Scheduling diffusion LLMs by remaining work instead of arrival order cut mean end-to-end latency over SGLang by 5.4x on average and up to 14.9x
AspireAI community · arXiv
Diffusion language models decode by iteratively denoising many tokens in parallel, but serving frameworks schedule them with policies built for autoregressive models, where first-come-first-served and prefill priority both make sense. For diffusion LLMs they do not: arrival-order admission causes severe head-of-line blocking because decoding cost is heterogeneous and unknown at arrival, while prefill priority leaves most of the batch idle on prompt-only rounds. DWISE schedules by remaining work measured in a block-level unit shared by prefill and denoising, predicting it with a lightweight prompt-based predictor at admission plus one refinement from the first denoising round's hidden states. Implemented in SGLang and evaluated on five models from three diffusion-LLM families under bursty workloads, it reduced mean end-to-end latency by 5.4x on average and up to 14.9x while preserving task accuracy, with code stated to be on the way to public release. The gains come from scheduling rather than from making the models themselves faster.
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Two sparse-autoencoder analyses have resisted scaling: matching semantically similar features across layers, and compressing large feature circuits into interpretable supernodes. This paper argues both are the same underlying problem, estimating semantic distances between SAE features that sit on different activation manifolds. Its representation treats each feature not as a single decoder vector but as an activation-weighted distribution over the hidden states expressing it, projects those distributions into a shared reference space, and compares them with Wasserstein distance. The representation is proved invariant to activation rescaling and stable under perturbation, and recovers true matches under finite-sample margin conditions. Empirically it outperformed decoder-vector and LLM-based baselines and captured subtle functional distinctions between related features, and it compressed large feature circuits into interpretable supernodes automatically. The limitation is that this is interpretability tooling: the paper demonstrates better feature matching and circuit compression, not that downstream interpretability claims become more accurate.