mesh_adaptor.h

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//
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// Copyright (C) 2024 - 2026 by the ryujin authors
//
 
#pragma once
 
#include <compile_time_options.h>
 
#include "mpi_ensemble.h"
#include "observer_pointer.h"
#include "offline_data.h"
 
#include <deal.II/base/parameter_acceptor.h>
 
#include <random>
 
namespace ryujin
{
  enum class AdaptationStrategy {
    global_refinement,
 
    random_adaptation,
 
    smoothness_indicators,
  };
 
  enum class MarkingStrategy {
    fixed_threshold,
  };
 
  enum class TimePointSelectionStrategy {
    fixed_time_points,
 
    simulation_cycle,
  };
} // namespace ryujin
 
#ifndef DOXYGEN
DECLARE_ENUM(
    ryujin::AdaptationStrategy,
    LIST({ryujin::AdaptationStrategy::global_refinement, "global refinement"},
         {ryujin::AdaptationStrategy::random_adaptation, "random adaptation"},
         {ryujin::AdaptationStrategy::smoothness_indicators,
          "smoothness indicators"}, ));
 
DECLARE_ENUM(ryujin::MarkingStrategy,
             LIST({ryujin::MarkingStrategy::fixed_threshold,
                   "fixed threshold"}));
 
DECLARE_ENUM(ryujin::TimePointSelectionStrategy,
             LIST({ryujin::TimePointSelectionStrategy::fixed_time_points,
                   "fixed time points"},
                  {ryujin::TimePointSelectionStrategy::simulation_cycle,
                   "simulation cycle"}, ));
#endif
 
namespace ryujin
{
  template <typename Description, int dim, typename Number = double>
  class MeshAdaptor final : public dealii::ParameterAcceptor
  {
  public:
 
    using HyperbolicSystem = typename Description::HyperbolicSystem;
    using ParabolicSystem = typename Description::ParabolicSystem;
 
    using View = typename HyperbolicSystem::template View<dim, Number>;
 
    static constexpr auto problem_dimension = View::problem_dimension;
 
    using StateVector = typename View::StateVector;
    using InitialPrecomputedVector = typename View::InitialPrecomputedVector;
    using ScalarVector = Vectors::ScalarVector<Number>;
 
 
 
    MeshAdaptor(const MPIEnsemble &mpi_ensemble,
                const OfflineData<dim, Number> &offline_data,
                const HyperbolicSystem &hyperbolic_system,
                const ParabolicSystem &parabolic_system,
                const InitialPrecomputedVector &initial_precomputed,
                const ScalarVector &alpha,
                const std::string &subsection = "/MeshAdaptor");
 
    void prepare(const Number t);
 
 
 
    void analyze(const StateVector &state_vector,
                 const Number t,
                 unsigned int cycle);
 
    void mark_cells_for_coarsening_and_refinement(
        dealii::Triangulation<dim> &triangulation) const;
 
    void compute_smoothness_indicators(const StateVector &state_vector) const;
 
 
 
    ACCESSOR_READ_ONLY(need_mesh_adaptation)
 
    
    ACCESSOR_READ_ONLY(indicators);
 
    ACCESSOR_READ_ONLY(smoothness_indicators);
 
  private:
 
 
    AdaptationStrategy adaptation_strategy_;
    std::uint_fast64_t random_adaptation_mersenne_twister_seed_;
 
    MarkingStrategy marking_strategy_;
    double coarsening_threshold_;
    double refinement_threshold_;
    bool absolute_threshold_;
    unsigned int min_refinement_level_;
    unsigned int max_refinement_level_;
 
    TimePointSelectionStrategy time_point_selection_strategy_;
    std::vector<Number> adaptation_time_points_;
    unsigned int adaptation_cycle_interval_;
 
    std::vector<std::string> smoothness_selected_quantities_;
    Number smoothness_local_global_ratio_;
    Number smoothness_min_cutoff_;
    Number smoothness_max_cutoff_;
    unsigned int smoothness_widen_stencil_;
 
 
 
    const MPIEnsemble &mpi_ensemble_;
 
    dealii::ObserverPointer<const OfflineData<dim, Number>> offline_data_;
    dealii::ObserverPointer<const HyperbolicSystem> hyperbolic_system_;
    dealii::ObserverPointer<const ParabolicSystem> parabolic_system_;
 
    const InitialPrecomputedVector &initial_precomputed_;
    const ScalarVector &alpha_;
 
    bool need_mesh_adaptation_;
 
    mutable dealii::Vector<float> indicators_;
 
    /* random adaptation: */
    mutable std::mt19937_64 mersenne_twister_;
 
    /* smoothness indicators: */
    mutable ScalarVector smoothness_indicators_;
 
 
 
    /* random adaptation: */
    void populate_cell_indicators_with_random_values() const;
 
    /* smoothness indicators: */
    void populate_cell_indicators_from_smoothness_indicators() const;
 
  };
 
} // namespace ryujin