implicit_euler.hh

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#pragma once
 
// DiFfRG
#include <DiFfRG/common/math.hh>
#include <DiFfRG/common/types.hh>
#include <DiFfRG/discretization/common/abstract_adaptor.hh>
#include <DiFfRG/discretization/common/abstract_assembler.hh>
#include <DiFfRG/discretization/common/abstract_data.hh>
#include <DiFfRG/discretization/data/output_session.hh>
#include <DiFfRG/timestepping/abstract_timestepper.hh>
#include <DiFfRG/timestepping/default_linear_solver.hh>
 
namespace DiFfRG
{
  template <typename VectorType, typename SparseMatrixType, uint dim,
            template <typename...> typename LinearSolver>
  class TimeStepperImplicitEuler_impl : public AbstractTimestepper<VectorType, SparseMatrixType, dim>
  {
    using Base = AbstractTimestepper<VectorType, SparseMatrixType, dim>;
 
  public:
    using NumberType = typename Base::NumberType;
    using BlockVectorType = typename Base::BlockVectorType;
 
    using Base::assembler, Base::data_out, Base::config, Base::adaptor;
    TimeStepperImplicitEuler_impl(const ConfigTree &config, AbstractAssembler<VectorType, SparseMatrixType, dim> &assembler,
                                  OutputSession_impl<dim, VectorType> &data_out)
        : Base(config, assembler, data_out, /*implicit=*/true, /*explicit=*/false)
    {
    }
    TimeStepperImplicitEuler_impl(const ConfigTree &config, AbstractAssembler<VectorType, SparseMatrixType, dim> &assembler,
                                  OutputSession_impl<dim, VectorType> &data_out, AbstractAdaptor<VectorType> &adaptor)
        : Base(config, assembler, data_out, adaptor, /*implicit=*/true, /*explicit=*/false)
    {
    }
    using Base::output_dt, Base::impl, Base::expl;
 
    virtual void run(AbstractFlowingVariables<NumberType, VectorType> &initial_condition, const double t_start,
                     const double t_stop) override;
  };
 
  // ##############################################################################
  // Application-facing spelling
  // ##############################################################################
  //
  // The class above takes the linear algebra spelled out because it is compiled out of line: the
  // set of valid arguments is closed by the explicit instantiations in src/, and keying it on the
  // assembler would explode that set into one instantiation per model. Applications name the
  // assembler instead and let these aliases project it onto that fixed parameter list.
  //
  // The argument is anything exposing VectorType, SparseMatrixType and dim -- an Assembler, or a
  // Discretization where the assembler type is not a single type (e.g. a test that runs one
  // discretization against several models).
  //
  // The solver defaults to DefaultLinearSolver, which follows the linear algebra: UMFPack when it
  // is serial, a distributed direct solve when it is not. Note that <Assembler> and
  // <Assembler, UMFPack> are *different types* even in a serial build -- see the comment on
  // DefaultLinearSolver -- so both need their own explicit instantiation.
  template <typename Assembler, template <typename...> typename LinearSolver = DefaultLinearSolver>
  using TimeStepperImplicitEuler =
      TimeStepperImplicitEuler_impl<typename Assembler::VectorType, typename Assembler::SparseMatrixType,
                                    Assembler::dim, LinearSolver>;
} // namespace DiFfRG