Terminator

Requests termination of the current solve based on the evaluation of a parsed logical expression of the Postprocessor value(s).

The parsed logical expression is specified with the "expression". More information about parsed expressions may be found on the function parser documentation.

The Terminator can act in two modes, specified by the "fail_mode" :

HARD stop, the default, will terminate the simulation when the conditions are met
SOFT stop, will stop the ongoing solve and let the solver try again using a smaller time step, for transient simulations.

note

To use the Terminator as if it were in a PASS mode, where it stops the simulation and accepts the result, use the HARD fail_mode with the INFO error_level.

The message output by the Terminator when the condition for termination is met is specified using the "error_level" parameter. It may be output as:

an error, forcing a hard failure
a warning, to raise attention to an issue or abnormal solve conditions
an information message, to indicate that while the Terminator is acting on the solve, the conditions met are expected or normal. This can be used to make the Terminator stop the simulation but accept the result.

Example input syntax

In this example, the Terminator is used to fail a time step solve, based on a criterion dt > 20. Once the solve is soft-failed for this time step, the solver tries again by cutting the time step. This happens to make the Terminator parsed criterion pass, so it does not act again on this time step.

[UserObjects]
  [arnold]
    type = Terminator
    expression = 'dt > 20'
    fail_mode = SOFT
    execute_on = TIMESTEP_END
  []
[]

In this example, the Terminator is used to stop a simulation and accept the result once the following criterion is met: dt > 20. Stopping simulation is done with the HARD failure mode, and the solve is considered as converged because the error level is set to info.

[UserObjects]
  [arnold]
    type = Terminator
    expression = 'dt > 20'
    fail_mode = HARD
    error_level = INFO
    message = 'Arnold says this should end'
    execute_on = TIMESTEP_END
  []
[]

Input Parameters

expressionFParser expression to process Postprocessor values into a boolean value. Termination of the simulation occurs when this returns true.
C++ Type:FunctionExpression
Unit:(no unit assumed)
Controllable:No
Description:FParser expression to process Postprocessor values into a boolean value. Termination of the simulation occurs when this returns true.

Required Parameters

error_levelINFOThe error level for the message. A level of ERROR will always lead to a hard termination of the entire simulation.
Default:INFO
C++ Type:MooseEnum
Unit:(no unit assumed)
Options:INFO, WARNING, ERROR, NONE
Controllable:No
Description:The error level for the message. A level of ERROR will always lead to a hard termination of the entire simulation.
execute_onTIMESTEP_ENDThe list of flag(s) indicating when this object should be executed. For a description of each flag, see https://mooseframework.inl.gov/source/interfaces/SetupInterface.html.
Default:TIMESTEP_END
C++ Type:ExecFlagEnum
Unit:(no unit assumed)
Options:NONE, INITIAL, LINEAR, NONLINEAR_CONVERGENCE, NONLINEAR, POSTCHECK, TIMESTEP_END, TIMESTEP_BEGIN, MULTIAPP_FIXED_POINT_END, MULTIAPP_FIXED_POINT_BEGIN, FINAL, CUSTOM
Controllable:No
Description:The list of flag(s) indicating when this object should be executed. For a description of each flag, see https://mooseframework.inl.gov/source/interfaces/SetupInterface.html.
fail_modeHARDAbort entire simulation (HARD), just the current time step (SOFT), or not at all (NONE).
Default:HARD
C++ Type:MooseEnum
Unit:(no unit assumed)
Options:HARD, SOFT, NONE
Controllable:No
Description:Abort entire simulation (HARD), just the current time step (SOFT), or not at all (NONE).
messageAn optional message to be output instead of the default message when the termination condition is triggered
C++ Type:std::string
Unit:(no unit assumed)
Controllable:No
Description:An optional message to be output instead of the default message when the termination condition is triggered
prop_getter_suffixAn optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.
C++ Type:MaterialPropertyName
Unit:(no unit assumed)
Controllable:No
Description:An optional suffix parameter that can be appended to any attempt to retrieve/get material properties. The suffix will be prepended with a '_' character.
use_interpolated_stateFalseFor the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.
Default:False
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:For the old and older state use projected material properties interpolated at the quadrature points. To set up projection use the ProjectedStatefulMaterialStorageAction.

Optional Parameters

allow_duplicate_execution_on_initialFalseIn the case where this UserObject is depended upon by an initial condition, allow it to be executed twice during the initial setup (once before the IC and again after mesh adaptivity (if applicable).
Default:False
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:In the case where this UserObject is depended upon by an initial condition, allow it to be executed twice during the initial setup (once before the IC and again after mesh adaptivity (if applicable).
control_tagsAdds user-defined labels for accessing object parameters via control logic.
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
Controllable:No
Description:Adds user-defined labels for accessing object parameters via control logic.
enableTrueSet the enabled status of the MooseObject.
Default:True
C++ Type:bool
Unit:(no unit assumed)
Controllable:Yes
Description:Set the enabled status of the MooseObject.
execution_order_group0Execution order groups are executed in increasing order (e.g., the lowest number is executed first). Note that negative group numbers may be used to execute groups before the default (0) group. Please refer to the user object documentation for ordering of user object execution within a group.
Default:0
C++ Type:int
Unit:(no unit assumed)
Controllable:No
Description:Execution order groups are executed in increasing order (e.g., the lowest number is executed first). Note that negative group numbers may be used to execute groups before the default (0) group. Please refer to the user object documentation for ordering of user object execution within a group.
force_postauxFalseForces the UserObject to be executed in POSTAUX
Default:False
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Forces the UserObject to be executed in POSTAUX
force_preauxFalseForces the UserObject to be executed in PREAUX
Default:False
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Forces the UserObject to be executed in PREAUX
force_preicFalseForces the UserObject to be executed in PREIC during initial setup
Default:False
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Forces the UserObject to be executed in PREIC during initial setup
use_displaced_meshFalseWhether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.
Default:False
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Whether or not this object should use the displaced mesh for computation. Note that in the case this is true but no displacements are provided in the Mesh block the undisplaced mesh will still be used.

Advanced Parameters

(moose/test/tests/userobjects/Terminator/terminator_soft.i)

###########################################################
# This is a test of the UserObject System. The
# Terminator UserObject executes independently after
# each solve and can terminate the solve early due to
# user-defined criteria. (Type: GeneralUserObject)
#
# @Requirement F6.40
###########################################################

[Mesh]
  type = GeneratedMesh
  dim = 2
  nx = 30
  ny = 6
  xmin = -15.0
  xmax = 15.0
  ymin = -3.0
  ymax = 3.0
  elem_type = QUAD4
[]

[Variables]
  [c]
    order = FIRST
    family = LAGRANGE
    initial_condition = 1
  []
[]

[Postprocessors]
  [dt]
    type = TimestepSize
  []
[]

[UserObjects]
  [arnold]
    type = Terminator
    expression = 'dt > 20'
    fail_mode = SOFT
    execute_on = TIMESTEP_END
  []
[]

[Kernels]
  [cres]
    type = Diffusion
    variable = c
  []

  [time]
    type = TimeDerivative
    variable = c
  []
[]

[BCs]
  [c]
    type = DirichletBC
    variable = c
    boundary = left
    value = 0
  []
[]

[Executioner]
  type = Transient
  dt = 100
  num_steps = 6
  nl_abs_step_tol = 1e-10
[]

[Outputs]
  csv = true
  print_linear_residuals = false
[]

(moose/test/tests/userobjects/Terminator/terminator_pass.i)

[Mesh]
  type = GeneratedMesh
  dim = 2
  nx = 30
  ny = 6
  xmin = -15.0
  xmax = 15.0
  ymin = -3.0
  ymax = 3.0
  elem_type = QUAD4
[]

[Variables]
  [c]
    order = FIRST
    family = LAGRANGE
    initial_condition = 1
  []
[]

[Postprocessors]
  [dt]
    type = TimestepSize
  []
[]

[UserObjects]
  [arnold]
    type = Terminator
    expression = 'dt > 20'
    fail_mode = HARD
    error_level = INFO
    message = 'Arnold says this should end'
    execute_on = TIMESTEP_END
  []
[]

[Kernels]
  [cres]
    type = Diffusion
    variable = c
  []

  [time]
    type = TimeDerivative
    variable = c
  []
[]

[BCs]
  [c]
    type = DirichletBC
    variable = c
    boundary = left
    value = 0
  []
[]

[Executioner]
  type = Transient
  [TimeStepper]
    type = IterationAdaptiveDT
    dt = 4
  []
  nl_abs_step_tol = 1e-10
[]

[Outputs]
  csv = true
  print_linear_residuals = false
[]

Example input syntax
Input Parameters