A roadmap for research in sustainable ultrascale systems

Europe has made impressive progress in different High Performance Computing (HPC) research areas that are crucial for the goals of the H2020 framework and beyond. This includes also the organization building of the European HPC community in general and network of sustainable ultrascale computing systems in particular. The ultimate goal is to pursue European HPC leadership on a unified basis, expanding the scientific and industrial access to and use of supercomputers, and launching initiatives to strengthen the European HPC supply chain toward a sustainable ultrascale computing systems. As a result, to achieve the designated goals, there is an urgent need for the European HPC research community to have a clear roadmap for the next stage: short-term, mid-term, and long-term perspectives. The objective of this research roadmap is to provide the readers with a set of research recommendations identified by COST Action IC1305, Network of Sustainable Ultrascale Computing Systems (NESUS), as key for achieving the ambitious goals set out in the Action. As such, this research roadmap paper aims at providing Sustainable Ultrascale Computing Systems input to the relevant stakeholders (H2020 Work Programme, ESF, COST programme leaders, industry, ...). The content presented in this research roadmap is the result of wide discussions within NESUS. It aggregates the input provided by NESUS Members, obtained through working groups meetings, online consultation, and discussion by the Management Committee of the Action. Relevant challenges and opportunities for Sustainable Ultrascale System are identified in this document as as large-scale complex systems joining parallel and distributed computing systems that will be two to three orders of magnitude larger that today s systems. The COST Action IC1035 (NESUS) proposes in this research roadmap six key objectives and twelve associated recommendations, which in combination, can help bring about the notable changes required to make true the existence of sustainable ultrascale computing systems. Moreover, they could be useful for industry and stakeholders to define a path towards ultrascale systems. A possible short and midterm research plan, that could be implemented in the EU to achieve those objectives and recommendations, is also proposed to coordinate European efforts for proposing realistic solutions addressing major challenges of building sustainable ultrascale computing systems. This research plan should be centered on the development of software and applications for Ultrascale Computing Systems, which should be a priority given that Europe is a strong partner in software for HPC and distributed systems, while it is not a leader hardware for large-scale software systems