akimbo v1.0.0

This (probably) marks the final release where akimbo's NNUE is wholly original, I have spent (wasted?) hundreds of hours of compute generating training data on 6 threads, and really cannot be bothered to do any more of it, so future releases will likely use external data. I have thus incremented the major version number to indicate this, as well as the fact that akimbo now contains all of the biggest functional features (SMP, DFRC, etc).

Main Features

• NNUE Speedups
• A few small search improvements
• Replaced oldest data with new data
• New network, trained on 1.5bn positions with arch (768x4hm -> 1024)x2 -> 1
• Full Changelog: v0.8.0...v1.0.0

Self-Play against v0.8.0

Couldn't be bothered to run a full progtest, it should hopefully scale better due to the larger network.

Elo   | 34.86 +- 16.92 (95%)
Conf  | 40.0+0.40s Threads=1 Hash=128MB
Games | N: 350 W: 56 L: 21 D: 273
Penta | [0, 15, 113, 44, 3]
https://chess.swehosting.se/test/5914/

Selecting a Binary

If possible, choose the avx2 version.

akimbo v0.8.0

Main Features

• Lazy SMP Bugfix
• A number of search improvements.
• New network, trained on 1.5 billion positions with arch (768->768)x2->1.
• Full Changelog: v0.7.0...v0.8.0

Self-Play against v0.7.0

ELO   | 73.01 +- 9.06 (95%)
CONF  | 60.0+0.60s Threads=1 Hash=128MB
GAMES | N: 1748 W: 464 L: 102 D: 1182
https://chess.swehosting.se/test/5233/

Selecting a Binary

If possible, choose the avx2 version.

akimbo v0.7.0

Main Features

• Lazy SMP
• DFRC Support is back
• A number of search improvements (most notably continuation history)
• New network, giuseppe, trained on 1 billion positions with arch 768->512x2->8.

Self-Play against v0.6.0

ELO   | 96.38 +- 9.21 (95%)
CONF  | 60.0+0.60s Threads=1 Hash=128MB
GAMES | N: 2000 W: 654 L: 113 D: 1233
https://chess.swehosting.se/test/4442/

Selecting a Binary

If possible, choose the avx2 version.

akimbo v0.6.0

This release replaces HCE evaluation with a 768 -> 256x2 -> 1 NNUE, codenamed bob, as well as adding a few small search gainers.

The NNUE data is self-generated, building on my HCE data, using my own trainer written from scratch: bullet.

Lines of Code

SLOC: 898
TLOC: 1124

Self-Play Against v0.5.0

ELO   | 387.57 +- 19.94 (95%)
CONF  | 60.0+0.60s Threads=1 Hash=128MB
GAMES | N: 2000 W: 1648 L: 36 D: 316
https://chess.swehosting.se/test/3906/

Selecting a Binary

With the addition of NNUE, there is now a very significant difference between the v1 and v2 binaries vs the v3 and v4 binaries, therefore if you have a CPU that supports v3 or above, I highly recommend using the appropriate binary.

akimbo v0.5.0

This release replaces PSTs with a full Hand-Crafted Evaluation.

The new HCE is trained on wholly original data, generated starting from material values and iterating datagen/tuning until
reaching high enough quality.

Lines of Code

SLOC: 940
TLOC: 1174

Self-Play Against v0.4.0

ELO   | 351.95 +- 20.17 (95%)
CONF  | 60.0+0.60s Threads=1 Hash=128MB
GAMES | N: 2000 W: 1628 L: 94 D: 278
https://chess.swehosting.se/test/3277/

New HCE

• King Relative PSTs
• Passed, Isolated, Blocked Pawns
• Mobility
• Rooks on (Semi-)Open Files

akimbo v0.4.1 - Final PST-Only Version

This serves as the final release where akimbo is PST-only.

Lines of Code

SLOC: 948
TLOC: 1166

Self-play

ELO   | 150.93 +- 11.27 (95%)
CONF  | 60.0+0.60s Threads=1 Hash=128MB
GAMES | N: 2000 W: 947 L: 129 D: 924
https://chess.swehosting.se/test/2987/

VS PeSTO

Relevant comparison to the strongest PST-only engine, PeSTO

Score of akimbo-0.4.1 vs PeSTO-BMI2: 153 - 262 - 85  [0.391] 500
...      akimbo-0.4.1 playing White: 65 - 135 - 50  [0.360] 250
...      akimbo-0.4.1 playing Black: 88 - 127 - 35  [0.422] 250
...      White vs Black: 192 - 223 - 85  [0.469] 500
Elo difference: -77.0 +/- 28.3, LOS: 0.0 %, DrawRatio: 17.0 %

akimbo v0.4.0

EDIT: Prefer the akimbo-x86_64-win-v1.exe binary for older CPUs, the other one was miscompiled.

akimbo became a member of this OpenBench Instance recently, thanks to all involved.

Lines of Code

SLOC: 852     (not counting blank lines and comments)
TLOC: 1039    (counting the above)

Changelog

• Added History Gravity
• Added Late Move Pruning
• Added Aspiration Windows
• Improving in RFP
• Reduce Passed Pawns Less
• Various Tweaks

Self-Play ELO

ELO   | 150.10 +- 12.36 (95%)
CONF  | 60.0+0.60s Threads=1 Hash=128MB
GAMES | N: 2000 W: 1019 L: 205 D: 776
https://chess.swehosting.se/test/2280/

Binaries

Follows the microarchitecture levels:

• v1 is for compatibility with really old architectures
• v2 is popcnt, sse, etc
• v3 is for CPUs that are Haswell/Excavator or newer
• v4 is for the most modern CPUs that support avx512

Please raise an issue if any of the binaries do not work as intended.

Full Changelog: https://github.com/JacquesRW/akimbo/commits/v0.4.0

akimbo v0.3.0

FRC support is back!

Lines of Code

SLOC: 891     (not counting blank lines and comments)
TLOC: 1050    (counting the above)

Changelog

• Switched to Copy/Make
• Fixed a Repetition Detection bug
• Added back FRC support, now extended to DFRC
• Added Razoring
• Added Internal Iterative Reductions (IIR)
• Added Ageing to Hash Table Entries

Self-Play ELO

Time Control: 60s+0.6s
Score of akimbo-0.3.0 vs akimbo-0.2.0: 217 - 80 - 203  [0.637] 500
...      akimbo-0.3.0 playing White: 122 - 31 - 97  [0.682] 250
...      akimbo-0.3.0 playing Black: 95 - 49 - 106  [0.592] 250
...      White vs Black: 171 - 126 - 203  [0.545] 500
Elo difference: 97.7 +/- 23.7, LOS: 100.0 %, DrawRatio: 40.6 %

Binaries

Follows the microarchitecture levels:

• v1 is for compatibility with really old architectures
• v2 is popcnt, sse, etc
• v3 is for CPUs that are Haswell/Excavator or newer

akimbo v0.2.0

Committing to making akimbo tiny:

SLOC: 866
TLOC: 1000

Gain over 0.1.1:

Time Control: 40/60+0.6
Score of dev vs akimbo 0.1.1: 251 - 76 - 273  [0.646] 600
...      dev playing White: 147 - 28 - 125  [0.698] 300
...      dev playing Black: 104 - 48 - 148  [0.593] 300
...      White vs Black: 195 - 132 - 273  [0.552] 600
Elo difference: 104.4 +/- 20.6, LOS: 100.0 %, DrawRatio: 45.5 %

Changelog

• Removed FRC support (for now?).
• Added history heuristic
• Tuned nmp and lmr
• Simplified a lot of code

Major changes:

Date: 02/04
Change: Fixed depth lmr -> Variable depth lmr + history table

Score of dev vs akimbo 0.1.1: 352 - 240 - 408  [0.556] 1000
...      dev playing White: 201 - 97 - 202  [0.604] 500
...      dev playing Black: 151 - 143 - 206  [0.508] 500
...      White vs Black: 344 - 248 - 408  [0.548] 1000
Elo difference: 39.1 +/- 16.6, LOS: 100.0 %, DrawRatio: 40.8 %

Date: 04/24
New: History bonus depth -> depth^2
Score of dev vs old: 316 - 243 - 441  [0.536] 1000
...      dev playing White: 182 - 100 - 218  [0.582] 500
...      dev playing Black: 134 - 143 - 223  [0.491] 500
...      White vs Black: 325 - 234 - 441  [0.545] 1000
Elo difference: 25.4 +/- 16.1, LOS: 99.9 %, DrawRatio: 44.1 %

Date: 05/24
New: Null move pruning reduction 3 -> 2 + depth / 3
Score of dev vs old: 351 - 210 - 439  [0.571] 1000
...      dev playing White: 193 - 82 - 225  [0.611] 500
...      dev playing Black: 158 - 128 - 214  [0.530] 500
...      White vs Black: 321 - 240 - 439  [0.540] 1000
Elo difference: 49.3 +/- 16.2, LOS: 100.0 %, DrawRatio: 43.9 %

akimbo v0.1.1 bugfix

Fixes a depth-related issue when forced stalemates are found.