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A budget-aware tree drafter for block diffusion reached a 6.61 times decoding speedup without training, and beat existing block-diffusion baselines by 39 percent

AspireAI community · arXiv
Bastion attacks a known weakness of block-diffusion drafters: their parallel token predictions come from position-wise marginals rather than a conditioned sequence, so committing to one greedy path often misses the target model's preferred trajectory. It builds a query-dependent draft tree on the fly, balancing draft quality against hardware limits through an acceptance surrogate, an online latency estimator calibrated against a roofline model, and a best-first expansion that stops when marginal gains no longer justify verification cost. The method is training-free, preserves the target model's distribution, and needs no per-setting tuning, and the authors report speedups up to 6.61 times over standard autoregressive decoding, 39 percent ahead of state-of-the-art block-diffusion baselines across diverse benchmarks and GPU architectures. The limitation worth keeping in view is that the speedup depends on having a diffusion-style drafter to begin with, so it does not transfer to the plain autoregressive models most serving stacks run today.
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One distance function matched sparse-autoencoder features across layers and compressed feature circuits into supernodes
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.
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