What's the current strongest Chess Engine built solely on heuristics, no neural networks or any kind of deep learning?

1 Answer 1


The strongest classical chess engine is probably Stockfish classical, i.e. Stockfish with its NNUE turned off. I say this because Stockfish was leagues ahead of all its CPU rivals before the NNUE revolution, and after the NNUE revolution very few people are still working on classical engines, so it's unlikely anyone caught Stockfish. In fact, if you look at CCRL (Computer Chess Rating Lists), no classical engine has caught Houdini (all the engines above it are either NN or NNUE based).

  • 1
    What's Houdini?
    – minseong
    Jan 31, 2022 at 13:42
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    @theonlygusti a chess engine - cruxis.com/chess/houdini.htm. Do note Houdini is controversial, because it's allegedly a Stockfish clone.
    – Allure
    Jan 31, 2022 at 13:52
  • So by saying no classical engine has caught Houdini, you are saying that Stockfish is the strongest classical engine
    – minseong
    Jan 31, 2022 at 15:11
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    @theonlygusti Stockfish classical is significantly stronger than Houdini, and no classical engine has caught Houdini, let alone Stockfish classical.
    – Allure
    Jan 31, 2022 at 15:18
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    Houdini is arguably an older version of Stockfish classical, in particular Stockfish 8. The last version of Stockfish classical was somewhere after Stockfish 11 but before Stockfish 12.
    – Allure
    Jan 31, 2022 at 15:21

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