RACER: Retrieval-Augmented Contextual Rapid Speculative Decoding

• URL: http://arxiv.org/abs/2604.14885v1
• Date: Thu, 16 Apr 2026 11:23:55 GMT
• Title: RACER: Retrieval-Augmented Contextual Rapid Speculative Decoding
• Abstract summary: Autoregressive decoding in Large Language Models (LLMs) generates one token per step, causing high inference latency.<n>We propose $textbfRACER, a lightweight and training-free method that integrates retrieved exact patterns with logit-driven future cues.<n>Experiments on Spec-Bench, HumanEval, and MGSM-ZH demonstrate that RACER consistently accelerates inference, achieving more than $2times$ speedup over autoregressive decoding.
• Score: 80.12789199134511
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Autoregressive decoding in Large Language Models (LLMs) generates one token per step, causing high inference latency. Speculative decoding (SD) mitigates this through a guess-and-verify strategy, but existing training-free variants face trade-offs: retrieval-based drafts break when no exact match exists, while logits-based drafts lack structural guidance. We propose $\textbf{RACER}$ ($\textbf{R}$etrieval-$\textbf{A}$ugmented $\textbf{C}$ont$\textbf{e}$xtual $\textbf{R}$apid Speculative Decoding), a lightweight and training-free method that integrates retrieved exact patterns with logit-driven future cues. This unification supplies both reliable anchors and flexible extrapolation, yielding richer speculative drafts. Experiments on Spec-Bench, HumanEval, and MGSM-ZH demonstrate that RACER consistently accelerates inference, achieving more than $2\times$ speedup over autoregressive decoding, and outperforms prior training-free methods, offering a scalable, plug-and-play solution for efficient LLM decoding. Our source code is available at $\href{https://github.com/hkr04/RACER}{https://github.com/hkr04/RACER}$.

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