Steepest Guidance: A Practical and Principled Approach to Inference-Time Alignment of Flow and Diffusion-based Models

Abstract:Inference-time alignment of flow and diffusion-based models is critical for achieving flexible generative modeling. Theoretically, Doob's $h$-transform provides an elegant solution to this problem, and most existing methods are based on this principle. However, in practice, estimating the optimal guidance derived from Doob's $h$-transform at inference time is challenging. To deal with this issue, we regard inference-time alignment as a sequential optimization problem in the space of probability measures and propose a novel framework called *Steepest Guidance*, based on the principle of maximizing local improvement in the objective. We provide a theoretical analysis of the proposed method and demonstrate its effectiveness through extensive experiments.

Machine Learning (stat.ML); Machine Learning (cs.LG)

arXiv:2609.39091 [stat.ML]

(or arXiv:2609.39091v1 [stat.ML] for this version)

https://doi.org/10.48550/arXiv.2609.39091 Focus to learn more arXiv-issued DOI via DataCite (pending registration)

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