On the Inevitability of Integrated HPC Systems and How they will Change HPC System Operations

High-Performance Computing (HPC) is at an inflection point in its evolution. General-purpose architectures approach limits in terms of speed and power/energy, requiring the development of specialized architectures to deliver accelerated performance. Additionally, the arrival of new user communities and workloads---including machine learning, data analytics, and quantum simulation---increases the breadth of application characteristics we need to support, putting pressure on the complexity of the architectural portfolio. At the same time, data movement has been identified as a main culprit of energy waste, pushing hardware designers towards a tighter integration of the different technologies. The resulting integrated systems offer great opportunities in terms of power/performance tradeoffs, but also lead to challenges on the software side. In this position paper, we highlight the trends leading us to integrated systems and describe their substantial advantages over simpler, single accelerated designs. Further, we highlight its impact on the corresponding software stack and its challenges and impact on the user. This introduces a different way to design, program, and operate HPC systems, and ultimately to the need to drop some long-held dogmas or believes in HPC systems.