Accelerating DNNs from local to virtualized FPGA in the Cloud: A survey of trends

Field-programmable gate arrays (FPGAs) are widely used locally to speed up deep neural network (DNN) algorithms with high computational throughput and energy efficiency. Virtualizing FPGA and deploying FPGAs in the cloud are becoming increasingly attractive methods for DNN acceleration because they can enhance the computing ability to achieve on-demand acceleration across multiple users. In the past five years, researchers have extensively investigated various directions of FPGA-based DNN accelerators, such as algorithm optimization, architecture exploration, capacity improvement, resource sharing, and cloud construction. However, previous DNN accelerator surveys mainly focused on optimizing the DNN performance on a local FPGA, ignoring the trend of placing DNN accelerators in the cloud's FPGA. In this study, we conducted an in-depth investigation of the technologies used in FPGA-based DNN accelerators, including but not limited to architectural design, optimization strategies, virtualization technologies, and cloud services. Additionally, we studied the evolution of DNN accelerators, e.g., from a single DNN to framework-generated DNNs, from physical to virtualized FPGAs, from local to the cloud, and from single-user to multi-tenant. We also identified significant obstacles for DNN acceleration in the cloud. This article enhances the current understanding of the evolution of FPGA-based DNN accelerators.