parabolic_module.h

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//
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// Copyright (C) 2025 - 2026 by the ryujin authors
//
 
#pragma once
 
#include <ryujin/base/compile_time_options.h>
#include <ryujin/base/mpi_ensemble.h>
#include <ryujin/discretization/offline_data.h>
#include <ryujin/interface/parabolic_module.h>
#include <ryujin/stub/parabolic_system.h>
#include <ryujin/typed/initial_values.h>
 
#include <deal.II/base/parameter_acceptor.h>
 
#include <limits>
 
namespace ryujin
{
  template <typename HyperbolicDescription, int dim, typename Number>
  class StubParabolicModule final
      : public Interface::ParabolicModule<dim, Number>
  {
  public:
 
    using StageVectors =
        typename Interface::ParabolicModule<dim, Number>::StageVectors;
 
    using StageWeights =
        typename Interface::ParabolicModule<dim, Number>::StageWeights;
 
    using HyperbolicSystem = typename HyperbolicDescription::HyperbolicSystem;
    using ParabolicSystem = StubParabolicSystem;
 
    using View = typename HyperbolicSystem::template View<dim, Number>;
 
 
 
    StubParabolicModule(const MPIEnsemble & /*mpi_ensemble*/,
                        const OfflineData<dim, Number> & /*offline_data*/,
                        const HyperbolicSystem & /*hyperbolic_system*/,
                        const ParabolicSystem & /*parabolic_system*/,
                        const InitialValues<HyperbolicDescription, dim, Number>
                            & /*initial_values*/,
                        const std::string &subsection = "StubParabolicModule")
        : Interface::ParabolicModule<dim, Number>(subsection)
    {
    }
 
    void prepare() override
    {
      // do nothing
    }
 
 
 
    void
    reinit_state_vector(StateVector<Number> & /*state_vector*/) const override
    {
      // do nothing
    }
 
    void prepare_state_vector(StateVector<Number> & /*state_vector*/,
                              Number /*t*/) const override
    {
      Assert(false,
             dealii::ExcMessage("The parabolic system is the identity. This "
                                "function should have never been called."));
    }
 
    Number backward_euler_step(
        const StateVector<Number> &old_state_vector,
        StageVectors /*stage_state_vectors*/,
        StageWeights /*stage_weights*/,
        StateVector<Number> &new_state_vector,
        Number /*t*/,
        Number tau,
        Number /*tau_max*/ = std::numeric_limits<Number>::max()) const override
    {
      Assert(false,
             dealii::ExcMessage("The parabolic system is the identity. This "
                                "function should have never been called."));
 
      new_state_vector = old_state_vector;
      return tau;
    }
 
    Number crank_nicolson_step(
        const StateVector<Number> &old_state_vector,
        StateVector<Number> &new_state_vector,
        Number /*t*/,
        Number tau,
        Number /*tau_max*/ = std::numeric_limits<Number>::max()) const override
    {
      Assert(false,
             dealii::ExcMessage("The parabolic system is the identity. This "
                                "function should have never been called."));
 
      new_state_vector = old_state_vector;
      return tau;
    }
 
 
 
    void print_solver_statistics(std::ostream & /*output*/) const override
    {
      // do nothing
    }
 
  };
 
 
  struct StubParabolicDescription {
    using ParabolicSystem = StubParabolicSystem;
 
    template <typename HyperbolicDescription, int dim, typename Number = double>
    using ParabolicModule =
        StubParabolicModule<HyperbolicDescription, dim, Number>;
  };
} // namespace ryujin