## Reformer: The Efficient Transformer

Sep 25, 2019 Blind Submission readers: everyone Show Bibtex
• Keywords: attention, locality sensitive hashing, reversible layers
• TL;DR: Efficient Transformer with locality-sensitive hashing and reversible layers
• Abstract: Large Transformer models routinely achieve state-of-the-art results on a number of tasks but training these models can be prohibitively costly, especially on long sequences. We introduce two techniques to improve the efficiency of Transformers. For one, we replace dot-product attention by one that uses locality-sensitive hashing, changing its complexity from O($L^2$) to O($L \log L$), where $L$ is the length of the sequence. Furthermore, we use reversible residual layers instead of the standard residuals, which allows storing activations only once in the training process instead of N times, where N is the number of layers. The resulting model, the Reformer, performs on par with Transformer models while being much more memory-efficient and much faster on long sequences.
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