Sturddle 2.6 - new version chess engine

Sturddle 2 is a fork of Sturddle Chess Engine (UCI) and neural network.

Author: Cristian (Cristivlas)  Rating Chess Engines Diary CEDR=3325

Building the Engine
The executable bundles binary images that support AVX512, AVX2, and generic SSE2.

Clang is recommended, the GNU C++ compiler may work but it is not supported.
If built with the `NATIVE_UCI` flag, invoke `main.py` to run the UCI engine.
Without the `NATIVE_UCI` flag, run `sturddle.py` instead.
## Training the Neural Net
I have trained the neural net on a large dataset that I generated and curated over a couple of years.

Sturddle 2.6 what's new?

Added SPSA tooling and dashboard (LAN distributed tuner -- experimental)

Fixed aspiration window reset bug that could cause blunders

Fixed bug in uci_native.cpp related to 50-move rule

Streamlined the NN architecture, increased capacity, retrained

ELO improvement over 2.5.0: TC=720+8: 35.88 ±7.94, TC=120+2: 40.5 ± 8.4

Added pytorch version of trainer, revisited existing TensorFlow trainer

Build script improvements, add make-native, NATIVE_BUILD for creating Python-less binaries (not for release, SPSA use only)

Support the go searchmoves UCI command

Sturddle 2.4 vs other engines:

Quirky 2.0	12.5/22	+3	22 Games
Zangdar 4.04.01	6.5/22	-9	22 Games
Reckless 0.8.0	2.5/22	-17	22 Games
Maelstrom 3.3.0	10.5/21	+0	21 Games
Halogen 15.0.0	2/20	-16	20 Games
Claw 2.0-M	2.5/16	-11	16 Games
Revolution 1.0 2708225	1/16	-14	16 Games
Benbot 1.4.4	14/14	+14	14 Games
Critter 1.6a	9/14	+4	14 Games
Invictus r391 JA	8.5/14	+3	14 Games
Cataphract 1.1	4.5/10	-1	10 Games
Pawnocchio 1.8.1	1/10	-8	10 Games
Potential 3.0.0	7.5/9	+6	9 Games
Laser 1.8 beta JA	4/8	+0	8 Games
DarkZoryn 2.0	2/8	-4	8 Games
Stockfish dev-20250902	1.5/8	-5	8 Games
CorChess 20250824	1.5/8	-5	8 Games
Spirit 300825	1.5/8	-5	8 Games
OmegaCor 270825	1.5/8	-5	8 Games
SF SE-240825	1/8	-6	8 Games
Caissa 1.23	1/8	-6	8 Games

Sturddle 2.6 download