Semi-lagrangian formulations with automatic code generation for environmental modeling

An import issue for numerical weather prediction modes (NWP) is the time it takes to produce a valid forecast. One factor, which greatly influences this simulation time is the size of the time step. However, time step size is often limited by the numerical stability of the used advection schemes. Available schemes include semiimplicit Eulerian and semi-Lagrangian schemes. In principal, semi-Lagrangian formulations result in irregular communications on parallel architectures. In this paper we describe automatic code generation for a semi-implicit scheme with a semi-Lagrangian formulation. We describe how code can be generated from a mathematical specification of the advection model, the embedding of the formulations in the CTADEL code generation tool and we show the parallelization of the code. Finally, we show results from preliminary experiments we have conducted with the generated code and the reference code from a production NWP on a number of different architectures