Optimizing Test-Time Query Representations for Dense Retrieval

Mujeen Sung, Jungsoo Park, Jaewoo Kang, Danqi Chen, Jinhyuk Lee


Abstract
Recent developments of dense retrieval rely on quality representations of queries and contexts from pre-trained query and context encoders. In this paper, we introduce TOUR (Test-Time Optimization of Query Representations), which further optimizes instance-level query representations guided by signals from test-time retrieval results. We leverage a cross-encoder re-ranker to provide fine-grained pseudo labels over retrieval results and iteratively optimize query representations with gradient descent. Our theoretical analysis reveals that TOUR can be viewed as a generalization of the classical Rocchio algorithm for pseudo relevance feedback, and we present two variants that leverage pseudo-labels as hard binary or soft continuous labels. We first apply TOUR on phrase retrieval with our proposed phrase re-ranker, and also evaluate its effectiveness on passage retrieval with an off-the-shelf re-ranker. TOUR greatly improves end-to-end open-domain question answering accuracy, as well as passage retrieval performance. TOUR also consistently improves direct re-ranking by up to 2.0% while running 1.3–2.4x faster with an efficient implementation.
Anthology ID:
2023.findings-acl.354
Volume:
Findings of the Association for Computational Linguistics: ACL 2023
Month:
July
Year:
2023
Address:
Toronto, Canada
Editors:
Anna Rogers, Jordan Boyd-Graber, Naoaki Okazaki
Venue:
Findings
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
5731–5746
Language:
URL:
https://aclanthology.org/2023.findings-acl.354
DOI:
10.18653/v1/2023.findings-acl.354
Bibkey:
Cite (ACL):
Mujeen Sung, Jungsoo Park, Jaewoo Kang, Danqi Chen, and Jinhyuk Lee. 2023. Optimizing Test-Time Query Representations for Dense Retrieval. In Findings of the Association for Computational Linguistics: ACL 2023, pages 5731–5746, Toronto, Canada. Association for Computational Linguistics.
Cite (Informal):
Optimizing Test-Time Query Representations for Dense Retrieval (Sung et al., Findings 2023)
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PDF:
https://aclanthology.org/2023.findings-acl.354.pdf
Video:
 https://aclanthology.org/2023.findings-acl.354.mp4