Skip to content

Release 3.3: Syzygy tablebases, illegal-position crash fix, LMR revert

Choose a tag to compare

View all tags
@Tors3 Tors3 released this 29 May 14:09
· 50 commits to main since this release
v3.3
37daad7

Triumviratus 3.3 Hybrid

Triumviratus 3.3 is a UCI chess engine (~3450+ Elo, CCRL scale) combining alpha-beta search, NNUE evaluation, an experimental policy network, and ABDADA parallel SMP. This release adds Syzygy endgame tablebase support and fixes a crash on illegal positions.

Highlights

  • Syzygy tablebases — perfect endgame play: WDL probing in search + DTZ probing at the root (converts wins / holds draws). Tables up to 5 men, via Fathom.
  • Crash fix — eliminated an access violation (0xC0000005) on illegal / king-capture positions parsed from FEN.
  • More robust search — history-based LMR reverted to the conservative ±1-ply clamp after match testing.

Full Changelog

  • Add Syzygy tablebase probing (Fathom): in-search WDL + root DTZ, auto-loaded from a Syzygy/ folder next to the executable or via the SyzygyPath UCI option.
  • Fix access violation on positions where the side-not-to-move is in check: guard td_negamax_abdada / td_quiescence against searching illegal king-capture positions.
  • Revert combined butterfly+continuation-history LMR to butterfly-only ±1-ply clamp.
  • Bump version to 3.3 (UCI id name + startup banner).
  • Build output renamed to Triumviratus_3.3.exe.
  • Updated README.md and FIXES_DOCUMENTATION.md.

Download & Setup

Place these files in the same directory as Triumviratus_3.3.exe:

  • nn-b1a57edbea57.nnue (Big Net)
  • nn-baff1ede1f90.nnue (Small Net)
  • triumviratus_policy.bin (Policy Network weights)

Optional, for tablebase support: put your Syzygy .rtbw/.rtbz files in a folder and set the SyzygyPath UCI option to its absolute path (a Syzygy/ folder next to the exe is auto-detected). Setting SyzygyPath explicitly is recommended, since some GUIs launch the engine from a different working directory.

Recommended UCI options

  • Hash: 1024 MB or more for long time controls.
  • Threads: match your hardware.
  • SyzygyPath: absolute path to your tablebase folder (empty = disabled).
  • UsePolicy: false by default; true enables the experimental policy network.

Build

Visual Studio 2022 (toolset v143), Release | x64 — already configured for /O2, AVX2, intrinsics and LTCG:

& "C:\Program Files\Microsoft Visual Studio\2022\Community\MSBuild\Current\Bin\MSBuild.exe" `
  "Triumviratus_3.0.vcxproj" /t:Rebuild /p:Configuration=Release /p:Platform=x64

Requires an AVX2-capable CPU.

Known Issues

  • A very rare (~1 in 400 games) illegal-move / disconnect anomaly has been observed in self-play and is under investigation; it affects both sides equally and does not bias match results. Tournament PGNs are being collected to reproduce it.
Assets 4
Loading