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 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>
Controllable:No
Description:Mesh blocks Split operates on (omitting this implies "all blocks"
petsc_optionsPETSc flags for the FieldSplit solver
C++ Type:MultiMooseEnum
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>
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>
Controllable:No
Description:PETSc option values for the FieldSplit solver
schur_preSType of Schur complement preconditioner matrix
Default:S
C++ Type:MooseEnum
Options:S, Sp, A11
Controllable:No
Description:Type of Schur complement preconditioner matrix
schur_typefullType of Schur complement
Default:full
C++ Type:MooseEnum
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>
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>
Controllable:No
Description:The names of the splits (subsystems) in the decomposition of this split
splitting_typeadditiveSplit decomposition type
Default:additive
C++ Type:MooseEnum
Options:additive, multiplicative, symmetric_multiplicative, schur
Controllable:No
Description:Split decomposition type
unsidesSidesets Split excludes (omitting this implies "do not exclude any sidesets"
C++ Type:std::vector<BoundaryName>
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>
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>
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
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
[]