Parallelization on a Hybrid Architecture of GBS, a Simulation Code for Plasma Turbulence at the Edge of Fusion Devices

We present recent developments of GBS, a simulation code used to evolve plasma turbulence in the edge of fusion devices. GBS solves a set of 3D fluid equations, the Poisson and the Ampere equation, and a kinetic equation for the neutral atoms. Investigations carried out with GBS have significantly advanced our understanding of the plasma dynamics at the edge of fusion devices. For example, GBS simulations allowed the identification of the turbulent regimes and the saturation mechanisms of the linearly unstable modes. In GBS, a 3D Cartesian MPI communicator is employed, leading to excellent parallel scalability up to 8192 cores. To efficiently exploit many-core and hybrid architectures, new schemes using MPI+OpenMP and MPI+OpenACC have been recently implemented. We show the implementation of the new parallelization schemes, their scalability, and their efficiency. The new parallelization allows the efficient use of advanced hybrid supercomputers, such as Piz Daint at CSCS.