time_integrator.h

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//
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// Copyright (C) 2022 - 2026 by the ryujin authors
//
 
#pragma once
 
#include <ryujin/base/compile_time_options.h>
#include <ryujin/base/convenience_macros.h>
#include <ryujin/base/mpi_ensemble.h>
#include <ryujin/base/observer_pointer.h>
#include <ryujin/base/patterns_conversion.h>
#include <ryujin/interface/hyperbolic_module.h>
#include <ryujin/interface/hyperbolic_system.h>
#include <ryujin/interface/parabolic_module.h>
#include <ryujin/interface/parabolic_system.h>
#include <ryujin/interface/time_integrator.h>
 
#include <numbers>
 
namespace ryujin
{
  enum class CFLRecoveryStrategy {
    none,
 
    bang_bang_control,
 
    cruise_control,
  };
 
 
  enum class TimeSteppingScheme {
    ssprk_22,
    ssprk_33,
 
    erk_11,
 
    erk_22,
 
    erk_33,
 
    erk_43,
 
    erk_54,
 
    strang_ssprk_33_cn,
 
    strang_erk_33_cn,
 
    strang_erk_43_cn,
 
    imex_11,
 
    imex_22,
 
    imex_33,
  };
} // namespace ryujin
 
#ifndef DOXYGEN
DECLARE_ENUM(
    ryujin::CFLRecoveryStrategy,
    LIST({ryujin::CFLRecoveryStrategy::none, "none"},
         {ryujin::CFLRecoveryStrategy::bang_bang_control, "bang bang control"},
         {ryujin::CFLRecoveryStrategy::cruise_control, "cruise control"}, ));
 
DECLARE_ENUM(
    ryujin::TimeSteppingScheme,
    LIST({ryujin::TimeSteppingScheme::ssprk_22, "ssprk 22"},
         {ryujin::TimeSteppingScheme::ssprk_33, "ssprk 33"},
         {ryujin::TimeSteppingScheme::erk_11, "erk 11"},
         {ryujin::TimeSteppingScheme::erk_22, "erk 22"},
         {ryujin::TimeSteppingScheme::erk_33, "erk 33"},
         {ryujin::TimeSteppingScheme::erk_43, "erk 43"},
         {ryujin::TimeSteppingScheme::erk_54, "erk 54"},
         {ryujin::TimeSteppingScheme::strang_ssprk_33_cn, "strang ssprk 33 cn"},
         {ryujin::TimeSteppingScheme::strang_erk_33_cn, "strang erk 33 cn"},
         {ryujin::TimeSteppingScheme::strang_erk_43_cn, "strang erk 43 cn"},
         {ryujin::TimeSteppingScheme::imex_11, "imex 11"},
         {ryujin::TimeSteppingScheme::imex_22, "imex 22"},
         {ryujin::TimeSteppingScheme::imex_33, "imex 33"}));
#endif
 
namespace ryujin
{
  template <int dim, typename Number = double>
  class TimeIntegrator final : public Interface::TimeIntegrator<dim, Number>
  {
  public:
 
    TimeIntegrator(
        const MPIEnsemble &mpi_ensemble,
        const Interface::HyperbolicSystem &hyperbolic_system,
        const Interface::ParabolicSystem &parabolic_system,
        const Interface::HyperbolicModule<dim, Number> &hyperbolic_module,
        const Interface::ParabolicModule<dim, Number> &parabolic_module,
        const std::string &subsection = "/TimeIntegrator");
 
    void prepare() override;
 
 
 
    void prepare_state_vector(StateVector<Number> &state_vector,
                              Number t) const override;
 
    Number step(StateVector<Number> &state_vector,
                Number t,
                Number t_final = std::numeric_limits<Number>::max()) override;
 
 
 
    ACCESSOR_READ_ONLY(time_stepping_scheme)
 
  private:
 
 
    Number cfl_min_;
    Number cfl_max_;
 
    CFLRecoveryStrategy cfl_recovery_strategy_;
 
    Number acceptable_tau_max_ratio_;
    Number tau_max_;
 
    TimeSteppingScheme time_stepping_scheme_;
 
 
 
    const MPIEnsemble &mpi_ensemble_;
 
    dealii::ObserverPointer<const Interface::HyperbolicSystem>
        hyperbolic_system_;
    dealii::ObserverPointer<const Interface::ParabolicSystem> parabolic_system_;
    dealii::ObserverPointer<const Interface::HyperbolicModule<dim, Number>>
        hyperbolic_module_;
    dealii::ObserverPointer<const Interface::ParabolicModule<dim, Number>>
        parabolic_module_;
 
    std::vector<StateVector<Number>> temp_;
 
 
 
    Number
    step_ssprk_22(StateVector<Number> &state_vector, Number t, Number tau_max);
 
    Number
    step_ssprk_33(StateVector<Number> &state_vector, Number t, Number tau_max);
 
    Number
    step_erk_11(StateVector<Number> &state_vector, Number t, Number tau_max);
 
    Number
    step_erk_22(StateVector<Number> &state_vector, Number t, Number tau_max);
 
    Number
    step_erk_33(StateVector<Number> &state_vector, Number t, Number tau_max);
 
    Number
    step_erk_43(StateVector<Number> &state_vector, Number t, Number tau_max);
 
    Number
    step_erk_54(StateVector<Number> &state_vector, Number t, Number tau_max);
 
    Number step_strang_ssprk_33_cn(StateVector<Number> &state_vector,
                                   Number t,
                                   Number tau_max);
 
    Number step_strang_erk_33_cn(StateVector<Number> &state_vector,
                                 Number t,
                                 Number tau_max);
 
    Number step_strang_erk_43_cn(StateVector<Number> &state_vector,
                                 Number t,
                                 Number tau_max);
 
    Number
    step_imex_11(StateVector<Number> &state_vector, Number t, Number tau_max);
 
    Number
    step_imex_22(StateVector<Number> &state_vector, Number t, Number tau_max);
 
    Number
    step_imex_33(StateVector<Number> &state_vector, Number t, Number tau_max);
 
  };
 
} // namespace ryujin