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 False

The following inputs must be preceded by “amrex.”

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

GPU memory

The following inputs must be preceded by “amrex.”

	Description	Type
the_arena_is_managed	Abort if an invalid floating point exception is encountered.	Int
the_arena_init_size	Abort if and overflow is detected.	Int
abort_on_out_of_gpu_memory	Abort if a division by zero is computed.	Int

Load balancing

Note that when running a granular simulation, i.e., no fluid phase, mfix.dual_grid must be 0. 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
dual_grid	If true then use the “dual_grid” approach for load balancing	Bool	False
regrid_int	How often to regrid (in number of steps at level 0) if regrid_int = -1 then no regridding will occur	Int	-1
load_balance_fluid	Only relevant if (dual_grid); if so do we also regrid mesh data	Int	0
load_balance_type	What strategy to use for load balancing Options are “KnapSack”, “SFC”, or “Greedy”	String	KnapSack
knapsack_weight_type	What weighting function to use if using Knapsack load balancing Options are “RunTimeCosts” or “NumParticles””	String	RunTimeCosts
knapsack_nmax	Maximum number of grids per MPI process if using knapsack algorithm	Int	128
greedy_dir	The direction in which the greedy algorithm cuts overloaded boxes	Int	0
greedy_min_grid_size	The minimum particle grid size in the greedy load balance algorithm	Int	2
greedy_3d	Partition particle grids in 3D with the greedy algorithhm	Bool	False
overload_tolerance*	The ratio between the maximum workload and the average workload in the greedy algorithm	Real	1.2
underload_tolerance*	The ratio between the minimum workload and the average workload in the greedy algorithm	Real	0.8
grid_pruning	Remove all covered grids from the base mesh; this may result in disjoined grids	Bool	False

* The greedy partitioning algorithm uses the tolerances to set the expected workload range for each rank but doesn’t strictly enforce them. The algorithm creates a partition as balance as possible even if the partition doesn’t meet the tolerances.

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