ExaStencils: Advanced Multigrid Solver Generation

Present-day stencil codes are implemented in general-purpose programming languages, such as Fortran, C, or Java, Python or derivates thereof, and harnesses for parallelism, such as OpenMP, OpenCL or MPI. Project ExaStencils pursued a domain-specific approach with a language, called ExaSlang, that is stratified into four layers of abstraction, the most abstract being the formulation in continuous mathematics and the most concrete a full, automatically generated implementation. At every layer, the corresponding language expresses not only computational directives but also domain knowledge of the problem and platform to be leveraged for optimization. We describe the approach, the software technology behind it and several case studies that demonstrate its feasibility and versatility: high-performance stencil codes can be engineered, ported and optimized more easily and effectively.