An Analytical Model of Configurable Systolic Arrays to find the Best-Fitting Accelerator for a given DNN Workload

Since their breakthrough, complexity of Deep Neural Networks (DNNs) is rising steadily. As a result, accelerators for DNNs are now used in many domains. However, designing and configuring an accelerator that meets the requirements of a given application perfectly is a challenging task. In this paper, we therefore present our approach to support the accelerator design process. With an analytical model of a systolic array we can estimate performance, energy consumption and area for each design option. To determine these metrics, usually a cycle accurate simulation is performed, which is a time-consuming task. Hence, the design space has to be restricted heavily. Analytical modelling, however, allows for fast evaluation of a design using a mathematical abstraction of the accelerator. For DNNs, this works especially well since the dataflow and memory accesses have high regularity. To show the correctness of our model, we perform an exemplary realization with the state-of-the-art systolic array generator Gemmini and compare it with a cycle accurate simulation and state-of-the-art modelling tools, showing less than 1% deviation. We also conducted a design space exploration, showing the analytical model’s capabilities to support an accelerator design. In a case study on ResNet-34, we can demonstrate that our model and DSE tool reduces the time to find the best-fitting solution by four or two orders of magnitude compared to a cycle-accurate simulation or state-of-the-art modelling tools, respectively.