Achieving Memory Scalability In The Gysela Code To Fit Exascale Constraints

Gyrokinetic simulations lead to huge computational needs. Up to now, the semi-Lagrangian code Gysela performed large simulations using a few thousands cores (65k cores). But to understand more accurately the nature of the plasma turbulence, finer resolutions are wished which make Gysela a good candidate to exploit the computational power of future Exascale machines. Among the Exascale challenges, the less memory per core issue is one of the must critical. This paper deals with memory management in order to reduce the memory peak, and presents an approach to understand the memory behaviour of an application when dealing with very large meshes. This enables us to extrapolate the behaviour of Gysela for expected capabilities of Exascale machine.