MFEMTransient

Summary

Executioner for transient MFEM problems.

Overview

MFEMTransient is the Executioner class used to solve time dependent MFEM finite element problems, calling the MFEMProblemSolve solve object to execute one or more MFEM TimeDomainProblemOperators.

As in all Executioner classes using the MFEMProblemSolve solve object, the desired device and assembly level to use during problem set-up and solution can be selected.

Currently, only simulations with an implicit backwards Euler time integrator are supported. However, the TimeStepper system is fully supported providing wide choice for the timestep(s) dt.

Example Input File Syntax

[Executioner<<<{"href": "../../../syntax/Executioner/index.html"}>>>]
  type = MFEMTransient
  device = cpu
  assembly_level = legacy
  dt = 2.0
  start_time = 0.0
  end_time = 6.0
[]

Input Parameters

assembly_levellegacyMatrix assembly level.
Default:legacy
C++ Type:MooseEnum
Options:legacy, full, element, partial, none
Controllable:No
Description:Matrix assembly level.
deviceRun app on the chosen device.
C++ Type:std::string
Controllable:No
Description:Run app on the chosen device.
dt1The timestep size between solves
Default:1
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The timestep size between solves
end_time1e+30The end time of the simulation
Default:1e+30
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The end time of the simulation
error_on_dtminTrueThrow error when timestep is less than dtmin instead of just aborting solve.
Default:True
C++ Type:bool
Controllable:No
Description:Throw error when timestep is less than dtmin instead of just aborting solve.
num_steps4294967295The number of timesteps in a transient run
Default:4294967295
C++ Type:unsigned int
Controllable:No
Description:The number of timesteps in a transient run
reset_dtFalseUse when restarting a calculation to force a change in dt.
Default:False
C++ Type:bool
Controllable:No
Description:Use when restarting a calculation to force a change in dt.
schemeimplicit-eulerTime integration scheme used.
Default:implicit-euler
C++ Type:MooseEnum
Options:implicit-euler, explicit-euler, crank-nicolson, bdf2, explicit-midpoint, dirk, explicit-tvd-rk-2, newmark-beta
Controllable:No
Description:Time integration scheme used.
verboseFalseSet to true to print additional information
Default:False
C++ Type:bool
Controllable:No
Description:Set to true to print additional information

Optional Parameters

abort_on_solve_failFalseabort if solve not converged rather than cut timestep
Default:False
C++ Type:bool
Controllable:No
Description:abort if solve not converged rather than cut timestep
control_tagsAdds user-defined labels for accessing object parameters via control logic.
C++ Type:std::vector<std::string>
Controllable:No
Description:Adds user-defined labels for accessing object parameters via control logic.
dtmax1e+30The maximum timestep size in an adaptive run
Default:1e+30
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The maximum timestep size in an adaptive run
dtmin1e-12The minimum timestep size in an adaptive run
Default:1e-12
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The minimum timestep size in an adaptive run
n_startup_steps0The number of timesteps during startup
Default:0
C++ Type:int
Controllable:No
Description:The number of timesteps during startup
outputsVector of output names where you would like to restrict the output of variables(s) associated with this object
C++ Type:std::vector<OutputName>
Controllable:No
Description:Vector of output names where you would like to restrict the output of variables(s) associated with this object
start_time0The start time of the simulation
Default:0
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The start time of the simulation
timestep_tolerance1e-12the tolerance setting for final timestep size and sync times
Default:1e-12
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:the tolerance setting for final timestep size and sync times
use_multiapp_dtFalseIf true then the dt for the simulation will be chosen by the MultiApps. If false (the default) then the minimum over the master dt and the MultiApps is used
Default:False
C++ Type:bool
Controllable:No
Description:If true then the dt for the simulation will be chosen by the MultiApps. If false (the default) then the minimum over the master dt and the MultiApps is used

Advanced Parameters

accept_on_max_fixed_point_iterationFalseTrue to treat reaching the maximum number of fixed point iterations as converged.
Default:False
C++ Type:bool
Controllable:No
Description:True to treat reaching the maximum number of fixed point iterations as converged.
auto_advanceFalseWhether to automatically advance sub-applications regardless of whether their solve converges, for transient executioners only.
Default:False
C++ Type:bool
Controllable:No
Description:Whether to automatically advance sub-applications regardless of whether their solve converges, for transient executioners only.
custom_abs_tol1e-50The absolute nonlinear residual to shoot for during fixed point iterations. This check is performed based on postprocessor defined by the custom_pp residual.
Default:1e-50
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The absolute nonlinear residual to shoot for during fixed point iterations. This check is performed based on postprocessor defined by the custom_pp residual.
custom_ppPostprocessor for custom fixed point convergence check.
C++ Type:PostprocessorName
Unit:(no unit assumed)
Controllable:No
Description:Postprocessor for custom fixed point convergence check.
custom_rel_tol1e-08The relative nonlinear residual drop to shoot for during fixed point iterations. This check is performed based on the postprocessor defined by custom_pp residual.
Default:1e-08
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The relative nonlinear residual drop to shoot for during fixed point iterations. This check is performed based on the postprocessor defined by custom_pp residual.
direct_pp_valueFalseTrue to use direct postprocessor value (scaled by value on first iteration). False (default) to use difference in postprocessor value between fixed point iterations.
Default:False
C++ Type:bool
Controllable:No
Description:True to use direct postprocessor value (scaled by value on first iteration). False (default) to use difference in postprocessor value between fixed point iterations.
disable_fixed_point_residual_norm_checkFalseDisable the residual norm evaluation thus the three parameters fixed_point_rel_tol, fixed_point_abs_tol and fixed_point_force_norms.
Default:False
C++ Type:bool
Controllable:No
Description:Disable the residual norm evaluation thus the three parameters fixed_point_rel_tol, fixed_point_abs_tol and fixed_point_force_norms.
fixed_point_abs_tol1e-50The absolute nonlinear residual to shoot for during fixed point iterations. This check is performed based on the main app's nonlinear residual.
Default:1e-50
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The absolute nonlinear residual to shoot for during fixed point iterations. This check is performed based on the main app's nonlinear residual.
fixed_point_algorithmpicardThe fixed point algorithm to converge the sequence of problems.
Default:picard
C++ Type:MooseEnum
Options:picard, secant, steffensen
Controllable:No
Description:The fixed point algorithm to converge the sequence of problems.
fixed_point_force_normsFalseForce the evaluation of both the TIMESTEP_BEGIN and TIMESTEP_END norms regardless of the existence of active MultiApps with those execute_on flags, default: false.
Default:False
C++ Type:bool
Controllable:No
Description:Force the evaluation of both the TIMESTEP_BEGIN and TIMESTEP_END norms regardless of the existence of active MultiApps with those execute_on flags, default: false.
fixed_point_max_its1Specifies the maximum number of fixed point iterations.
Default:1
C++ Type:unsigned int
Controllable:No
Description:Specifies the maximum number of fixed point iterations.
fixed_point_min_its1Specifies the minimum number of fixed point iterations.
Default:1
C++ Type:unsigned int
Controllable:No
Description:Specifies the minimum number of fixed point iterations.
fixed_point_rel_tol1e-08The relative nonlinear residual drop to shoot for during fixed point iterations. This check is performed based on the main app's nonlinear residual.
Default:1e-08
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:The relative nonlinear residual drop to shoot for during fixed point iterations. This check is performed based on the main app's nonlinear residual.
multiapp_fixed_point_convergenceName of the Convergence object to use to assess convergence of the MultiApp fixed point solve. If not provided, a default Convergence will be constructed internally from the executioner parameters.
C++ Type:ConvergenceName
Controllable:No
Description:Name of the Convergence object to use to assess convergence of the MultiApp fixed point solve. If not provided, a default Convergence will be constructed internally from the executioner parameters.
relaxation_factor1Fraction of newly computed value to keep.Set between 0 and 2.
Default:1
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:Fraction of newly computed value to keep.Set between 0 and 2.
transformed_postprocessorsList of main app postprocessors to transform during fixed point iterations
C++ Type:std::vector<PostprocessorName>
Unit:(no unit assumed)
Controllable:No
Description:List of main app postprocessors to transform during fixed point iterations
transformed_variablesList of main app variables to transform during fixed point iterations
C++ Type:std::vector<std::string>
Controllable:No
Description:List of main app variables to transform during fixed point iterations

Fixed Point Iterations Parameters

check_auxFalseWhether to check the auxiliary system for convergence to steady-state. If false, then the solution vector from the solver system is used.
Default:False
C++ Type:bool
Controllable:No
Description:Whether to check the auxiliary system for convergence to steady-state. If false, then the solution vector from the solver system is used.
normalize_solution_diff_norm_by_dtTrueWhether to divide the solution difference norm by dt. If taking 'small' time steps you probably want this to be true. If taking very 'large' timesteps in an attempt to *reach* a steady-state, you probably want this parameter to be false.
Default:True
C++ Type:bool
Controllable:No
Description:Whether to divide the solution difference norm by dt. If taking 'small' time steps you probably want this to be true. If taking very 'large' timesteps in an attempt to *reach* a steady-state, you probably want this parameter to be false.
steady_state_convergenceName of the Convergence object to use to assess whether the solution has reached a steady state. If not provided, a default Convergence will be constructed internally from the executioner parameters.
C++ Type:ConvergenceName
Controllable:No
Description:Name of the Convergence object to use to assess whether the solution has reached a steady state. If not provided, a default Convergence will be constructed internally from the executioner parameters.
steady_state_detectionFalseWhether or not to check for steady state conditions
Default:False
C++ Type:bool
Controllable:No
Description:Whether or not to check for steady state conditions
steady_state_start_time0Minimum amount of time to run before checking for steady state conditions.
Default:0
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:Minimum amount of time to run before checking for steady state conditions.
steady_state_tolerance1e-08Whenever the relative residual changes by less than this the solution will be considered to be at steady state.
Default:1e-08
C++ Type:double
Unit:(no unit assumed)
Controllable:No
Description:Whenever the relative residual changes by less than this the solution will be considered to be at steady state.

Steady State Detection Parameters

max_xfem_update4294967295Maximum number of times to update XFEM crack topology in a step due to evolving cracks
Default:4294967295
C++ Type:unsigned int
Controllable:No
Description:Maximum number of times to update XFEM crack topology in a step due to evolving cracks
update_xfem_at_timestep_beginFalseShould XFEM update the mesh at the beginning of the timestep
Default:False
C++ Type:bool
Controllable:No
Description:Should XFEM update the mesh at the beginning of the timestep

Xfem Fixed Point Iterations Parameters

Restart Parameters

time_period_endsThe end times of time periods
C++ Type:std::vector<double>
Unit:(no unit assumed)
Controllable:No
Description:The end times of time periods
time_period_startsThe start times of time periods
C++ Type:std::vector<double>
Unit:(no unit assumed)
Controllable:No
Description:The start times of time periods
time_periodsThe names of periods
C++ Type:std::vector<std::string>
Controllable:No
Description:The names of periods

Time Periods Parameters

Input Files

(test/tests/mfem/multiapps/sub_cycling_sub.i)
(test/tests/mfem/variables/mfem_variables_from_moose.i)
(test/tests/mfem/multiapps/full_solve_parent.i)
(test/tests/mfem/multiapps/dt_from_parent.i)
(test/tests/mfem/multiapps/dt_from_parent_sub.i)
(test/tests/mfem/multiapps/full_solve_sub.i)
(test/tests/mfem/kernels/heattransfer.i)
(test/tests/mfem/multiapps/sub_cycling_parent.i)
(test/tests/mfem/timesteppers/mfem_multiple_timesequences.i)
(test/tests/mfem/timesteppers/mfem_multiple_timesteppers.i)
(test/tests/mfem/ics/transient_scalar_ic.i)

(test/tests/mfem/kernels/heattransfer.i)

[Mesh]
  type = MFEMMesh
  file = ../mesh/mug.e
  dim = 3
[]

[Problem]
  type = MFEMProblem
[]

[FESpaces]
  [H1FESpace]
    type = MFEMScalarFESpace
    fec_type = H1
    fec_order = FIRST
  []
[]

[Variables]
  [temperature]
    type = MFEMVariable
    fespace = H1FESpace
  []
[]

[AuxVariables]
  inactive = average_temperature
  [average_temperature]
    type = MFEMVariable
    fespace = H1FESpace
  []
[]

[AuxKernels]
  inactive = average_field
  [average_field]
    type = MFEMScalarTimeAverageAux
    variable = average_temperature
    source = temperature
  []
[]

[Kernels]
  [diff]
    type = MFEMDiffusionKernel
    variable = temperature
  []
  [dT_dt]
    type = MFEMTimeDerivativeMassKernel
    variable = temperature
  []
[]

[BCs]
  active = 'bottom top_convective'
  [bottom]
    type = MFEMScalarDirichletBC
    variable = temperature
    boundary = '1'
    coefficient = 1.0
  []
  [top_convective]
    type = MFEMConvectiveHeatFluxBC
    variable = temperature
    boundary = '2'
    T_infinity = .5
    heat_transfer_coefficient = 5
  []
  [top_dirichlet]
    type = MFEMScalarDirichletBC
    variable = temperature
    boundary = '2'
  []
[]

[Preconditioner]
  [boomeramg]
    type = MFEMHypreBoomerAMG
  []
  [jacobi]
    type = MFEMOperatorJacobiSmoother
  []
[]

[Solver]
  type = MFEMHypreGMRES
  preconditioner = boomeramg
  l_tol = 1e-16
  l_max_its = 1000
[]

[Executioner]
  type = MFEMTransient
  device = cpu
  assembly_level = legacy
  dt = 2.0
  start_time = 0.0
  end_time = 6.0
[]

[Outputs]
  [ParaViewDataCollection]
    type = MFEMParaViewDataCollection
    file_base = OutputData/HeatTransfer
    vtk_format = ASCII
  []
[]

(test/tests/mfem/multiapps/sub_cycling_sub.i)

[Problem]
  type = MFEMProblem
[]

[Mesh]
  type = MFEMMesh
  file = ../mesh/square.e
[]

[FESpaces]
  [H1FESpace]
    type = MFEMScalarFESpace
    fec_type = H1
    fec_order = FIRST
  []
[]

[Variables]
  [u]
    type = MFEMVariable
    fespace = H1FESpace
  []
[]

[Kernels]
  [diff]
    type = MFEMDiffusionKernel
    variable = u
  []
  [td]
    type = MFEMTimeDerivativeMassKernel
    variable = u
  []
[]

[BCs]
  [left]
    type = MFEMScalarDirichletBC
    variable = u
    boundary = left
    coefficient = 0
  []
  [right]
    type = MFEMScalarDirichletBC
    variable = u
    boundary = right
    coefficient = 1
  []
[]

[Preconditioner]
  [boomeramg]
    type = MFEMHypreBoomerAMG
  []
[]

[Solver]
  type = MFEMHyprePCG
  preconditioner = boomeramg
  l_tol = 1e-8
  l_max_its = 100
[]

[Executioner]
  type = MFEMTransient
  num_steps = 2
  dt = 0.01
[]

[Outputs]
  [ParaViewDataCollection]
    type = MFEMParaViewDataCollection
    file_base = OutputData/sub_cycling_sub
    vtk_format = ASCII
  []
[]

(test/tests/mfem/variables/mfem_variables_from_moose.i)

[Mesh]
  type = MFEMMesh
  file = ../mesh/mug.e
  dim = 3
[]

[Problem]
  type = MFEMProblem
[]

[Variables]
  [scalar_var]
    family = LAGRANGE
    order = FIRST
  []
  [vector_var]
    family = LAGRANGE_VEC
    order = FIRST
  []
[]

[AuxVariables]
  [scalar_auxvar]
    family = MONOMIAL
    order = CONSTANT
  []
  [vector_auxvar]
    family = MONOMIAL_VEC
    order = CONSTANT
  []
[]

[BCs]
  [bottom]
    type = MFEMScalarDirichletBC
    variable = scalar_var
    boundary = '1'
    coefficient = 1.0
  []
  [top]
    type = MFEMScalarDirichletBC
    variable = scalar_var
    boundary = '2'
  []
[]

[Kernels]
  [diff]
    type = MFEMDiffusionKernel
    variable = scalar_var
  []
[]

[Preconditioner]
  [boomeramg]
    type = MFEMHypreBoomerAMG
  []
[]

[Solver]
  type = MFEMHypreGMRES
  preconditioner = boomeramg
  l_tol = 1e-16
  l_max_its = 1000
[]

[Executioner]
  type = MFEMTransient
  device = cpu
  dt = 1.0
  start_time = 0.0
  end_time = 1.0
[]

[Outputs]
  [ParaViewDataCollection]
    type = MFEMParaViewDataCollection
    file_base = OutputData/VariableSetupTest
  []
[]

(test/tests/mfem/multiapps/full_solve_parent.i)

[Problem]
  type = MFEMProblem
  verbose_multiapps = true
[]

[Mesh]
  type = MFEMMesh
  file = ../mesh/square.e
[]

[FESpaces]
  [H1FESpace]
    type = MFEMScalarFESpace
    fec_type = H1
    fec_order = FIRST
  []
[]

[Variables]
  [u]
    type = MFEMVariable
    fespace = H1FESpace
  []
[]

[Kernels]
  [diff]
    type = MFEMDiffusionKernel
    variable = u
  []
  [td]
    type = MFEMTimeDerivativeMassKernel
    variable = u
  []
[]

[BCs]
  [left]
    type = MFEMScalarDirichletBC
    variable = u
    boundary = left
    coefficient = 0
  []
  [right]
    type = MFEMScalarDirichletBC
    variable = u
    boundary = right
    coefficient = 1
  []
[]

[Preconditioner]
  [boomeramg]
    type = MFEMHypreBoomerAMG
      print_level = 0
  []
[]

[Solver]
  type = MFEMHyprePCG
  preconditioner = boomeramg
  l_tol = 1e-8
  l_max_its = 100
  print_level = 0
[]

[Executioner]
  type = MFEMTransient
  device = cpu
  num_steps = 2
  dt = 0.1
[]

[Outputs]
  [ParaViewDataCollection]
    type = MFEMParaViewDataCollection
    file_base = OutputData/full_solve_parent
    vtk_format = ASCII
  []
[]

[MultiApps]
  [full_solve]
    type = FullSolveMultiApp
    app_type = MooseTestApp
    execute_on = timestep_begin
    input_files = full_solve_sub.i
    keep_full_output_history = true
  []
[]

(test/tests/mfem/multiapps/dt_from_parent.i)

[Problem]
  type = MFEMProblem
[]

[Mesh]
  type = MFEMMesh
  file = ../mesh/square.e
[]

[FESpaces]
  [H1FESpace]
    type = MFEMScalarFESpace
    fec_type = H1
    fec_order = FIRST
  []
[]

[Variables]
  [u]
    type = MFEMVariable
    fespace = H1FESpace
  []
[]

[Kernels]
  [diff]
    type = MFEMDiffusionKernel
    variable = u
  []
  [td]
    type = MFEMTimeDerivativeMassKernel
    variable = u
  []
[]

[BCs]
  [left]
    type = MFEMScalarDirichletBC
    variable = u
    boundary = left
    coefficient = 0
  []
  [right]
    type = MFEMScalarDirichletBC
    variable = u
    boundary = right
    coefficient = 1
  []
[]

[Preconditioner]
  [boomeramg]
    type = MFEMHypreBoomerAMG
  []
[]

[Solver]
  type = MFEMHyprePCG
  preconditioner = boomeramg
  l_tol = 1e-8
  l_max_its = 100
[]

[Executioner]
  type = MFEMTransient
  device = cpu
  num_steps = 10
  dt = 0.2
[]

[Outputs]
  [ParaViewDataCollection]
    type = MFEMParaViewDataCollection
    file_base = OutputData/dt_from_parent
    vtk_format = ASCII
  []
[]

[MultiApps]
  [sub_app]
    type = TransientMultiApp
    app_type = MooseTestApp
    input_files = 'dt_from_parent_sub.i'
  []
[]

(test/tests/mfem/multiapps/dt_from_parent_sub.i)

[Problem]
  type = MFEMProblem
[]

[Mesh]
  type = MFEMMesh
  file = ../mesh/square.e
[]

[FESpaces]
  [H1FESpace]
    type = MFEMScalarFESpace
    fec_type = H1
    fec_order = FIRST
  []
[]

[Variables]
  [u]
    type = MFEMVariable
    fespace = H1FESpace
  []
[]

[Kernels]
  [diff]
    type = MFEMDiffusionKernel
    variable = u
  []
  [td]
    type = MFEMTimeDerivativeMassKernel
    variable = u
  []
[]

[BCs]
  [left]
    type = MFEMScalarDirichletBC
    variable = u
    boundary = left
    coefficient = 0
  []
  [right]
    type = MFEMScalarDirichletBC
    variable = u
    boundary = right
    coefficient = 1
  []
[]

[Preconditioner]
  [boomeramg]
    type = MFEMHypreBoomerAMG
  []
[]

[Solver]
  type = MFEMHyprePCG
  preconditioner = boomeramg
  l_tol = 1e-8
  l_max_its = 100
[]

[Executioner]
  type = MFEMTransient
  num_steps = 10
  dt = 1 # This will be constrained by the parent solve
[]

[Outputs]
  [ParaViewDataCollection]
    type = MFEMParaViewDataCollection
    file_base = OutputData/dt_from_parent_sub
    vtk_format = ASCII
  []
[]

(test/tests/mfem/multiapps/full_solve_sub.i)

[Problem]
  type = MFEMProblem
  verbose_multiapps = true
[]

[Mesh]
  type = MFEMMesh
  file = ../mesh/square.e
[]

[FESpaces]
  [H1FESpace]
    type = MFEMScalarFESpace
    fec_type = H1
    fec_order = FIRST
  []
[]

[Variables]
  [u]
    type = MFEMVariable
    fespace = H1FESpace
  []
[]

[Kernels]
  [diff]
    type = MFEMDiffusionKernel
    variable = u
  []
  [td]
    type = MFEMTimeDerivativeMassKernel
    variable = u
  []
[]

[BCs]
  [left]
    type = MFEMScalarDirichletBC
    variable = u
    boundary = left
    coefficient = 0
  []
  [right]
    type = MFEMScalarDirichletBC
    variable = u
    boundary = right
    coefficient = 1
  []
[]

[Preconditioner]
  [boomeramg]
    type = MFEMHypreBoomerAMG
      print_level = 0
  []
[]

[Solver]
  type = MFEMHyprePCG
  preconditioner = boomeramg
  l_tol = 1e-8
  l_max_its = 100
  print_level = 0
[]

[Executioner]
  type = MFEMTransient
  num_steps = 2
  dt = 0.01
[]

[Outputs]
  [ParaViewDataCollection]
    type = MFEMParaViewDataCollection
    file_base = OutputData/full_solve_sub
    vtk_format = ASCII
  []
[]

(test/tests/mfem/kernels/heattransfer.i)

[Mesh]
  type = MFEMMesh
  file = ../mesh/mug.e
  dim = 3
[]

[Problem]
  type = MFEMProblem
[]

[FESpaces]
  [H1FESpace]
    type = MFEMScalarFESpace
    fec_type = H1
    fec_order = FIRST
  []
[]

[Variables]
  [temperature]
    type = MFEMVariable
    fespace = H1FESpace
  []
[]

[AuxVariables]
  inactive = average_temperature
  [average_temperature]
    type = MFEMVariable
    fespace = H1FESpace
  []
[]

[AuxKernels]
  inactive = average_field
  [average_field]
    type = MFEMScalarTimeAverageAux
    variable = average_temperature
    source = temperature
  []
[]

[Kernels]
  [diff]
    type = MFEMDiffusionKernel
    variable = temperature
  []
  [dT_dt]
    type = MFEMTimeDerivativeMassKernel
    variable = temperature
  []
[]

[BCs]
  active = 'bottom top_convective'
  [bottom]
    type = MFEMScalarDirichletBC
    variable = temperature
    boundary = '1'
    coefficient = 1.0
  []
  [top_convective]
    type = MFEMConvectiveHeatFluxBC
    variable = temperature
    boundary = '2'
    T_infinity = .5
    heat_transfer_coefficient = 5
  []
  [top_dirichlet]
    type = MFEMScalarDirichletBC
    variable = temperature
    boundary = '2'
  []
[]

[Preconditioner]
  [boomeramg]
    type = MFEMHypreBoomerAMG
  []
  [jacobi]
    type = MFEMOperatorJacobiSmoother
  []
[]

[Solver]
  type = MFEMHypreGMRES
  preconditioner = boomeramg
  l_tol = 1e-16
  l_max_its = 1000
[]

[Executioner]
  type = MFEMTransient
  device = cpu
  assembly_level = legacy
  dt = 2.0
  start_time = 0.0
  end_time = 6.0
[]

[Outputs]
  [ParaViewDataCollection]
    type = MFEMParaViewDataCollection
    file_base = OutputData/HeatTransfer
    vtk_format = ASCII
  []
[]

(test/tests/mfem/multiapps/sub_cycling_parent.i)

[Problem]
  type = MFEMProblem
  verbose_multiapps = true
[]

[Mesh]
  type = MFEMMesh
  file = ../mesh/square.e
[]

[FESpaces]
  [H1FESpace]
    type = MFEMScalarFESpace
    fec_type = H1
    fec_order = FIRST
  []
[]

[Variables]
  [u]
    type = MFEMVariable
    fespace = H1FESpace
  []
[]

[Kernels]
  [diff]
    type = MFEMDiffusionKernel
    variable = u
  []
  [td]
    type = MFEMTimeDerivativeMassKernel
    variable = u
  []
[]

[BCs]
  [left]
    type = MFEMScalarDirichletBC
    variable = u
    boundary = left
    coefficient = 0
  []
  [right]
    type = MFEMScalarDirichletBC
    variable = u
    boundary = right
    coefficient = 1
  []
[]

[Preconditioner]
  [boomeramg]
    type = MFEMHypreBoomerAMG
  []
[]

[Solver]
  type = MFEMHyprePCG
  preconditioner = boomeramg
  l_tol = 1e-8
  l_max_its = 100
[]

[Executioner]
  type = MFEMTransient
  device = cpu
  num_steps = 2
  dt = 0.1
[]

[Outputs]
  [ParaViewDataCollection]
    type = MFEMParaViewDataCollection
    file_base = OutputData/sub_cycling_parent
    vtk_format = ASCII
  []
[]

[MultiApps]
  [sub]
    type = TransientMultiApp
    app_type = MooseTestApp
    execute_on = timestep_end
    positions = '0 0 0'
    input_files = sub_cycling_sub.i
    sub_cycling = true
  []
[]

(test/tests/mfem/timesteppers/mfem_multiple_timesequences.i)

[Problem]
  type = MFEMProblem
[]

[Mesh]
  type = MFEMMesh
  file = ../mesh/square.e
[]

[FESpaces]
  [H1FESpace]
    type = MFEMScalarFESpace
    fec_type = H1
    fec_order = FIRST
  []
[]

[Variables]
  [u]
    type = MFEMVariable
    fespace = H1FESpace
  []
[]

[Kernels]
  [diff]
    type = MFEMDiffusionKernel
    variable = u
    coefficient = 0.1
  []
  [time]
    type = MFEMTimeDerivativeMassKernel
    variable = u
  []
[]

[BCs]
  [left]
    type = MFEMScalarDirichletBC
    variable = u
    boundary = left
    coefficient = 0
  []
  [right]
    type = MFEMScalarDirichletBC
    variable = u
    boundary = right
    coefficient = 1
  []
[]

[Preconditioner]
  [boomeramg]
    type = MFEMHypreBoomerAMG
  []
[]

[Solver]
  type = MFEMHyprePCG
  preconditioner = boomeramg
  l_tol = 1e-8
  l_max_its = 100
[]

[Executioner]
  type = MFEMTransient
  device = cpu
  end_time = 0.8

  # Use as many different time sequence steppers as we could to test the compositionDT
  [TimeSteppers]
    [ConstDT1]
      type = ConstantDT
      dt = 0.2
    []

    [ConstDT2]
      type = ConstantDT
      dt = 0.1
    []

    [LogConstDT]
      type = LogConstantDT
      log_dt = 0.2
      first_dt = 0.1
    []

    [Timesequence1]
      type = TimeSequenceStepper
      time_sequence  = '0  0.25 0.3 0.5 0.8'
    []

    [Timesequence2]
      type = CSVTimeSequenceStepper
      file_name = timesequence.csv
      column_name = time
    []

    [Timesequence3]
      type = ExodusTimeSequenceStepper
      mesh = timesequence.e
    []
  []
[]

[Postprocessors]
  [timestep]
    type = TimePostprocessor
    execute_on = 'timestep_end'
  []
[]

[Outputs]
  csv = true
  file_base='mfem_multiple_timesequences'
[]

(test/tests/mfem/timesteppers/mfem_multiple_timesteppers.i)

[Problem]
  type = MFEMProblem
[]

[Mesh]
  type = MFEMMesh
  file = ../mesh/square.e
[]

[FESpaces]
  [H1FESpace]
    type = MFEMScalarFESpace
    fec_type = H1
    fec_order = FIRST
  []
[]

[Variables]
  [u]
    type = MFEMVariable
    fespace = H1FESpace
  []
[]

[Kernels]
  [diff]
    type = MFEMDiffusionKernel
    variable = u
    coefficient = 0.1
  []
  [time]
    type = MFEMTimeDerivativeMassKernel
    variable = u
  []
[]

[Functions]
  [dts]
    type = PiecewiseLinear
    x = '0   0.85 2'
    y = '0.2 0.15  0.2'
  []
[]

[BCs]
  [left]
    type = MFEMScalarDirichletBC
    variable = u
    boundary = left
    coefficient = 0
  []
  [right]
    type = MFEMScalarDirichletBC
    variable = u
    boundary = right
    coefficient = 1
  []
[]

[Preconditioner]
  [boomeramg]
    type = MFEMHypreBoomerAMG
  []
[]

[Solver]
  type = MFEMHyprePCG
  preconditioner = boomeramg
  l_tol = 1e-8
  l_max_its = 100
[]

[Executioner]
  type = MFEMTransient
  device = cpu
  end_time = 0.8
  # Use as many different time steppers as we could to test the compositionDT,
  # SolutionTimeAdaptiveDT give slightly different dt per run, set rel_err = 1e-2
  # to ensure the test won't fail due to the small difference in the high-digit.
  [TimeSteppers]
    [ConstDT1]
      type = ConstantDT
      dt = 0.2
    []

    [FunctionDT]
      type = FunctionDT
      function = dts
    []

    [LogConstDT]
      type = LogConstantDT
      log_dt = 0.2
      first_dt = 0.1
    []

    [IterationAdapDT]
      type = IterationAdaptiveDT
      dt = 0.5
    []

    [Timesequence]
      type = TimeSequenceStepper
      time_sequence  = '0  0.25 0.3 0.5 0.8'
    []
  []
[]

[Postprocessors]
  [timestep]
    type = TimePostprocessor
    execute_on = 'timestep_end'
  []
[]

[Outputs]
  csv = true
  file_base='mfem_multiple_timesteppers'
[]

(test/tests/mfem/ics/transient_scalar_ic.i)

[Mesh]
  type = MFEMMesh
  file = ../mesh/cylinder-hex-q2.gen
[]

[Problem]
  type = MFEMProblem
[]

[FESpaces]
  [H1FESpace]
    type = MFEMScalarFESpace
    fec_type = H1
    fec_order = FIRST
  []
  [L2FESpace]
    type = MFEMScalarFESpace
    fec_type = L2
    fec_order = CONSTANT
  []
[]

[Variables]
  [h1_scalar]
    type = MFEMVariable
    fespace = H1FESpace
  []
[]

[AuxVariables]
  [l2_scalar]
    type = MFEMVariable
    fespace = L2FESpace
  []
[]

[Functions]
  [height]
    type = ParsedFunction
    expression = 'z'
  []
[]

[ICs]
  [l2_scalar_ic]
    type = MFEMScalarIC
    variable = l2_scalar
    coefficient = 2.0
  []
  [h1_scalar_ic]
    type = MFEMScalarIC
    variable = h1_scalar
    coefficient = height
  []
[]

[Kernels]
  [h1_laplacian]
    type = MFEMDiffusionKernel
    variable = h1_scalar
    coefficient = 1.0
  []
  [dh1_dt]
    type = MFEMTimeDerivativeMassKernel
    variable = h1_scalar
    coefficient = 1.0
  []
[]

[BCs]
  [bottom]
    type = MFEMScalarDirichletBC
    variable = h1_scalar
    boundary = '1'
    coefficient = height
  []
  [top_dirichlet]
    type = MFEMScalarDirichletBC
    variable = h1_scalar
    boundary = '2'
    coefficient = height
  []
[]

[Preconditioner]
  [boomeramg]
    type = MFEMHypreBoomerAMG
  []
[]

[Solver]
  type = MFEMHypreGMRES
  preconditioner = boomeramg
  l_tol = 1e-8
  l_max_its = 100
[]

[Executioner]
  type = MFEMTransient
  device = cpu
  dt = 2.0
  start_time = 0.0
  end_time = 2.0
[]

[Outputs]
  [ParaViewDataCollection]
    type = MFEMParaViewDataCollection
    file_base = OutputData/TransientScalarIC
    vtk_format = ASCII
  []
[]

Summary
Overview
Example Input File Syntax
Input Parameters
Input Files