Transformers are RNNs: Fast Autoregressive Transformers with Linear Attention
This addresses the speed bottleneck for transformers in tasks with very long sequences, such as language modeling or time-series prediction, though it is an incremental improvement on existing methods.
The paper tackled the quadratic complexity problem of transformers for long sequences by reformulating self-attention as a linear dot-product, reducing complexity from O(N^2) to O(N), resulting in up to 4000x faster autoregressive prediction with similar performance to vanilla transformers.
Transformers achieve remarkable performance in several tasks but due to their quadratic complexity, with respect to the input's length, they are prohibitively slow for very long sequences. To address this limitation, we express the self-attention as a linear dot-product of kernel feature maps and make use of the associativity property of matrix products to reduce the complexity from $\mathcal{O}\left(N^2\right)$ to $\mathcal{O}\left(N\right)$, where $N$ is the sequence length. We show that this formulation permits an iterative implementation that dramatically accelerates autoregressive transformers and reveals their relationship to recurrent neural networks. Our linear transformers achieve similar performance to vanilla transformers and they are up to 4000x faster on autoregressive prediction of very long sequences.