ScaFES: An Open-Source Framework for Explicit Solvers Combining High-Scalability with User-Friendliness

We present ScaFES, an open-source HPC framework written in C++11 for solving initial boundary value problems using explicit numerical methods in time on structured grids. It is designed to be highly-scalable and very user-friendly, i.e. to exploit all levels of parallelism and provide easy-to-use interfaces. Besides, the numerical nomenclature is reflected in a nearly oneto-one mapping. We describe how the framework works internally by presenting the core components of ScaFES, which modern C++ technologies are used, which parallelization methods are employed, and how the communication can be hidden behind during the update phase of a time step. Finally, we show how a multidimensional heat equation problem discretized via the finite difference method in space and via the explicit Euler scheme in time can be implemented and solved using ScaFES in about 60 lines. In order to demonstrate the excellent performance of ScaFES, we compare ScaFES to PETSc on the basis of the implemented heat equation example in two dimensions and present scalability results w.r.t. MPI and OpenMP achieved on HPC clusters at the ZIH.