Benchmark of the high-resolution Nemo-SI3-XIOS configuration SEDNA on an ARM-based HPC system, Fugaku.

<p>We have developed the ocean-sea ice Arctic regional configuration <strong>SEDNA</strong> (Sea ice - EDdy resolving ocean paN-Arctic configuration) at ultra-high resolution (800&#160;m in the horizontal and 150 vertical levels) based on the NEMO-SI3 numerical platform, in order to investigate how the dynamics of mesoscale turbulent eddies in the Arctic Ocean interplay with sea ice.&#160;</p><p>The configuration was initially developed on the <strong>AMD-</strong>based HPC system <strong>Joliot-Curie ROME </strong>based at CEA in France<strong>, </strong>which has achieved a Linpack performance of 12 PFlop/s ranked number&#160;33 of June 2020 TOP500 list (https://top500.org/system/179700/).</p><p>Thanks to a European PRACE allocation of nearly 40 million CPU hours, we were able to run a 8 year-long simulation. Although promising to understand part of the small-scale dynamics at play, this length of simulation will likely be a limiting factor in the investigation of the eddy dynamics which is known to equilibrate over several decades.</p><p>To overcome this limitation, here we investigate the feasibility of running SEDNA over several decades but at a realistic time cost. To that aim, a benchmark has been performed on the <strong>ARM</strong> based HPC system <strong>Fugaku </strong>based at RIKEN in Japan, which has archived a Linpack performance of 442 PFlop/s ranked number&#160;1 of November 2020 TOP500 list (https://www.top500.org/system/179807/). Such a benchmark has required adaptation of the compiling and placements of NEMO and XIOS MPI processes in order to fit on the Fugaku architecture compared to standard X86_64 based HPC systems like Joliot-Curie ROME. In this presentation we will share the tips and lessons learned from our benchmarks and will report the benchmark results.&#160; Our insights on model MPI placements for efficient post processing of huge models will be discussed as well.</p>