arXiv Machine Learning By Vansh Bansal, Cholyeon Cho, Syamantak Kumar, Sujay Sanghavi, Purnamrita Sarkar

Walk fast but be careful: Understanding Parallel Sampling in Masked Diffusion

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The paper introduces random walks on graphs as a controllable sandbox for studying parallel sampling strategies in masked diffusion models (MDMs). It shows that common parallel unmasking methods, such as lowest‑entropy scoring, are not universally superior to random sampling and that performance depends on the graph’s conditional dependence structure. The authors also propose training‑free bisection samplers that are provably exact for random walks and demonstrate their effectiveness on both graph‑walk tasks and pretrained MDMs for language generation and reasoning benchmarks.

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