Adaptive Block Diffusion: Resolving Training-Inference Mismatch in Diffusion Language Models
Diffusion Language Models face a fundamental gap between training and deployment: they're optimized for fixed token layouts but must handle arbitrary configurations at inference time, causing performance cliffs outside the training regime. Adaptive Block Diffusion addresses this by training across a distribution of prefix-window patterns, treating configuration as a learnable variable rather than a fixed constraint. The approach guarantees denoising optimality for any inference policy within the training distribution's support, eliminating architectural overhead. This matters because it unlocks flexible decoding strategies and scales DLM robustness without model redesign, potentially reshaping how generative language models handle variable-length and streaming inference.
Modelwire context
ExplainerThe core contribution is reframing inference configuration as a training variable rather than a post-hoc engineering choice, which means the model learns to be robust across deployment conditions rather than being patched after the fact. This is a training-time fix to a problem the field has mostly tried to solve at inference time.
This connects directly to the theme running through 'Beyond Trajectory Matching: Reflow with Marginal Distribution Alignment' from the same day, which identified a parallel problem in diffusion inference: optimizing for one objective during training (path matching) fails to constrain what actually matters at deployment (output distribution quality). Both papers are essentially arguing that the training objective must explicitly encode what you care about at inference, not assume it follows automatically. Together they suggest a broader reckoning in diffusion-based generation: the gap between how models are trained and how they are actually used is a first-class research problem, not an implementation detail to be tuned away.
Watch whether downstream DLM benchmarks, particularly on streaming or variable-length tasks, show consistent gains when Adaptive Block Diffusion training is applied to existing architectures without modification. If gains appear only on configurations within the explicit training distribution, the 'any inference policy' optimality claim needs closer scrutiny.
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MentionsDiffusion Language Models · Adaptive Block Diffusion
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