Triumviratus 4.2 - Own Trained Net

Triumviratus 4.2 — first own-lineage network

The first own-network build of Triumviratus. It evaluates with our own rubicon NNUE, trained from scratch on T80 data — no Stockfish network is shipped. The classical search is unchanged from 4.1; this release is about the network.

What's in this release

Two builds (pick one for your CPU). Each archive contains the engine + the network + a short README.

Archive	CPU requirement
Triumviratus_4.2_avx512.zip	AVX-512 + BMI2 — Intel Ice Lake+/Skylake-X, AMD Zen 4+
Triumviratus_4.2_avx2.zip	AVX2 + BMI2 — Intel Haswell 2013+, AMD Zen+

BMI2 (PEXT) is required. If the AVX-512 build won't start, use the AVX2 one.

Setup

1. Unzip.
2. Keep nn-rubicon-v1.nnue in the same folder as the executable (it's already in the archive).
3. Add the .exe to your UCI GUI (Cute Chess, Banksia, Arena, …).

Notes for testers

• 100% own network. nn-rubicon-v1.nnue is our own NNUE (own lineage), not a Stockfish net. Big-net-only by default (UseSmallNet off).
• Strength vs 4.1: the own network costs about −39 Elo vs the Stockfish-net 4.1 at 12+0.12 — the deliberate, accepted price of a fully own-lineage build. Search and speed are unchanged.
• Eval retuned for the new net: the NNUE post-processing constants were re-tuned (SPSA) for rubicon, since a different network wants a different eval-search coupling.
• Built with clang-cl + ThinLTO + profile-guided optimization.

License

GPLv3. The NNUE inference code (sfnnue/) is derived from Stockfish (GPLv3) and the whole project is distributed under the GPLv3; the network weights are our own. Full source in this repository.