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ValuSpec drops weak branches before tree-based speculative decoding verifies them, for up to 2.78x end-to-end speedup

AspireAI community · arXiv (He, Ma, Zhan, Fan, Cao, Lan, Kang, Wang)
*Speculative decoding gets less efficient exactly when it gets more useful.* Tree-based speculative decoding verifies many candidate branches in parallel, and in serving traffic where similar requests repeat, retrieved draft trees fill up with low-quality branches that waste target-model compute. ValuSpec is a plug-and-play filter: it estimates a threshold from the target model's own greedy trajectories on a calibration split, with no parameter training, and drops branches the target is unlikely to accept - while the greedy verification rule keeps accepted tokens identical to standard autoregressive decoding. On HumanEval, GSM8K, Dolly and SpecBench it reached up to 2.38x end-to-end speedup in retrieval-based tree settings, and up to 2.78x when dropped into EAGLE-3's dynamic tree framework without changing how that framework builds its trees. Caveat: these are 'up to' numbers reported by the authors on their own evaluation setup, and ValuSpec is a research prototype rather than a released serving component. https://arxiv.org/abs/2610.31338
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