A New Traffic Offloading Method with Slow Switching Optical Device in Exascale Computer The expected exascale computer will comprise tens of thousands of computing nodes and nearly 5000 interconnected nodes in years to come. Such a largescale system will represent a milestone in the progress of HighPerformance Computing (HPC). The more efficient network hardware, like optoelectronic interconnection and configurable switches, is reforming the traditional architecture of supercomputers. However, the present architecture containing new hardware is not easy to adapt to the dynamically running condition, because the newly developed hardware is normally unable to effectively improve overall performance. Here, we propose a new accelerated system called Software Defined Network Accelerator (sDNA) for the exascale computer. Inspired by edge forwarding index (EFI), the main contribution of our work is that it presents an extended EFIbased optical interconnection method with slow switching optical device. The optical link is connected by the evaluation of each optical link candidateu0027s traffic offloading revenue. As the supporting method for optical interconnection, sDNA selects the most suitable routing configuration according to the jobschedule information and the priorknowledge of HPC applications. We tested sDNA in a network simulator and a prototype system for the exascale computer, using both DOE application benchmarks and a realworld communication benchmark. From the result of verification of traffic offloading, we found that our optical interconnection method based on our extended EFI evaluation is not only able to offload the traffic from an electrical link to an optical link but is also able to avoid congestion inherent to electrical link. Furthermore, our experimental results show that sDNA maintains the throughput of more than 80% bandwidth and reduced the communication delay by 10% in our real prototype system and simulator. Together, our sDNA is an ideal candidate for accelerating communication performance of the exascale computer.

Evaluating the Impact of Energy Efficient Networks on HPC Workloads Interconnection networks grow larger as supercomputers include more nodes and require higher bandwidth for performance. This scaling significantly increases the fraction of power consumed by the network, by increasing the number of network components (links and switches). Typically, network links consume power continuously once they are turned on. However, recent proposals for energy efficient interconnects have introduced lowpower operation modes for periods when network links are idle. Lowpower operation can increase messaging time when switching a link from lowpower to active operation. We extend the TraceRCODES network simulator for power modeling to evaluate the impact of energy efficient networking on power and performance. Our evaluation presents the first study on both singlejob and multijob execution to realistically simulate power consumption and performance under congestion for a largescale HPC network. Results on several workloads consisting of HPC proxy applications show that singlejob and multijob execution favor different modes of low power operation to have significant power savings at the cost of minimal performance degradation.