LMUFormer: Low Complexity Yet Powerful Spiking Model With Legendre
  Memory Units
Zeyu Liu Gourav Datta Anni Li Peter Anthony Beerel
Transformer models have demonstrated high accuracy in numerous applications
but have high complexity and lack sequential processing capability making them
ill-suited for many streaming applications at the edge where devices are
heavily resource-constrained. Thus motivated, many researchers have proposed
reformulating the transformer models as RNN modules which modify the
self-attention computation with explicit states. However, these approaches
often incur significant performance degradation. The ultimate goal is to
develop a model that has the following properties: parallel training, streaming
and low-cost inference, and SOTA performance. In this paper, we propose a new
direction to achieve this goal. We show how architectural modifications to a
recurrent model can help push its performance toward Transformer models while
retaining its sequential processing capability. Specifically, inspired by the
recent success of Legendre Memory Units (LMU) in sequence learning tasks, we
propose LMUFormer, which augments the LMU with convolutional patch embedding
and convolutional channel mixer. Moreover, we present a spiking version of this
architecture, which introduces the benefit of states within the patch embedding
and channel mixer modules while simultaneously reducing the computing
complexity. We evaluated our architectures on multiple sequence datasets. In
comparison to SOTA transformer-based models within the ANN domain on the SCv2
dataset, our LMUFormer demonstrates comparable performance while necessitating
a remarkable 53 times reduction in parameters and a substantial 65 times
decrement in FLOPs. Additionally, owing to our model's proficiency in real-time
data processing, we can achieve a 32.03% reduction in sequence length, all
while incurring an inconsequential decline in performance. Our code is publicly
available at https://github.com/zeyuliu1037/LMUFormer.git.