15258, 414

closes https://github.com/official-stockfish/Stockfish/pull/4767

No functional change
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Stéphane Nicolet
Date: Thu Aug 24 08:11:17 2023 +0200
Timestamp: 1692857477

Play turbulent when defending, simpler when attacking

This patch decays a little the evaluation (up to a few percent) for
positions which have a large complexity measure (material imbalance,
positional compensations, etc).

This may have nice consequences on the playing style, as it modifies
the search differently for attack and defense, both effects being
desirable:

- to see the effect on positions when Stockfish is defending, let us
suppose for instance that the side to move is Stockfish and the nnue
evaluation on the principal variation is -100 : this patch will decay
positions with an evaluation of -103 (say) to the same level, provided
they have huge material imbalance or huge positional compensation.
In other words, chaotic positions with an evaluation of -103 are now
comparable in our search tree to stable positions with an evaluation
of -100, and chaotic positions with an evaluation of -102 are now
preferred to stable positions with an evaluation of -100.

- the effect on positions when Stockfish is attacking is the opposite.
Let us suppose for instance that the side to move is Stockfish and the
nnue evaluation on the principal variation is +100 : this patch will
decay the evaluation to +97 if the positions on the principal variation
have huge material imbalance or huge positional compensation. In other
words, stable positions with an evaluation of +97 are now comparable
in our search tree to chaotic positions with an evaluation of +100,
and stable positions with an evaluation of +98 are now preferred to
chaotic positions with an evaluation of +100.

So the effect of this small change of evaluation on the playing style
is that Stockfish should now play a little bit more turbulent when
defending, and choose slightly simpler lines when attacking.

passed STC:
LLR: 2.93 (-2.94,2.94) <0.00,2.00>
Total: 268448 W: 68713 L: 68055 D: 131680 Elo +0.85
Ptnml(0-2): 856, 31514, 68943, 31938, 973
https://tests.stockfishchess.org/tests/view/64e252bb99700912526653ed

passed LTC:
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 141060 W: 36066 L: 35537 D: 69457 Elo +1.30
Ptnml(0-2): 71, 15179, 39522, 15666, 92
https://tests.stockfishchess.org/tests/view/64e4447a9009777747553725

closes https://github.com/official-stockfish/Stockfish/pull/4762

Bench: 1426295
see source
Windows x64 for Haswell CPUs
Windows x64 for modern computers + AVX2
Windows x64 for modern computers
Windows x64 + SSSE3
Windows x64
Linux x64 for Haswell CPUs
Linux x64 for modern computers + AVX2
Linux x64 for modern computers
Linux x64 + SSSE3
Linux x64
Author: Shahin M. Shahin
Date: Tue Aug 22 11:32:51 2023 +0200
Timestamp: 1692696771

Reduce repetitions branches

Increase reduction on retrying a move we just retreated that falls in a repetition:
if current move can be the same move from previous previous turn then we retreated
that move on the previous turn, this patch increases reduction if retrying that move
results in a repetition.

How to continue from there? Maybe we some variants of this idea could bring Elo too
(only testing the destination square, or triangulations, etc.)

Passed STC:
https://tests.stockfishchess.org/tests/view/64e1aede883cbb7cbd9ad976
LLR: 2.94 (-2.94,2.94) <0.00,2.00>
Total: 424000 W: 108675 L: 107809 D: 207516 Elo +0.71
Ptnml(0-2): 1296, 47350, 113896, 48108, 1350

Passed LTC:
https://tests.stockfishchess.org/tests/view/64e32d629970091252666872
LLR: 2.94 (-2.94,2.94) <0.50,2.50>
Total: 89682 W: 22976 L: 22569 D: 44137 Elo +1.58
Ptnml(0-2): 39, 8843, 26675, 9240, 44

closes https://github.com/official-stockfish/Stockfish/pull/4757

bench: 1574347
see source

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