Enhancing Transformer-Based Rerankers with Synthetic Data and LLM-Based Supervision

Dimitar Peshevski, Kiril Blazhevski, Martin Popovski, Gjorgji Madjarov


Abstract
Effective document reranking is essential for improving search relevance across diverse applications. While Large Language Models (LLMs) excel at reranking due to their deep semantic understanding and reasoning, their high computational cost makes them impractical for many real-world deployments. Fine-tuning smaller, task-specific models is a more efficient alternative but typically depends on scarce, manually labeled data. To overcome this, we propose a novel pipeline that eliminates the need for human-labeled query-document pairs. Our method uses LLMs to generate synthetic queries from domain-specific corpora and employs an LLM-based classifier to label positive and hard-negative pairs. This synthetic dataset is then used to fine-tune a smaller transformer model with contrastive learning using Localized Contrastive Estimation (LCE) loss. Experiments on the MedQuAD dataset show that our approach significantly boosts in-domain performance and generalizes well to out-of-domain tasks. By using LLMs for data generation and supervision rather than inference, we reduce computational costs while maintaining strong reranking capabilities.
Anthology ID:
2025.ranlp-1.109
Volume:
Proceedings of the 15th International Conference on Recent Advances in Natural Language Processing - Natural Language Processing in the Generative AI Era
Month:
September
Year:
2025
Address:
Varna, Bulgaria
Editors:
Galia Angelova, Maria Kunilovskaya, Marie Escribe, Ruslan Mitkov
Venue:
RANLP
SIG:
Publisher:
INCOMA Ltd., Shoumen, Bulgaria
Note:
Pages:
953–961
Language:
URL:
https://aclanthology.org/2025.ranlp-1.109/
DOI:
Bibkey:
Cite (ACL):
Dimitar Peshevski, Kiril Blazhevski, Martin Popovski, and Gjorgji Madjarov. 2025. Enhancing Transformer-Based Rerankers with Synthetic Data and LLM-Based Supervision. In Proceedings of the 15th International Conference on Recent Advances in Natural Language Processing - Natural Language Processing in the Generative AI Era, pages 953–961, Varna, Bulgaria. INCOMA Ltd., Shoumen, Bulgaria.
Cite (Informal):
Enhancing Transformer-Based Rerankers with Synthetic Data and LLM-Based Supervision (Peshevski et al., RANLP 2025)
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PDF:
https://aclanthology.org/2025.ranlp-1.109.pdf