block_jacobi_preconditioner.h

/*  ______________________________________________________________________
 *
 *  ExaDG - High-Order Discontinuous Galerkin for the Exa-Scale
 *
 *  Copyright (C) 2021 by the ExaDG authors
 *
 *  This program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program.  If not, see <https://www.gnu.org/licenses/>.
 *  ______________________________________________________________________
 */
 
#ifndef EXADG_SOLVERS_AND_PRECONDITIONERS_PRECONDITIONERS_BLOCK_JACOBI_PRECONDITIONER_H_
#define EXADG_SOLVERS_AND_PRECONDITIONERS_PRECONDITIONERS_BLOCK_JACOBI_PRECONDITIONER_H_
 
// ExaDG
#include <exadg/solvers_and_preconditioners/preconditioners/preconditioner_base.h>
 
namespace ExaDG
{
template<typename Operator>
class BlockJacobiPreconditioner : public PreconditionerBase<typename Operator::value_type>
{
public:
  typedef typename PreconditionerBase<typename Operator::value_type>::VectorType VectorType;
 
  BlockJacobiPreconditioner(Operator const & underlying_operator_in, bool const initialize)
    : underlying_operator(underlying_operator_in)
  {
    // initialize block Jacobi
    underlying_operator.initialize_block_diagonal_preconditioner(initialize);
 
    if(initialize)
      this->update_needed = false;
  }
 
  /*
   *  This function updates the block Jacobi preconditioner.
   *  Make sure that the underlying operator has been updated
   *  when calling this function.
   */
  void
  update() final
  {
    underlying_operator.update_block_diagonal_preconditioner();
 
    this->update_needed = false;
  }
 
  /*
   *  This function applies the block Jacobi preconditioner.
   *  Make sure that the block Jacobi preconditioner has been
   *  updated when calling this function.
   */
  void
  vmult(VectorType & dst, VectorType const & src) const final
  {
    AssertThrow(
      not this->update_needed,
      dealii::ExcMessage(
        "Block Jacobi preconditioner can not be applied because it needs to be updated."));
 
    underlying_operator.apply_inverse_block_diagonal(dst, src);
  }
 
private:
  Operator const & underlying_operator;
};
 
} // namespace ExaDG
 
#endif /* EXADG_SOLVERS_AND_PRECONDITIONERS_PRECONDITIONERS_BLOCK_JACOBI_PRECONDITIONER_H_ */