GPU-Acceleration of Large-Scale Full-Frequency GW Calculations

Many-body perturbation theory is a powerful method to simulate electronic excitations in molecules and materials starting from the output of density functional theory calculations. However, its widespread application to large systems has been hindered by the high computational cost. We present a GPU acceleration study of the full-frequency GW method for periodic systems, as implemented in the WEST code [http://west-code.org]. We discuss the use of (1) optimized GPU libraries, e.g., cuFFT and cuBLAS, (2) a hierarchical parallelization strategy that minimizes CPU-GPU, GPU-GPU, and CPU-CPU data transfer operations, (3) asynchronous GPU kernels that overlap with MPI communications, and (4) mixed precision in selected portions of the code. We demonstrate a substantial speedup of the GPU-accelerated version of WEST with respect to its CPU version, and we show good strong and weak scaling using up to 25,920 GPUs on the OLCF/Summit supercomputer. The GPU version of WEST yields electronic structures using the full-frequency GW method for realistic nanostructures and interfaces comprising up to 10,368 electrons. This work was supported by MICCoM, as part of the Computational Materials Sciences Program funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.