Reconfigurable and Energy-Efficient Architecture for Deploying Multi-Layer RNNs on FPGA

Recurrent Neural Networks (RNNs) are extensively applied in sequence prediction tasks such as sentiment analysis, and machine translation. Long Short-Term Memory (LSTM) and Gated Recurrent Unit (GRU) are popular recurrent layers for mitigating gradient vanishing challenges. This paper introduces a reconfigurable hardware architecture that supports LSTM, GRU, and Fully Connected (FC) layers to accommodate the diverse structures of RNNs with minimal overhead. The proposed three-mode architecture utilizes dynamically reconfigurable components, allowing seamless mode switching among the three types of layers. Besides, Dynamic Compression (DC) for intermediate results is introduced to minimize precision loss, and layer decomposition as well as processing element grouping techniques are used to improve the processing efficiency. To validate the proposed architecture, a proof-of-concept prototype system using Intel Arria10 FPGA is built. Evaluation results demonstrate a 12% improvement over the state-of-the-art accelerator in energy efficiency when configured as GRU with a layer size set to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$512{\times }$ </tex-math></inline-formula> 512, accompanied by a 93% reduction in block RAM and an 81% reduction in DSP resources.