Efficient Beam Search for Large Language Models Using Trie-Based Decoding
Brian J Chan, Mao-xun Huang, Jui-Hung Cheng, Chao-Ting Chen, Hen-Hsen Huang
Abstract
This work presents a novel trie (prefix-tree)-based parallel decoding method that addresses the memory inefficiency of batch-based beam search. By sharing a single KV cache across beams with common prefixes, our approach dramatically reduces memory usage and enables efficient decoding. We evaluated our method across three attention architectures, Multi-Head Attention (Phi-3.5-mini-instruct), Grouped Query Attention (Llama-3.1-8B-Instruct), and Sliding Window Attention (Mistral-Small-24B-Instruct-2501), using CNN/DailyMail for abstractive summarization and HumanEval for code generation. Our experiments demonstrate substantial memory savings (4–8×) and up to 2.4× faster decoding, without compromising generation quality. These results highlight our method’s suitability for memory-constrained environments and large-scale deployments.- Anthology ID:
- 2025.emnlp-main.748
- Volume:
- Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing
- Month:
- November
- Year:
- 2025
- Address:
- Suzhou, China
- Editors:
- Christos Christodoulopoulos, Tanmoy Chakraborty, Carolyn Rose, Violet Peng
- Venue:
- EMNLP
- SIG:
- Publisher:
- Association for Computational Linguistics
- Note:
- Pages:
- 14806–14818
- Language:
- URL:
- https://preview.aclanthology.org/ingest-emnlp/2025.emnlp-main.748/
- DOI:
- Cite (ACL):
- Brian J Chan, Mao-xun Huang, Jui-Hung Cheng, Chao-Ting Chen, and Hen-Hsen Huang. 2025. Efficient Beam Search for Large Language Models Using Trie-Based Decoding. In Proceedings of the 2025 Conference on Empirical Methods in Natural Language Processing, pages 14806–14818, Suzhou, China. Association for Computational Linguistics.
- Cite (Informal):
- Efficient Beam Search for Large Language Models Using Trie-Based Decoding (Chan et al., EMNLP 2025)
- PDF:
- https://preview.aclanthology.org/ingest-emnlp/2025.emnlp-main.748.pdf