Addressing the issue of processing element under-utilization in general-purpose systolic deep learning accelerators.

As an energy-efficient hardware solution for deep neural network (DNN) inference, systolic accelerators are particularly popular in both embedded and datacenter computing scenarios. Despite their excellent performance and energy efficiency, however, systolic DNN accelerators are naturally facing a resource under-utilization problem - not all DNN models can well match the fixed processing elements (PEs) in a systolic array implementation, because typical DNN models vary significantly from applications to applications. Consequently, state-of-the-art hardware solutions are not expected to deliver the nominal (peak) performance and energy efficiency as claimed because of resource under-utilization. To deal with this dilemma, this study proposes a novel systolic DNN accelerator with a flexible computation mapping and dataflow scheme. By providing three types of parallelism and dynamically switching among them: channel-direction mapping, planar mapping, and hybrid, our accelerator offers the adaptability to match various DNN models to the fixed hardware resources, and thus, enables flexibly exploiting PE provision and data reuse for a wide range of DNN models to achieve optimal performance and energy efficiency.