Speaker
Description
Particle-in-Cell (PIC) simulation is an important tool in plasma science, where certain properties and behaviour can only be examined by simulations. Due to the large number of particles and simulation cycles, these simulations are extremely time-consuming and can be executed in acceptable time only with parallel implementations. A crucial step in the simulation is solving the Poisson equation to calculate the electric field that provides the basis of interactions among the particles. In this talk, we describe the design, implementation and performance optimisation of a multigrid iterative and a Fast Fourier Transform (FFT) based direct spectral solver for two-dimensional simulations. These algorithms aim to drastically improve the runtime performance of an already existing GPU-accelerated 2D PIC implementation. Compared with our original Discrete Fourier Transform based direct solver, the multigrid version achieved a near 10x speedup and the FFT version achieved 280x speedup for the frequently used grid size of 255×255 with similar results for other grid sizes up to 1023×1023. We present the performance analysis of the baseline implementation, the design details of our new implementations including the key decisions regarding algorithmic improvements and the used optimisation techniques for efficient use of the available GPU computational resources. In conclusion, the achieved runtime performance and numerical accuracy of the two implementations will be presented and compared against the baseline implementation.