Simulation of extreme-scale homogeneous turbulence on a new leadership Exascale GPU platform

Fluid turbulence is a major domain-science problem where high-resolution simulations with trillions of grid points are a powerful research tool. We focus on Exascale-ready GPU algorithm development based on Fourier pseudo-spectral methods suitable for homogeneous turbulence in three-dimensional space. The overall goal is to push the envelope in simulation size while optimizing aggressively for reasonable time to solution. Fast computation on GPUs, efficient data movement between host and device, as well as highly-scalable communication are all crucial for best performance. Use of the latest OpenMP standard promotes inter-platform portability, although machine characteristics still have a strong influence on key programming strategies. Specific issues include the dimensionality of the domain decomposition, collective message-passing via the host or device, efficient host and device memory utilization and opportunities for asynchronism. We shall provide a status report on both the full turbulence simulation code and a 3D FFT kernel of more general interest, on hardware similar to one of the world's first Exascale machines.