Gabriel: a modern Fortran-library for simple, fast and verified exchange of halo regions

The Fortran language and the MPI standard are used by a large portion of computational fluid dynamics and climate models. Fortran has recently been expanded with features like object-oriented programming and assumed-rank arrays, while the MPI library received a major overhaul in MPI-3.0 with features like neighbor communicators and more derived types. Both developments can have a great impact in terms of programmability and performance of earth system models. The Gabriel library combines these recent developments into a library that improves the use of MPI for applications written (largely) in Fortran. Gabriel offers a high performance, verification and ease of use, especially for models on regular grids.