Accelerated simulation of microwave breakdown in gases on Xeon Phi based cluster-application to self-organized plasma pattern formation

Modeling and simulation of high power microwave (HPM) breakdown, involving complex coupling between high frequency electromagnetic wave and plasma, is a computationally challenging and expensive problem due to the stringent numerical criteria. In this article, efficient parallelization and optimization strategies for two dimensional fluid simulation of microwave breakdown phenomena in air/gas on Intel's Xeon Phi Many Integrated Core (MIC) data parallel architecture are being presented. The numerical model used for this study is based on Finite Difference Time Domain solutions of Maxwell Equation coupled with the plasma fluid Continuity Equation (Boeuf et al., 2010). The optimized parallel version of this algorithm using OpenMP on Xeon Phi co-processors achieves a speedup of around 5-138 times (on Knights Corner and Knights Landing for different problem sizes) compared to a serial version (on Intel i7-4790 processor) in a much more energy efficient way. Moreover, a hybrid strategy based on OpenMP and MPI, involving a three-level parallelization (instruction level within SIMD VPUs, thread-level over many cores and accelerator level across a cluster of Xeon Phi processors), achieves a speedup of around 1400 (compared to a serial version on xeon-phi 7250 processor) on an HPC cluster with 24 Xeon-Phi co-processors. Several fast and accurate numerical experiments have been performed on the Xeon-Phi based system, and the results are illustrated with the example of the formation of a self-organized fishbone like plasma structure during breakdown similar to the images obtained from high power microwave experiments in air (Hidaka et al., 2008). Numerical experiments show that a good resource utilization can be achieved by proper code design, cache optimization and good programming practices, and opens up many possibilities for HPM breakdown research which require resource intensive EM-fluid simulations as a precursor at a relatively cheap cost.