Wordfish is a free, open-source UCI chess engine implementing cutting-edge search algorithms combined with neural network evaluation. Derived from fundamental chess programming principles, Wordfish analyzes positions through parallelized alpha-beta search enhanced with null-move pruning and late move reductions.
Rating Chess Engines Diary CEDR=3755
Author: Jorge Ruiz Centelles and the Stockfish developers
Wordfish 4.90 1405 what's new?
What changed in Wordfish 4.90 (vs 4.80)
The default big NNUE net was updated again: EvalFileDefaultNameBig changed from nn-fcf986aea78a.nnue to nn-83a0d6daf7e5.nnue, aligned with the later Stockfish development line used for this release audit.
The small NNUE net was not changed: EvalFileDefaultNameSmall remains nn-47fc8b7fff06.nnue.
The Wordfish dual-network contract was preserved: Wordfish still keeps separate EvalFileDefaultNameBig and EvalFileDefaultNameSmall definitions. This release does not migrate Wordfish to a single-net macro structure.
Syzygy tablebase authority was protected: root positions governed by tablebase information are no longer allowed to be practically distorted by book, Experience, or auxiliary override paths.
Experience safety was tightened: Experience write/update behaviour is guarded so that tablebase-root or unreliable-result situations do not contaminate the learning record.
Book and tablebase interaction was corrected: book-root selection is not allowed to bypass tablebase authority in positions where Syzygy should be decisive for the root decision.
PolyGlot en-passant hashing was corrected: the book hashing path was audited so that en-passant state handling does not create incorrect PolyGlot keys in positions where the EP square should not contribute.
The auxiliary Zobrist helper was documented: Wordfish_zobrist.h is treated as an auxiliary Experience/book-support component and not as a replacement for the engine’s canonical internal Zobrist key system.
The public release identity was updated: the build identity is now Wordfish-4.90-140526. The existing architecture suffix model remains preserved for Windows EXE naming and UCI/GUI identification.
Compatibility note: this is not a blind upstream overwrite. It is a controlled Wordfish release combining a big-NNUE refresh with source-tree sanitation in the areas that can affect tablebase correctness, book-root behaviour, and Experience integrity.
Wordfish 4.50 190326 vs other engines:
| Stockfish dev-20260318 | 21/43 | -1 | 43 games |
| Stockfish 18 JA | 22.5/42 | +3 | 42 games |
| ShashChess 41 GoldDigger | 22/42 | +2 | 42 games |
| ShashChess 41 | 21/42 | +0 | 42 games |
| Brainlearn 31 | 21/42 | +0 | 42 games |
| Revolution 5.10 090326 | 11.5/23 | +0 | 23 games |
| DON dev-20260302 | 11/22 | +0 | 22 games |
| Sky Mini MPV | 10.5/22 | -1 | 22 games |
| Artemis 28.4TR PrO | 9/21 | -3 | 21 games |
| Sky | 11/20 | +2 | 20 games |
| CorChess 20260227 | 10.5/20 | +1 | 20 games |
| Hlamnick 090326 | 10.5/20 | +1 | 20 games |
| Revolution 5.0 030326 | 9.5/20 | -1 | 20 games |
| Reckless 0.10.0 | 1.5/3 | +0 | 3 games |
| Hlamnick 200326 | 1/3 | -1 | 3 games |
| Clover 9.1 JA | 1.5/2 | +1 | 2 games |
| PZChessBot 6.0 JA | 1.5/2 | +1 | 2 games |
| Quanticade 3.0 | 1.5/2 | +1 | 2 games |
| Pawnocchio 1.9.2 | 1.5/2 | +1 | 2 games |
| Caissa 1.24 JA | 1.5/2 | +1 | 2 games |
| DarkSeid 10.6 SE | 1.5/2 | +1 | 2 games |
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