Multigrid Inputs

The following inputs can be set directly in the AMReX solver classes but we set them via the MFIX-Exa routines because we may want different inputs for the different solvers called by MFIX-Exa. NOTE: the nodal solver settings are read in directly by AMReX, the MAC and diffusion settings by MFIX-Exa.

These control the nodal projection and must be preceded by “nodal_proj.”:

	Description	Type	Default
verbose	Verbosity of multigrid solver in nodal projection	Int	0
bottom_verbose	Verbosity of BiCGStab solver in nodal projection	Int	0
mg_rtol	Relative tolerance in nodal projection	Real	1.e-11
mg_atol	Absolute tolerance in nodal projection	Real	1.e-14
maxiter	Maximum number of iterations in the nodal projection	Int	100
bottom_maxiter	Maximum number of iterations in the nodal projection bottom solver if using bicg, cg, bicgcg or cgbicg	Int	100
mg_max_coarsening_level	Maximum number of coarser levels to allowin the nodal projection If set to 0, the bottom solver will be called at the current level	Int	100
bottom_solver	Which bottom solver to use in the nodal projection Options are bicgcg, bicgstab, cg, cgbicg, smoother or hypre	String	bicgcg
hypre_namespace	Namespace to use in the nodal projection when using hypre to control hypre specific settings. It can be any string.	String	hypre
hypre_interface	Which interface to use in the nodal projection when using hypre Options are ij, semi_structured or structured	String	ij

These control the MAC projection and must be preceded by “mac_proj.”:

	Description	Type	Default
verbose	Verbosity of multigrid solver in MAC projection	Int	0
bottom_verbose	Verbosity of BiCGStab solver in MAC projection	Int	0
mg_rtol	Relative tolerance in MAC projection	Real	1.e-11
mg_atol	Absolute tolerance in MAC projection	Real	1.e-14
maxiter	Maximum number of iterations in the MAC projection	Int	200
bottom_maxiter	Maximum number of iterations in the MAC projection bottom solver if using bicg, cg, bicgcg or cgbicg	Int	200
mg_max_coarsening_level	Maximum number of coarser levels to allow in the MAC projection If set to 0, the bottom solver will be called at the current level	Int	100
bottom_solver	Which bottom solver to use in the MAC projection Options are bicgcg, bicgstab, cg, cgbicg, smoother or hypre	String	bicgcg
hypre_namespace	Namespace to use in the MAC projection when using hypre to control hypre specific settings. It can be any string.	String	hypre
hypre_interface	Which interface to use in the MAC projection when using hypre Options are ij, semi_structured or structured	String	ij

NOTE: If the nodal_proj and mac_proj hypre_namespace’s are set, they must be distinct unless set to hypre, in which case the default behavior is recovered in which case hypre settings apply to all solvers.

These control the diffusion solver and must be preceded by “diffusion.”:

	Description	Type	Default
verbose	Verbosity of linear solver for diffusion solve	Int	0
bottom_verbose	Verbosity of BiCGStab solver in diffusion solve	Int	0
mg_rtol	Relative tolerance in diffusion solve	Real	1.e-11
mg_atol	Absolute tolerance in diffusion solve	Real	1.e-14
maxiter	Maximum number of iterations in diffusion solve	Int	100
bottom_maxiter	Maximum number of iterations in diffusion solve bottom solver if using bicg, cg, bicgcg or cgbicg	Int	100
mg_max_coarsening_level	Maximum number of coarser levels to allow in diffusion solve If set to 0, the bottom solver will be called at the current level	Int	100
bottom_solver	Which bottom solver to use in the diffusion solve Options are bicgcg, bicgstab, cg, cgbicg, or smoother	String	bicgcg