PBP

Physics-based preconditioner (PBP) allows individual physics to have their own preconditioner.

Overview

Physics based preconditioning (PBP) is an advanced concept used to more efficiently solve using JFNK. The idea is to create a preconditioning process that targets each physics individually. In this way you can create a more effective preconditioner, while also maintaining efficiency. This object allows you to dial up a preconditioning matrix and the operations to be done on the different blocks of that matrix on the fly from the input file.

The PBP works by partially inverting a preconditioning matrix (usually an approximation of the true Jacobian) by partially inverting each block row in a Block-Gauss-Seidel way.

var element = document.getElementById("moose-equation-4700e07a-73a7-4425-806d-0b5b63470956");katex.render("\\boldsymbol{R}(u,v) = \\begin{bmatrix} \\boldsymbol{R}_u \\\\ \\boldsymbol{R}_v \\end{bmatrix}", element, {displayMode:true,throwOnError:false});

var element = document.getElementById("moose-equation-933a2725-568b-42ee-a2d4-a538ab414bf4");katex.render("\\boldsymbol{M} \\equiv \\begin{bmatrix} (\\boldsymbol{R}_u)_u & \\boldsymbol{0} \\\\ (\\boldsymbol{R}_v)_u & (\\boldsymbol{R}_v)_v \\end{bmatrix} \\approx \\boldsymbol{R}'", element, {displayMode:true,throwOnError:false});

var element = document.getElementById("moose-equation-1c87c915-864e-424f-87d0-64b70792f754");katex.render("\\boldsymbol{M} \\boldsymbol{q} = \\boldsymbol{p} \\quad \\Rightarrow \\quad \\left\\{ \\begin{array}{rcl} (\\boldsymbol{R}_u)_u \\boldsymbol{q}_u &=& \\boldsymbol{p}_u \\\\[6pt] (\\boldsymbol{R}_v)_v \\boldsymbol{q}_v &=& \\boldsymbol{p}_v - (\\boldsymbol{R}_v)_u \\boldsymbol{q}_u \\end{array} \\right.", element, {displayMode:true,throwOnError:false});

Example Input File Syntax

Set up a PBP object for a two variable system (consisting of variables "u" and "v"). Use ILU for the "u" block and AMG for "v". Use the lower diagonal (v,u) block. When using type = PBP, MOOSE will set solve_type = JFNK automatically.


[Preconditioning]
  active = 'myPBP'

  [myPBP]
    type = PBP
    solve_order = 'u v'
    preconditioner  = 'ILU AMG'
    off_diag_row    = 'v'
    off_diag_column = 'u'
  []
[]

Input Parameters

preconditionerTODO: docstring
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
Controllable:No
Description:TODO: docstring
solve_orderThe order the block rows will be solved in. Put the name of variables here to stand for solving that variable's block row. A variable may appear more than once (to create cylces if you like).
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
Controllable:No
Description:The order the block rows will be solved in. Put the name of variables here to stand for solving that variable's block row. A variable may appear more than once (to create cylces if you like).

Required Parameters

fullFalseSet to true if you want the full set of couplings between variables simply for convenience so you don't have to set every off_diag_row and off_diag_column combination.
Default:False
C++ Type:bool
Unit:(no unit assumed)
Controllable:No
Description:Set to true if you want the full set of couplings between variables simply for convenience so you don't have to set every off_diag_row and off_diag_column combination.
ksp_normunpreconditionedSets the norm that is used for convergence testing
Default:unpreconditioned
C++ Type:MooseEnum
Unit:(no unit assumed)
Options:none, preconditioned, unpreconditioned, natural, default
Controllable:No
Description:Sets the norm that is used for convergence testing
nl_sysThe nonlinear system whose linearization this preconditioner should be applied to.
C++ Type:NonlinearSystemName
Unit:(no unit assumed)
Controllable:No
Description:The nonlinear system whose linearization this preconditioner should be applied to.
off_diag_columnThe variable names for the off-diagonal columns you want to add into the matrix; they will be associated with an off-diagonal row from the same position in off_diag_row.
C++ Type:std::vector<NonlinearVariableName>
Unit:(no unit assumed)
Controllable:No
Description:The variable names for the off-diagonal columns you want to add into the matrix; they will be associated with an off-diagonal row from the same position in off_diag_row.
off_diag_rowThe variable names for the off-diagonal rows you want to add into the matrix; they will be associated with an off-diagonal column from the same position in off_diag_column.
C++ Type:std::vector<NonlinearVariableName>
Unit:(no unit assumed)
Controllable:No
Description:The variable names for the off-diagonal rows you want to add into the matrix; they will be associated with an off-diagonal column from the same position in off_diag_column.
pc_sidedefaultPreconditioning side
Default:default
C++ Type:MooseEnum
Unit:(no unit assumed)
Options:left, right, symmetric, default
Controllable:No
Description:Preconditioning side

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

mffd_typewpSpecifies the finite differencing type for Jacobian-free solve types. Note that the default is wp (for Walker and Pernice).
Default:wp
C++ Type:MooseEnum
Unit:(no unit assumed)
Options:wp, ds
Controllable:No
Description:Specifies the finite differencing type for Jacobian-free solve types. Note that the default is wp (for Walker and Pernice).
petsc_optionsSingleton PETSc options
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:Singleton PETSc options
petsc_options_inameNames of PETSc name/value pairs
C++ Type:MultiMooseEnum
Unit:(no unit assumed)
Options:-ksp_atol, -ksp_gmres_restart, -ksp_max_it, -ksp_pc_side, -ksp_rtol, -ksp_type, -mat_fd_coloring_err, -mat_fd_type, -mat_mffd_type, -pc_asm_overlap, -pc_factor_levels, -pc_factor_mat_ordering_type, -pc_hypre_boomeramg_grid_sweeps_all, -pc_hypre_boomeramg_max_iter, -pc_hypre_boomeramg_strong_threshold, -pc_hypre_type, -pc_type, -snes_atol, -snes_linesearch_type, -snes_ls, -snes_max_it, -snes_rtol, -snes_divergence_tolerance, -snes_type, -sub_ksp_type, -sub_pc_type
Controllable:No
Description:Names of PETSc name/value pairs
petsc_options_valueValues of PETSc name/value pairs (must correspond with "petsc_options_iname"
C++ Type:std::vector<std::string>
Unit:(no unit assumed)
Controllable:No
Description:Values of PETSc name/value pairs (must correspond with "petsc_options_iname"
solve_typePJFNK: Preconditioned Jacobian-Free Newton Krylov JFNK: Jacobian-Free Newton Krylov NEWTON: Full Newton Solve FD: Use finite differences to compute Jacobian LINEAR: Solving a linear problem
C++ Type:MooseEnum
Unit:(no unit assumed)
Options:PJFNK, JFNK, NEWTON, FD, LINEAR
Controllable:No
Description:PJFNK: Preconditioned Jacobian-Free Newton Krylov JFNK: Jacobian-Free Newton Krylov NEWTON: Full Newton Solve FD: Use finite differences to compute Jacobian LINEAR: Solving a linear problem

Petsc Parameters

Overview
Example Input File Syntax
Input Parameters