arXiv Machine Learning
Oct 16

Score Mismatch and Set-Constrained Sampling in Zero-Shot Conditional Discrete Diffusion

The paper presents a theoretical analysis of score mismatch in discrete diffusion models, deriving a KL divergence upper bound that quantifies the bias introduced when the training and target distributions differ. It examines partial-observation constraints such as text infilling and sentence completion, showing that the Conditional SEDD sampler can incur a bias that grows with dimension, vocabulary size, and compatibility. To mitigate this, the authors propose a Randomized Hard Clamping (RHC) sampler for coordinatewise set constraints, demonstrating through experiments that it effectively reduces bias and improves sampling performance.

By Renxiang Huang, Yuchen Liang, Yingbin Liang, Ness Shroff, Lifeng Lai