Spliss: A Sparse Linear System Solver for Transparent Integration of Emerging HPC Technologies into CFD Solvers

Abstract

We introduce Spliss, a block sparse linear solver library, which is designed to meet current and upcoming challenges in the CFD development. The C++ template interface of Spliss supports a wide range of linear operators typically used in CFD applications. This includes sparse block matrices of fixed or variable block sizes, different scalar types and matrix-free operators. We explain the technical design of Spliss, by which we can achieve computational efficiency and parallel scalability on contemporary and emerging HPC platforms. The presented performance evaluation is conducted on the DLR cluster CARO and on Juwels Booster. It shows how we have passed the tipping point, beyond which GPUs perform strictly better, by integrating GPUDirect and CUDA-aware MPI communication.