Exploring EC-Earth 3.2-Beta performance on the new ECMWF Cray-Broadwell

EC-Earth is a state-of-the-art earth system model composed with multiple elements. In this report we focus on the climate system parts of the 3.2beta release which consists of the IFS atmospheric model, NEMO version 3.6 as ocean circulation model which is interfaced with the LIM3 sea-ice model and a river Runoff mapper. These components are linked via the OASIS3-MCT coupler and use the XIOS for the IO management.

 The EC-Earth 3.2beta is ported to the new Broadwell-based High Performance Computing Facility of the ECMWF using both the Intel and the Cray compilers. The performance of the coupled system is assessed and shows that, in general the use of the Cray compiler can result in an increase in the system performance up to 34%. Recommendable configurations for the number of MPI tasks to use for each components are suggested based on scaling experiments. It is also shown that compared to the Ivy-Bridge-based machine, the new Broadwell-based machine would allow the EC-Earth consortium to benefit from more extensive resources without losing in term of running speed.