Performance of real space Quantum Monte Carlo and QMCPACK on GPU accelerated Exascale supercomputers

We report the performance of real space quantum Monte Carlo calculations performed with QMCPACK for materials on NVIDIA and AMD GPUs, as found in latest generation of supercomputers. Over the last few years QMCPACK (https://www.qmcpack.org) developers have developed a new performance portable design that enables efficient support for both CPU and GPU accelerated systems from a largely common set of code paths. The design supports full fallback to CPU execution where features have not been ported to or optimized for GPUs. Here we report the performance obtained for a wide range of system sizes and discuss approaches to extend the complexity of materials that can be efficiently studied within current memory limits. The experiences are expected to be broadly relevant to other electronic structure codes and algorithms.