@inproceedings{ichihara-etal-2025-theoretical,
    title = "Theoretical Guarantees for Minimum {B}ayes Risk Decoding",
    author = "Ichihara, Yuki  and
      Jinnai, Yuu  and
      Ariu, Kaito  and
      Morimura, Tetsuro  and
      Uchibe, Eiji",
    editor = "Che, Wanxiang  and
      Nabende, Joyce  and
      Shutova, Ekaterina  and
      Pilehvar, Mohammad Taher",
    booktitle = "Proceedings of the 63rd Annual Meeting of the Association for Computational Linguistics (Volume 1: Long Papers)",
    month = jul,
    year = "2025",
    address = "Vienna, Austria",
    publisher = "Association for Computational Linguistics",
    url = "https://preview.aclanthology.org/ingestion-acl-25/2025.acl-long.793/",
    pages = "16262--16284",
    ISBN = "979-8-89176-251-0",
    abstract = "Minimum Bayes Risk (MBR) decoding optimizes output selection by maximizing the expected utility value of an underlying human distribution. While prior work has shown the effectiveness of MBR decoding through empirical evaluation, few studies have analytically investigated why the method is effective. As a result of our analysis, we show that, given the size $n$ of the reference hypothesis set used in computation, MBR decoding approaches the optimal solution with high probability at a rate of $\mathcal{O}(n^{-\frac{1}{2}})$, under certain assumptions, even though the language space $\mathcal{Y}$ is significantly larger $|\mathcal{Y}| \gg n$.This result helps to theoretically explain the strong performance observed in several prior empirical studies on MBR decoding. In addition, we provide the performance gap for maximum-a-posteriori (MAP) decoding and compare it to MBR decoding. The result of this paper indicates that MBR decoding tends to converge to the optimal solution faster than MAP decoding in several cases."
}