[P] gumbel-mcts, a high-performance Gumbel MCTS implementation

Reddit r/MachineLearning / 3/26/2026

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Key Points

  • The author released an efficient Python/Numba implementation of Gumbel MCTS in the open-source repository gumbel-mcts after building a self-play environment from scratch for learning purposes.
  • Benchmarking against a “golden standard” baseline shows the provided PUCT implementation runs 2–15x faster while producing the exact same policy.
  • The release includes both dense and sparse versions of Gumbel MCTS, with the sparse variant intended to work well for games with very large action spaces such as chess.
  • The author claims Gumbel MCTS makes better use of low simulation budgets than PUCT, suggesting advantages in compute-constrained settings.
  • They invite community feedback, noting substantial manual validation effort in addition to using coding agents during development.

Hi folks,

Over the past few months, I built an efficient MCTS implementation in Python/numba.

https://github.com/olivkoch/gumbel-mcts

As I was building a self-play environment from scratch (for learning purposes), I realized that there were few efficient implementation of this algorithm.

I spent a lot of time validating it against a golden standard baseline.

My PUCT implementation is 2-15X faster than the baseline while providing the exact same policy.

I also implemented a Gumbel MCTS, both dense and sparse. The sparse version is useful for games with large action spaces such as chess.

Gumbel makes much better usage of low simulation budgets than PUCT.

Overall, I think this could be useful for the community. I used coding agents to help me along the way, but spent a significant amount of manual work to validate everything myself.

Feedback welcome.

submitted by /u/randomwalkin
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