Generating Coupling Interfaces for Multiphysics Simulations with ExaStencils and waLBerla

Domain-specific languages (DSLs) and code generation technology are adopted more and more by the high performance computing (HPC) community to tackle the performance, portability, and productivity requirements for HPC software. They share their inherent specialization in specific scientific domains with traditional HPC frameworks. In this regard, multiphysics simulations pose a strong challenge as they usually require components from multiple domains. A promising option for retaining these requirements is the combination of code generation with HPC frameworks through automatically created couplings. This work demonstrates the fusion of waLBerla with generated code from ExaStencils. waLBerla is a massively parallel C++ framework focused on computational fluid dynamics (CFD) simulations using the Lattice Boltzmann method (LBM). ExaStencils generates whole simulation codes using geometric multigrid solvers from specifications in its own DSL. We showcase the coupling of generated solvers with LBM simulations, including the mapping of data structures and augmentations to convert quantities units on-the-fly.