Conditional independence limits parallel token generation in masked diffusion models

alec_helbling · x · 2026-09-05

A technical thread explains masked diffusion models' core limitation: tokens sampled in the same step are conditionally independent, so each marginal can look sensible while the joint sequence is incoherent (e.g. "Alice won after Alice resigned"). Structured tasks like Sudoku therefore need few interdependent tokens per pass, limiting parallel-generation speedups.

Related event: Why Parallel Generation Struggles: Masked Diffusion Models' Coherence Problem(3 posts)→

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