RMT: Retentive Networks Meet Vision Transformers
Authors: Qihang Fan, Huaibo Huang, Mingrui Chen, Hongmin Liu, Ran He

Vision Transformer (ViT) has gained increasing attention in the computer vision community in recent years. However the core component of ViT Self-Attention lacks explicit spatial priors and bears a quadratic computational complexity thereby constraining the applicability of ViT. To alleviate these issues we draw inspiration from the recent Retentive Network (RetNet) in the field of NLP and propose RMT a strong vision backbone with explicit spatial prior for general purposes. Specifically we extend the RetNet's temporal decay mechanism to the spatial domain and propose a spatial decay matrix based on the Manhattan distance to introduce the explicit spatial prior to Self-Attention. Additionally an attention decomposition form that adeptly adapts to explicit spatial prior is proposed aiming to reduce the computational burden of modeling global information without disrupting the spatial decay matrix. Based on the spatial decay matrix and the attention decomposition form we can flexibly integrate explicit spatial prior into the vision backbone with linear complexity. Extensive experiments demonstrate that RMT exhibits exceptional performance across various vision tasks. Specifically without extra training data RMT achieves 84.8% and 86.1% top-1 acc on ImageNet-1k with 27M/4.5GFLOPs and 96M/18.2GFLOPs. For downstream tasks RMT achieves 54.5 box AP and 47.2 mask AP on the COCO detection task and 52.8 mIoU on the ADE20K semantic segmentation task.