Multigrid Inputs

Below is a list of the most commonly used multigrid settings options. To control the nodal projection precede with “nodal_proj”, for the MAC projection use “mac_proj”, and for the diffusion solvers use “scalar_diffusion” (tracers, temperature and the component-wise velocity solve) or “tensor_diffusion” (the tensor velocity solve). The diffusion solvers read the verbosity and iteration keys with an “mg_” prefix: mg_verbose, mg_bottom_verbose, mg_max_iter, mg_bottom_maxiter, mg_maxorder.

	Description	Type	Default
verbose	Verbosity of multigrid solver	Int	0
bottom_verbose	Verbosity of BiCGStab solver	Int	0
mg_rtol	Relative tolerance	Real float	1.e-11 1.e-4
mg_atol	Absolute tolerance	Real float	1.e-14 1.e-7
maxiter	Maximum number of iterations (diffusion: mg_max_iter)	Int	nodal 100 MAC 200 diffusion 100
bottom_maxiter	Maximum number of iterations in the bottom solver if using bicg, cg, bicgcg or cgbicg (diffusion: mg_bottom_maxiter)	Int	nodal 100 MAC 200 diffusion 100
mg_max_coarsening_level	Maximum number of coarser levels to allow. If set to 0, the bottom solver will be called at the current level	Int	100
bottom_solver	Which bottom solver to use. Options are bicgcg, bicgstab, cg, cgbicg, smoother or hypre	String	bicgcg

See AMReX-Hydro’s documentation on projections inputs for additional projection options.