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Efficient Large Language Model Based Passage Re-Ranking Using Single Token Representations
Jeongwoo Na, Jun Kwon, Eunseong Choi, Jongwuk Lee
http://doi.org/10.5626/JOK.2025.52.5.395
In information retrieval systems, document re-ranking involves reordering a set of candidate documents based on evaluation of their relevance to a given query. Leveraging extensive natural language understanding capabilities of large language models(LLMs), numerous studies on document re-ranking have been conducted, demonstrating groundbreaking performance. However, studies utilizing large language models focus solely on improving reranking performance, resulting in degraded efficiency due to excessively long input sequences and the need for repetitive inference. To address these limitations, we propose ListT5++, a novel model that represents the relevance between a query and a passage using single token embedding and significantly improves the efficiency of LLM-based reranking through a single-step decoding strategy that minimizes the decoding process. Experimental results showed that ListT5++ could maintain accuracy levels comparable to existing methods while reducing inference latency by a factor of 29.4 relative to the baseline. Moreover, our approach demonstrates robust characteristics by being insensitive to th initial ordering of candidate documents, thereby ensuring high practicality in real-time retrieval environments.
Multi-task Learning Based Re-ranker for External Knowledge Retrieval in Document-grounded Dialogue Systems
http://doi.org/10.5626/JOK.2023.50.7.606
Document-grounded dialogue systems retrieve external passages related to the dialogue and use them to generate an appropriate response to the user"s utterance. However, the retriever based on the dual-encoder architecture records low performance in finding relevant passages, and the re-ranker to complement the retriever is not sufficiently optimized. In this paper, to solve these problems and perform effective external passage retrieval, we propose a re-ranker based on multi-task learning. The proposed model is a cross-encoder structure that simultaneously learns contrastive learning-based ranking, Masked Language Model (MLM), and Posterior Differential Regularization (PDR) in the fine-tuning stage, enhancing language understanding ability and robustness of the model through auxiliary tasks of MLM and PDR. Evaluation results on the Multidoc2dial dataset show that the proposed model outperforms the baseline model in Recall@1, Recall@5, and Recall@10.
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