Speaker
Description
In this talk, we plan to report the results of our performance optimisation effort aimed at speeding up a GPU-accelerated 2D Particle-in-Cell plasma simulation code, following an international plasma simulation benchmarking effort of 19 leading plasma research groups. We studied the effects of memory management, data movements, the choice and implementation of the Poisson solver, the use of mixed precision computation and various kernel-level optimisation techniques. Finally, the optimised version was improved to support multi-GPU execution as well. The key steps of the optimisation, the performance critical factors and our decisions will be presented in detail in the talk. Compared to the original baseline version that executed the simulation in 10 days, the runtime was reduced to less than 10 hours on an NVIDIA A100 GPU. Taking into account the performance increase of each new generation of GPU cards (from P100 to A100) as well, the overall speedup achieved with the optimised version exceeds 30×. The multi-GPU implementation will further reduce the execution time; using 4 A100 GPUs, we expect the final runtime to be less than 3 hours (note: final steps of the implementation and testing are currently underway, exact timings will be presented at the conference), that will make our implementation the fastest Penning discharge simulation code available. This level of performance not only means that we can execute simulations within a few hours instead of several days or weeks on GPUs, but it also allows for tackling large and complex simulation problems that were previously thought to be impossible to execute.