Large Language Models (LLMs) generate tokens autoregressively, with each token depending on the preceding context. This sequential nature makes the inference process inherently difficult to accelerate, posing a significant challenge for efficient deployment. In recent years, various methods have been proposed to address this issue, with the most effective approaches often involving the training of additional draft models. In this paper, we introduce READER (Retrieval-Assisted Drafter for Efficient LLM Inference), a novel lossless speculative decoding method that enhances model-based approaches by leveraging self-repetitions in the text. Our algorithm expands the speculative decoding tree using tokens obtained through statistical search. This work focuses on large batch sizes (>= 8), an underexplored yet important area for industrial applications. We also analyze the key-value (KV) cache size during speculative decoding and propose an optimization to improve performance for large batches. As a result, READER outperforms existing speculative decoding methods. Notably, READER requires no additional training and can reuse pre-trained speculator models, increasing the speedup by over 40\%. Our method demonstrates particularly strong performance on search-based tasks, such as retrieval-augmented generation, where we achieve more than 10x speedup.
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