The Cascade Transformer: an Application for Efficient Answer Sentence Selection

Luca Soldaini, Alessandro Moschitti


Abstract
Large transformer-based language models have been shown to be very effective in many classification tasks. However, their computational complexity prevents their use in applications requiring the classification of a large set of candidates. While previous works have investigated approaches to reduce model size, relatively little attention has been paid to techniques to improve batch throughput during inference. In this paper, we introduce the Cascade Transformer, a simple yet effective technique to adapt transformer-based models into a cascade of rankers. Each ranker is used to prune a subset of candidates in a batch, thus dramatically increasing throughput at inference time. Partial encodings from the transformer model are shared among rerankers, providing further speed-up. When compared to a state-of-the-art transformer model, our approach reduces computation by 37% with almost no impact on accuracy, as measured on two English Question Answering datasets.
Anthology ID:
2020.acl-main.504
Volume:
Proceedings of the 58th Annual Meeting of the Association for Computational Linguistics
Month:
July
Year:
2020
Address:
Online
Venue:
ACL
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
5697–5708
Language:
URL:
https://aclanthology.org/2020.acl-main.504
DOI:
10.18653/v1/2020.acl-main.504
Bibkey:
Cite (ACL):
Luca Soldaini and Alessandro Moschitti. 2020. The Cascade Transformer: an Application for Efficient Answer Sentence Selection. In Proceedings of the 58th Annual Meeting of the Association for Computational Linguistics, pages 5697–5708, Online. Association for Computational Linguistics.
Cite (Informal):
The Cascade Transformer: an Application for Efficient Answer Sentence Selection (Soldaini & Moschitti, ACL 2020)
Copy Citation:
PDF:
https://preview.aclanthology.org/update-css-js/2020.acl-main.504.pdf
Video:
 http://slideslive.com/38929221
Code
 alexa/wqa-cascade-transformers
Data
ASNQNatural QuestionsTrecQAWikiQA