Gridding and Load Balancing¶
Nyx has a great deal of 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.
We use the phrase “load balancing” here to refer to the combined process of grid creation (and re-creation when regridding) and distribution of grids to MPI ranks.
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
We can also specify the strategy for assigning tiles to OpenMP threads.
See the AMReX documentation for more about tiling.