Uni-Encoder: A Fast and Accurate Response Selection Paradigm for Generation-Based Dialogue Systems

Chiyu Song, Hongliang He, Haofei Yu, Pengfei Fang, Leyang Cui, Zhenzhong Lan


Abstract
Sample-and-rank is a key decoding strategy for modern generation-based dialogue systems. It helps achieve diverse and high-quality responses by selecting an answer from a small pool of generated candidates. The current state-of-the-art ranking methods mainly use an encoding paradigm called Cross-Encoder, which separately encodes each context-candidate pair and ranks the candidates according to their fitness scores. However, Cross-Encoder repeatedly encodes the same lengthy context for each candidate, resulting in high computational costs. Poly-Encoder addresses the above problems by reducing the interaction between context and candidates, but with a price of performance drop. In this work, we develop a new paradigm called Uni-Encoder, that keeps the full attention over each pair as in Cross-Encoder while only encoding the context once, as in Poly-Encoder. Uni-Encoder encodes all the candidates with the context in one forward pass. We use the same positional embedding for all candidates to ensure they are treated equally and design a new attention mechanism to avoid confusion. Our Uni-Encoder can simulate other ranking paradigms using different attention and response concatenation methods. Extensive experiments show that our proposed paradigm achieves new state-of-the-art results on four benchmark datasets with high computational efficiency. For instance, it improves R10@1 by 2.9% with an approximately 4X faster inference speed on the Ubuntu V2 dataset.
Anthology ID:
2023.findings-acl.388
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:
6231–6244
Language:
URL:
https://aclanthology.org/2023.findings-acl.388
DOI:
10.18653/v1/2023.findings-acl.388
Bibkey:
Cite (ACL):
Chiyu Song, Hongliang He, Haofei Yu, Pengfei Fang, Leyang Cui, and Zhenzhong Lan. 2023. Uni-Encoder: A Fast and Accurate Response Selection Paradigm for Generation-Based Dialogue Systems. In Findings of the Association for Computational Linguistics: ACL 2023, pages 6231–6244, Toronto, Canada. Association for Computational Linguistics.
Cite (Informal):
Uni-Encoder: A Fast and Accurate Response Selection Paradigm for Generation-Based Dialogue Systems (Song et al., Findings 2023)
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PDF:
https://aclanthology.org/2023.findings-acl.388.pdf