MooseStaticCondensationPreconditioner.C

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//* This file is part of the MOOSE framework
//* https://mooseframework.inl.gov
//*
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//* https://github.com/idaholab/moose/blob/master/COPYRIGHT
//*
//* Licensed under LGPL 2.1, please see LICENSE for details
//* https://www.gnu.org/licenses/lgpl-2.1.html

#include "MooseStaticCondensationPreconditioner.h"

#include "FEProblem.h"
#include "MooseUtils.h"
#include "NonlinearSystemBase.h"
#include "MooseVariableFieldBase.h"
#include "libmesh/implicit_system.h"
#include "libmesh/static_condensation.h"

registerMooseObjectAliased("MooseApp", MooseStaticCondensationPreconditioner, "StaticCondensation");

InputParameters
MooseStaticCondensationPreconditioner::validParams()
{
  InputParameters params = SingleMatrixPreconditioner::validParams();
  params.addClassDescription("Static condensation preconditioner");
  params.set<bool>("full") = true;
  params.suppressParameter<bool>("full");
  params.addParam<std::vector<NonlinearVariableName>>(
      "dont_condense_vars",
      {},
      "A list of variables for whom to not statically condense their degrees of freedom out of the "
      "system. By default all degrees of freedom on element interiors are condensed out.");
  // Need to make this non-defaulted so that isParamValid doesn't always return true
  params.set<MooseEnum>("mffd_type") = "";
  return params;
}

MooseStaticCondensationPreconditioner::MooseStaticCondensationPreconditioner(
    const InputParameters & params)
  : SingleMatrixPreconditioner(params)
{
  auto check_param = [this](const auto & param_name)
  {
    if (isParamValid(param_name))
      paramError(param_name,
                 "This class prefixes every PETSc option so that it applies to the condensed "
                 "system. Given that, there are multiple issues with setting '",
                 param_name,
                 "': 1) it applies to the nonlinear solver algorithm whereas the prefix this class "
                 "applies makes PETSc options conceptually applicable only to the linear solve of "
                 "the statically condensed system 2) these are singleton MOOSE-wrapped PETSc "
                 "options. Consequently even if having multiple prefixes for a system's nonlinear "
                 "solver options made sense, we don't support it. E.g. if you specify '",
                 param_name,
                 "' in both this object's block and the Executioner block, then there will be a "
                 "logical conflict");
  };
  check_param("mffd_type");
  check_param("solve_type");

  // Now check the solve type set in the Executioner
  if (_fe_problem.solverParams(_nl.number())._type != Moose::ST_PJFNK)
    mooseError(
        "Static condensation preconditioning should use a PJFNK solve type. This is because it "
        "provides a means to compute the action of the Jacobian on vectors, which we otherwise "
        "would not have because when using static condensation, the Jacobian is never formed. Note "
        "that actions of the Jacobian on a vector are necessary for things like: GMRES, printing "
        "of linear residuals, or application of line searches like cubic backtracking. These "
        "particular operations can be avoided by using '-ksp_type preonly', disabling printing of "
        "linear residuals, and using the 'cp' or 'basic' line search.");

  auto * const implicit_sys = dynamic_cast<libMesh::ImplicitSystem *>(&_nl.system());
  if (!implicit_sys)
    mooseError("Static condensation can only be used with implicit systems");
  implicit_sys->create_static_condensation();
  auto & sc = implicit_sys->get_static_condensation();
  std::unordered_set<unsigned int> uncondensed_vars;
  for (auto & nl_var_name : getParam<std::vector<NonlinearVariableName>>("dont_condense_vars"))
    uncondensed_vars.insert(_nl.getVariable(0, nl_var_name).number());
  sc.dont_condense_vars(uncondensed_vars);
}

void
MooseStaticCondensationPreconditioner::initialSetup()
{
  Moose::PetscSupport::storePetscOptions(_fe_problem, "-" + _nl.name() + "_condensed_", *this);
}