Скачать или смотреть Restructuring a Finite Element Magnetohydrodynamics MPI Code for GPU using OpenACC

The model of magnetohydrodynamics (MHD) has been used to calculate the macroscopic instabilities happening in thermonuclear fusion devices like National Spherical Torus Experiment (NSTX) and International Thermonuclear Experimental Reactor (ITER), and plays an important role in developing fusion power plants. M3D-C1, one of the flagship codes at Princeton Plasma Physics Laboratory (PPPL), is a code using finite element method to solve MHD equations and has been widely used in the community.

Having participated in two GPU Hackathons at Princeton University in 2019 and 2021, Chang Liu, staff research physicist at Princeton Plasma Physics Laboratory (PPPL), presents what was learned when porting this code to GPUs using OpenACC. Currently two parts of the code have been successfully ported, one is the calculation of finite element matrix, and the other is the particle-pushing in kinetic effect calculation. For the matrix calculation the team did a restructuring of the code to separate the physics part and the numerical integration part. The numerical part, which contains multi-layer nested loops, can run on GPUs efficiently thanks to OpenACC. The team also utilized the Multi-Process Service (MPS) developed by NVIDIA to make the MPI code work with multiple GPUs. For the second part, they utilized NVIDIA Nsight Systems to find the best strategy for parallelization for particle pushing. The speedup brought by the work for both parts are impressive.

Liu also talks about the remaining work to be done for porting the other parts of the code, including the iterative matrix solver and the reduction calculator of particle moments, and discusses the challenges associated with the work.