Split

Field split based preconditioner for nonlinear solver.

This is an alternative syntax to the FSP. The field split based preconditioner is entirely set up by defining the relevant PETSc options. This syntax offers shorthands for some of the parameters that may be passed to PETSc, such as for splitting between variables, blocks or sidesets.

More information about field split preconditioning may be found in the PETSc manual.

Example input syntax

In this example, a two level field split preconditioning is set up using the Split syntax. A Schur decomposition is used for preconditioning at the top level, and asm preconditioning, with their own sets of PETSc options, is set up for two groups of variables.

[Splits]
  [./nuv]
    splitting = 'v nu'
    splitting_type = schur
    schur_type = full
    schur_pre = Sp
    #petsc_options = '-dm_view'
  [../]
  [./nu]
    vars = 'n u'
    petsc_options = '-ksp_monitor'
    petsc_options_iname = '-ksp_gmres_restart -pc_type -pc_asm_overlap  -sub_pc_type'
    petsc_options_value = '              101      asm               5            lu'
  [../]
  [./v]
    vars = 'v'
    #petsc_options = '-ksp_monitor'
    petsc_options_iname = '-pc_type -ksp_gmres_restart -sub_ksp_type -sub_pc_type -pc_asm_overlap'
    petsc_options_value = 'asm         101   preonly   lu      0'
    #full = true
  [../]
[]

Input Parameters

blocksMesh blocks Split operates on (omitting this implies "all blocks"
C++ Type:std::vector<SubdomainName>
Unit:(no unit assumed)
Controllable:No
Description:Mesh blocks Split operates on (omitting this implies "all blocks"
petsc_optionsPETSc flags for the FieldSplit solver
C++ Type:MultiMooseEnum
Unit:(no unit assumed)
Options:-dm_moose_print_embedding, -dm_view, -ksp_converged_reason, -ksp_gmres_modifiedgramschmidt, -ksp_monitor, -ksp_monitor_snes_lg-snes_ksp_ew, -ksp_snes_ew, -snes_converged_reason, -snes_ksp, -snes_ksp_ew, -snes_linesearch_monitor, -snes_mf, -snes_mf_operator, -snes_monitor, -snes_test_display, -snes_view
Controllable:No
Description:PETSc flags for the FieldSplit solver
petsc_options_inamePETSc option names for the FieldSplit solver
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
Controllable:No
Description:PETSc option names for the FieldSplit solver
petsc_options_valuePETSc option values for the FieldSplit solver
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
Controllable:No
Description:PETSc option values for the FieldSplit solver
schur_preSType of Schur complement preconditioner matrix
Default:S
C++ Type:MooseEnum
Unit:(no unit assumed)
Options:S, Sp, A11
Controllable:No
Description:Type of Schur complement preconditioner matrix
schur_typefullType of Schur complement
Default:full
C++ Type:MooseEnum
Unit:(no unit assumed)
Options:full, upper, lower
Controllable:No
Description:Type of Schur complement
sidesSidesets Split operates on (omitting this implies "no sidesets"
C++ Type:std::vector<BoundaryName>
Unit:(no unit assumed)
Controllable:No
Description:Sidesets Split operates on (omitting this implies "no sidesets"
splittingThe names of the splits (subsystems) in the decomposition of this split
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
Controllable:No
Description:The names of the splits (subsystems) in the decomposition of this split
splitting_typeadditiveSplit decomposition type
Default:additive
C++ Type:MooseEnum
Unit:(no unit assumed)
Options:additive, multiplicative, symmetric_multiplicative, schur
Controllable:No
Description:Split decomposition type
unside_by_var_boundary_nameA map from boundary name to unside by variable, e.g. only unside for a given variable.
C++ Type:std::vector<BoundaryName>
Unit:(no unit assumed)
Controllable:No
Description:A map from boundary name to unside by variable, e.g. only unside for a given variable.
unside_by_var_var_nameA map from boundary name to unside by variable, e.g. only unside for a given variable.
C++ Type:std::vector<NonlinearVariableName>
Unit:(no unit assumed)
Controllable:No
Description:A map from boundary name to unside by variable, e.g. only unside for a given variable.
unsidesSidesets Split excludes (omitting this implies "do not exclude any sidesets"
C++ Type:std::vector<BoundaryName>
Unit:(no unit assumed)
Controllable:No
Description:Sidesets Split excludes (omitting this implies "do not exclude any sidesets"
varsVariables Split operates on (omitting this implies "all variables"
C++ Type:std::vector<NonlinearVariableName>
Unit:(no unit assumed)
Controllable:No
Description:Variables Split operates on (omitting this implies "all variables"

Optional Parameters

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:No
Description:Set the enabled status of the MooseObject.

Advanced Parameters

(moose/modules/phase_field/test/tests/phase_field_crystal/PFCTrad/pfct_newton_split1_asm5.i)

[Mesh]
  type = GeneratedMesh
  dim = 2
  nx = 50
  ny = 50
  xmax = 8
  ymax = 8
[]

[Variables]
  [./n]
    [./InitialCondition]
      type = RandomIC
      min = -1
      max = 4
    [../]
  [../]
  [./u]
    scaling = 1e2
  [../]
  [./v]
    scaling = 1e1
  [../]
[]

[Kernels]
  [./ndot]
    type = TimeDerivative
    variable = n
  [../]
  [./n_bulk]
    type = CHBulkPFCTrad
    variable = n
  [../]
  [./u_term]
    type = MatDiffusion
    variable = n
    v = u
    diffusivity = C2
  [../]
  [./v_term]
    type = MatDiffusion
    variable = n
    v = v
    diffusivity = C4
  [../]
  [./u_rctn]
    type = Reaction
    variable = u
  [../]
  [./u_gradn]
    type = LaplacianSplit
    variable = u
    c = n
  [../]
  [./v_rctn]
    type = Reaction
    variable = v
  [../]
  [./v_gradu]
    type = LaplacianSplit
    variable = v
    c = u
  [../]
[]

[BCs]
  [./Periodic]
    [./all]
      auto_direction = 'x y'
    [../]
  [../]
[]

[Materials]
  [./PFCTrad]
    type = PFCTradMaterial
    order = 4
  [../]
[]

[Preconditioning]
  [./SMP]
    type = SMP
    full = true
  [../]
[]

[Executioner]
  type = Transient
  solve_type = 'NEWTON'

  l_max_its = 100
  l_tol = 1e-04
  nl_rel_tol = 1e-09
  nl_abs_tol = 1e-11

  splitting = 'nuv'
  petsc_options = '-snes_view'

  num_steps = 2
  dt = 0.1
[]

[Splits]
  [./nuv]
    splitting       = 'v nu'
    splitting_type  = schur
    schur_type      = full
    schur_pre       = Sp
    #petsc_options = '-dm_view'
  [../]
  [./nu]
    vars = 'n u'
    petsc_options = '-ksp_monitor'
    petsc_options_iname = '-ksp_gmres_restart -pc_type -pc_asm_overlap  -sub_pc_type'
    petsc_options_value =  '              101      asm               5            lu'
  [../]
  [./v]
    vars = 'v'
    #petsc_options = '-ksp_monitor'
    petsc_options_iname = '-pc_type -ksp_gmres_restart -sub_ksp_type -sub_pc_type -pc_asm_overlap'
    petsc_options_value =  'asm         101   preonly   lu      0'
    #full = true
  [../]
[]

[Outputs]
  execute_on = 'initial timestep_end linear'
  exodus = true
[]

Example input syntax
Input Parameters