Heterogeneous edge platforms enable the efficient execution of machine learning inference applications. These applications often have a critical constraint (such as meeting a deadline) and an optimization goal (such as minimizing energy consumption). To navigate this space, existing optimization frameworks adjust the platform's frequency configuration for the CPU, the GPU and/or the memory controller. However, existing optimization frameworks have two limitations. First, edge applications are frequently deployed in environments where they are exposed to ambient temperature variations. Second, a recent study has shown that temperature has a significant impact on edge platform characteristics. In this context, today's frequency optimization frameworks (which are thermal-oblivious) select frequency configurations that either violate the application's constraints, or are sub-optimal in terms of the optimization goal.

This study offers a methodology to characterize intra- and inter-node variability and applies it on two heterogeneous edge platforms (the NVIDIA Jetson AGX and Nano) for performance and power consumption. Firstly, we explore intra-node variability: investigate to what degree deployment decisions can limit it, highlight that it is unavoidable, and offer a scale so that one can compare to what other studies report. Secondly, we characterize inter-node variability by answering two questions: (i) Are the platforms we study statistically different in terms of the applications' power draw and runtime? and (ii) What is the magnitude of these differences? Finally, we attempt to answer the question of why is it paramount to characterize variability and take it into account? to achieve this, we discuss examples from the compiler and runtime optimization domains.