Gridding and Load Balancing

incflo leverages AMReX’s flexibility when it comes to how to decompose the computational domain into individual rectangular grids, and how to distribute those grids to MPI ranks. There can be grids of different sizes, more than one grid per MPI rank, and different strategies for distributing the grids to MPI ranks.

AMReX’s docmumentation on Gridding and Load Balancing contains further details. See Grid Creation for grids are created, i.e. how the BoxArray on which MultiFabs will be built is defined at each level. See Load Balancing for the strategies AMReX supports for distributing grids to MPI ranks, i.e. defining the DistributionMapping with which MultiFabs at that level will be built.

When running on multicore machines with OpenMP, we can also control the distribution of work by setting the size of grid tiles (by defining fabarray.mfiter_tile_size). We can also specify the strategy for assigning tiles to OpenMP threads. See MFIter with Tiling for more about tiling.