ReViT: Vision Transformer Accelerator With Reconfigurable Semantic-Aware Differential Attention

While vision transformers (ViTs) have continued to achieve new milestones in computer vision, their complicated network architectures with high computation and memory costs have hindered their deployment on resource-limited edge devices. Some customized accelerators have been proposed to accelerate the execution of ViTs, achieving improved performance with reduced energy consumption. However, these approaches utilize flattened attention mechanisms and ignore the inherent hierarchical visual semantics in images. In this work, we conduct a thorough analysis of hierarchical visual semantics in real-world images, revealing opportunities and challenges of leveraging visual semantics to accelerate ViTs. We propose ReViT, a systematic algorithm and architecture co-design approach, which aims to exploit the visual semantics to accelerate ViTs. Our proposed algorithm can leverage the same semantic class with strong feature similarity to reduce computation and communication in a differential attention mechanism, and support the semantic-aware attention efficiently. A novel dedicated architecture is designed to support the proposed algorithm and translate it into performance improvements. Moreover, we propose an efficient execution dataflow to alleviate workload imbalance and maximize hardware utilization. ReViT opens new directions for accelerating ViTs by exploring the underlying visual semantics of images. ReViT gains an average of 2.3$\boldsymbol{\times}$ speedup and 3.6$\boldsymbol{\times}$ energy efficiency over state-of-the-art ViT accelerators.