Multigrid solvers

Nodal projection

The following inputs are defined using the nodal_proj prefix.

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 allow in 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

MAC projection

The following inputs are defined using the mac_proj prefix.

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

Diffusion

The following inputs are defined using the diffusion prefix.

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

Hypre Settings

hypre settings are specified using the following inputs which are read directly by AMReX when hypre is used as the bottom solve for the MAC and/or nodal projections. By default, these inputs are defined using the hypre prefix, however different settings for the nodal and MAC projections can be used by specifying a hpyre_namespace for each solver.

Warning

  • MFIX-Exa must be built with hypre enabled to use hypre as the bottom solve.

  • If hypre is used for the nodal and MAC projections, then either the hypre_namespace must be left as the default (hypre) or unique name spaces must be provided for both.

These inputs follow the typical approach for using hypre in MFIX-Exa where BoomerAMG is employed as a preconditioner and GMRES for the linear solver.

Description

Type

Default

hypre_preconditioner

Type of preconditioner

Options are BoomerAMG or euclid

string

none

recompute_preconditioner

Recompute preconditioner during runs

Bool

true

hypre_solver

Type of hypre solver

Options are BoomerAMG, GMRES, COGMRES, LGMRES, FlexGMRES, BiCGSTAB, PCG or Hybrid

string

BoomerAMG

verbose

Verbosity of hypre

int

0

num_krylov

Number of iterations

int

50

The following inputs are valid when using BoomerAMG as a preconditioner or solver.

Description

Type

Default

bamg_verbose

Set BoomerAMG verbosity

int

0

bamg_logging

See HYPRE_BoomerAMGSetLogging

int

0

bamg_max_iterations

See HYPRE_BoomerAMGSetMaxIter

int

1

bamg_precond_tolerance

See HYPRE_BoomerAMGSetTol

Real

0.0

bamg_coarsen_type

See HYPRE_BoomerAMGSetCoarsenType

int

6

bamg_cycle_type

See HYPRE_BoomerAMGSetCycleType

int

1

bamg_relax_order

See HYPRE_BoomerAMGSetRelaxOrder

int

1

bamg_relax_type

See HYPRE_BoomerAMGSetRelaxType

int

6

bamg_down_relax_type

See HYPRE_BoomerAMGSetCycleRelaxType

int

11

bamg_up_relax_type

See HYPRE_BoomerAMGSetCycleRelaxType

int

11

bamg_coarse_relax_type

See HYPRE_BoomerAMGSetCycleRelaxType

int

11

bamg_num_sweeps

See HYPRE_BoomerAMGSetNumSweeps

int

2

bamg_num_down_sweeps

See HYPRE_BoomerAMGSetCycleNumSweeps

int

2

bamg_num_up_sweeps

See HYPRE_BoomerAMGSetCycleNumSweeps

int

2

bamg_num_coarse_sweeps

See HYPRE_BoomerAMGSetCycleNumSweeps

int

1

bamg_max_levels

See HYPRE_BoomerAMGSetMaxLevels

int

20

bamg_strong_threshold

See HYPRE_BoomerAMGSetStrongThreshold

Real

0.57

bamg_interp_type

See HYPRE_BoomerAMGSetInterpType

int

0

bamg_variant

See HYPRE_BoomerAMGSetVariant

int

0

bamg_keep_transpose

See HYPRE_BoomerAMGSetKeepTranspose

int

0

bamg_min_coarse_size

See HYPRE_BoomerAMGSetMinCoarseSize

int

1

bamg_max_coarse_size

See HYPRE_BoomerAMGSetMaxCoarseSize

int

9

bamg_pmax_elmts

See HYPRE_BoomerAMGSetPMaxElmts

int

4

bamg_agg_num_levels

See HYPRE_BoomerAMGSetAggNumLevels

int

0

bamg_agg_interp_type

See HYPRE_BoomerAMGSetAggInterpType

int

4

bamg_agg_pmax_elmts

See HYPRE_BoomerAMGSetAggPMaxElmts

int

0

bamg_trunc_factor

See HYPRE_BoomerAMGSetTruncFactor

Real

0.1

bamg_set_restriction

See HYPRE_BoomerAMGSetRestriction

int

0

Description

Type

Default

adjust_singular_matrix

Should be true if the problem to be solved has singular matrix

Bool

false

overwrite_existing_matrix_files

Over-write existing matrix files

Bool

false

write_matrix_files

Write out matrix into text files

Bool

false

Note

This list is likely incomplete because the AMReX / hypre interface continues to evolve.