Practical Computational Power of Linear Transformers and Their Recurrent and Self-Referential Extensions

Kazuki Irie, Róbert Csordás, Jürgen Schmidhuber


Abstract
Recent studies of the computational power of recurrent neural networks (RNNs) reveal a hierarchy of RNN architectures, given real-time and finite-precision assumptions. Here we study auto-regressive Transformers with linearised attention, a.k.a. linear Transformers (LTs) or Fast Weight Programmers (FWPs). LTs are special in the sense that they are equivalent to RNN-like sequence processors with a fixed-size state, while they can also be expressed as the now-popular self-attention networks. We show that many well-known results for the standard Transformer directly transfer to LTs/FWPs. Our formal language recognition experiments demonstrate how recently proposed FWP extensions such as recurrent FWPs and self-referential weight matrices successfully overcome certain limitations of the LT, e.g., allowing for generalisation on the parity problem. Our code is public.
Anthology ID:
2023.emnlp-main.588
Volume:
Proceedings of the 2023 Conference on Empirical Methods in Natural Language Processing
Month:
December
Year:
2023
Address:
Singapore
Editors:
Houda Bouamor, Juan Pino, Kalika Bali
Venue:
EMNLP
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
9455–9465
Language:
URL:
https://aclanthology.org/2023.emnlp-main.588
DOI:
10.18653/v1/2023.emnlp-main.588
Bibkey:
Cite (ACL):
Kazuki Irie, Róbert Csordás, and Jürgen Schmidhuber. 2023. Practical Computational Power of Linear Transformers and Their Recurrent and Self-Referential Extensions. In Proceedings of the 2023 Conference on Empirical Methods in Natural Language Processing, pages 9455–9465, Singapore. Association for Computational Linguistics.
Cite (Informal):
Practical Computational Power of Linear Transformers and Their Recurrent and Self-Referential Extensions (Irie et al., EMNLP 2023)
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PDF:
https://aclanthology.org/2023.emnlp-main.588.pdf
Video:
 https://aclanthology.org/2023.emnlp-main.588.mp4