Advanced

Testing / debugging

The following inputs must be preceded by “mfix.”

	Description	Type	Default
verbose	Verbosity in MFIX-Exa routines	Int	0
ooo_debug	If true then print the name of the routine we are in	Bool	False
only_print_grid_report	Do not time-march the simulation. Simply generate the grid report and exit.	Bool	False

The following inputs must be preceded by “amrex.”

	Description	Type	Default
fpe_trap_invalid	Abort if an invalid floating point exception is encountered.	Int	0
fpe_trap_zero	Abort if a division by zero is computed.	Int	0
fpe_trap_overflow	Abort if an overflow is detected.	Int	0

GPU memory

The following inputs must be preceded by “amrex.”

	Description	Type	Default
the_arena_is_managed	Use managed memory for the main arena.	Int	0
the_arena_init_size	Main memory arena’s initial size in bytes.	Int	3/4 of system device memory
abort_on_out_of_gpu_memory	Abort if free device memory is less than the amount an arena is asked to allocate.	Int	0

Load balancing

Note that when running a granular simulation, i.e., no fluid phase, mfix.load_balance defaults to SingleGrid. Hence, the particles.max_grid_size (in each direction) have no meaning. Therefore the fluid grid and tile sizes should be set for particle load balancing. It may also be necessary to set the blocking factors to 1.

The following inputs must be preceded by mfix and determine how we load balance:

	Description	Type	Default
regrid_int	How often to regrid (in number of steps at level 0) if regrid_int <= 0 then no regridding will occur	int	0
load_balance	SingleGrid fluid and particles are co-located on the same grids DualGrid fluid and particles live on different grids	string	SingleGrid
load_balance.DualGrid.fluid	Regrid mesh (fluid) in addition to particles when using DualGrid	int	0
load_balance.strategy	What strategy to use for load balancing Options are KnapSack and SFC	string	KnapSack
load_balance.weighting	What weighting function to use if using Knapsack load balancing Options are ParticleRunTime, ParticleCount and CellCount	string	ParticleRunTime
knapsack_nmax	Maximum number of grids per MPI process if using knapsack algorithm	int	128
grid_pruning	Remove all covered grids from the base mesh; this may result in disjoined grids	bool	False

To allow a user to verify the breakdown of fluid grids created before running a full simulation, an input option, mfix.only_print_grid_report is supported. By default, it is False. When set to True, the run uses minimal memory to print the grid coverage report and exits immediately after that.

The following inputs are defined using the particles prefix.

	Description	Type	Default
max_grid_size_x	Maximum number of cells at level 0 in each grid in x-direction for grids in the ParticleBoxArray if dual_grid is true	Int	32
max_grid_size_y	Maximum number of cells at level 0 in each grid in y-direction for grids in the ParticleBoxArray if dual_grid is true	Int	32
max_grid_size_z	Maximum number of cells at level 0 in each grid in z-direction for grids in the ParticleBoxArray if dual_grid is true.	Int	32