Development of communication overlap techniques for Peta-scale gyrokinetic simulations

Idomura, Yasuhiro   ; Nakata, Motoki; Yamada, Susumu  ; Machida, Masahiko  ; Imamura, Toshiyuki*

Gyrokinetic simulations are essential and powerful tools in studying turbulent transport in fusion plasmas. In order to enhance the capabilities of gyrokinetic simulations, further improvements both in simulation models and in computing power are needed. In particular, the plasma size scaling of turbulent transport is one of critical issues, which require extreme scale computing. However, it is not so easy to extract high computing power from modern Peta-scale supercomputers because of (1) very complicated hierarchy of core, CPU, node, and network architectures, (2) extreme concurrency beyond 100k cores. In order to satisfy these technical needs, novel parallel computing techniques are developed on a gyrokinetic toroidal 5D Eulerian code GT5D.