Towards Efficient Linear Scaling Green Function DFT Calculations

Materials research is an area that is expected to strongly benefit from the growing performance capabilities of future supercomputers towards Exascale. Density functional theory (DFT) has become one of the most important methods for numerical materials science. In this talk I present a methodology for restructuring a scalable DFT application for the efficient usage of current and future HPC systems based on many core architectures. Particular focus is set to Xeon Phis and GPU-accelerated systems since large HPC installations in the pre-Exascale range are planned and the compute capabilities of the first machine reaching 1 ExaFlop/s is likely to consist of one of these architectures. For the purpose of tuning and testing, a mini-app has been extracted that replays the most performance critical kernel. Inside the kernel routine, a reordering algorithm is promising to boost the performance by reducing the bandwidth requirements of a large number of small matrix-matrix multiplications