Energy efficiency is an important aspect of future exascale systems, mainly due to rising energy cost. Although High performance computing (HPC) applications are compute centric, they still exhibit varying computational characteristics in different regions of the program, such as compute-, memory-, and I/O-bound code regions. Some of today's clusters already offer mechanisms to adjust the system to the resource requirements of an application, e.g., by controlling the CPU frequency. However, manually tuning for improved energy efficiency is a tedious and painstaking task that is often neglected by application developers. The European Union's Horizon 2020 project READEX (Runtime Exploitation of Application Dynamism for Energyefficient eXascale computing) aims at developing a tools-aided approach for improved energy efficiency of current and future HPC applications. To reach this goal, the READEX project combines technologies from two ends of the compute spectrum, embedded systems and HPC, constituting a split design-time/runtime methodology. dynamic auto-tuning of fine-grained application regions using the systems scenario methodology, which was originally developed for improving the energy efficiency in embedded systems. This paper introduces the concepts of the READEX project, its envisioned implementation, and preliminary results that demonstrate the feasibility of this approach.

Summary To overcome the challenges of energy consumption of HPC systems, the European Union Horizon 2020 READEX (Runtime Exploitation of Application Dynamism for Energy‐efficient Exascale computing) project uses an online auto‐tuning approach to improve energy efficiency of HPC applications. The READEX methodology pre‐computes optimal system configurations at design‐time, such as the CPU frequency, for instances of program regions and switches at runtime to the configuration given in the tuning model when the region is executed. READEX goes beyond previous approaches by exploiting dynamic changes of a region's characteristics by leveraging region and characteristic specific system configurations. While the tool suite supports an automatic approach, specifying domain knowledge such as the structure and characteristics of the application and application tuning parameters can significantly help to create a more refined tuning model. This paper presents the means available for an application expert to provide domain knowledge and presents tuning results for some benchmarks.

e European Union Horizon 2020 READEX project is developing a tool suite for dynamic energy tuning of HPC applications. e tool suite performs an analysis during design-time before production run to construct a tuning model encapsulated with the best-found con gurations that are then fed to the runtime tuning library. e library switches the con gurations at runtime to adapt the application for energy-e ciency. CCS CONCEPTS •Computer systems organization → Parallel architectures; •Hardware → Power and energy; •So ware and its engineering → Development frameworks and environments;

The main objective of this work is to design and construct a PoE switch based system: to control electric appliances such as light, fan, heater, washing machine, motor, TV, etc. and

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