wave_speed_estimator.h

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//
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// Copyright (C) 2023 - 2025 by the ryujin authors
//
 
#pragma once
 
#include <compile_time_options.h>
 
#include "hyperbolic_system.h"
 
#include <observer_pointer.h>
#include <simd.h>
 
#include <deal.II/base/point.h>
#include <deal.II/base/tensor.h>
 
namespace ryujin
{
  namespace ScalarConservation
  {
    template <int dim, typename Number = double>
    class WaveSpeedEstimatorView;
 
    template <typename ScalarNumber = double>
    class WaveSpeedEstimator : public dealii::ParameterAcceptor
    {
    public:
 
      template <int dim, typename Number = double>
      using View = WaveSpeedEstimatorView<dim, Number>;
 
 
 
      WaveSpeedEstimator(const HyperbolicSystem &hyperbolic_system,
                         const std::string &subsection = "/WaveSpeedEstimator")
          : ParameterAcceptor(subsection)
          , hyperbolic_system_(&hyperbolic_system)
      {
        use_greedy_wavespeed_ = false;
        add_parameter("use greedy wavespeed",
                      use_greedy_wavespeed_,
                      "Use a greedy wavespeed estimate instead of a guaranteed "
                      "upper bound "
                      "on the maximal wavespeed (for convex fluxes).");
 
        use_averaged_entropy_ = false;
        add_parameter("use averaged entropy",
                      use_averaged_entropy_,
                      "In addition to the wavespeed estimate based on the Roe "
                      "average and "
                      "flux gradients of the left and right state also enforce "
                      "an entropy "
                      "inequality on the averaged Krŭzkov entropy.");
 
        random_entropies_ = 0;
        add_parameter(
            "random entropies",
            random_entropies_,
            "In addition to the wavespeed estimate based on the Roe average "
            "and "
            "flux gradients of the left and right state also enforce an "
            "entropy "
            "inequality on the prescribed number of random Krŭzkov entropies.");
      }
 
 
 
      ACCESSOR_READ_ONLY(use_greedy_wavespeed);
      ACCESSOR_READ_ONLY(use_averaged_entropy);
      ACCESSOR_READ_ONLY(random_entropies);
 
      template <int dim, typename Number>
      auto view() const
      {
        return View<dim, Number>{
            hyperbolic_system_->template view<dim, Number>(), *this};
      }
 
    private:
 
 
      bool use_greedy_wavespeed_;
      bool use_averaged_entropy_;
      unsigned int random_entropies_;
 
 
 
      dealii::ObserverPointer<const HyperbolicSystem> hyperbolic_system_;
 
    };
 
 
    template <int dim, typename Number>
    class WaveSpeedEstimatorView
    {
    public:
 
      using View = HyperbolicSystemView<dim, Number>;
 
      using ScalarNumber = typename View::ScalarNumber;
 
      static constexpr auto problem_dimension = View::problem_dimension;
 
      using state_type = typename View::state_type;
 
      using precomputed_type = typename View::precomputed_type;
 
      using PrecomputedVectorView = typename View::PrecomputedVectorView;
 
 
 
      WaveSpeedEstimatorView(
          const View &view,
          const WaveSpeedEstimator<ScalarNumber> &wave_speed_estimator)
          : view_(view)
          , wave_speed_estimator_(wave_speed_estimator)
      {
      }
 
      Number compute(const Number &u_i,
                     const Number &u_j,
                     const precomputed_type &prec_i,
                     const precomputed_type &prec_j,
                     const dealii::Tensor<1, dim, Number> &n_ij) const;
 
      Number compute(const PrecomputedVectorView &pv,
                     const state_type &U_i,
                     const state_type &U_j,
                     const unsigned int i,
                     const unsigned int *js,
                     const dealii::Tensor<1, dim, Number> &n_ij) const;
 
    private:
 
 
      const View view_;
      const WaveSpeedEstimator<ScalarNumber> &wave_speed_estimator_;
 
    };
  } // namespace ScalarConservation
} // namespace ryujin