resultfunction.hh

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// SPDX-FileCopyrightText: 2021-2024 The Ikarus Developers mueller@ibb.uni-stuttgart.de
// SPDX-License-Identifier: LGPL-3.0-or-later
 
#pragma once
 
#include <type_traits>
#include <utility>
 
#include <dune/vtk/function.hh>
#include <dune/vtk/vtkwriter.hh>
 
#include <ikarus/finiteelements/ferequirements.hh>
 
namespace Ikarus {
namespace Impl {
  struct DefaultUserFunction
  {
  };
} // namespace Impl
 
template <typename FE, template <typename, int, int> class RT, typename UserFunction = Impl::DefaultUserFunction>
class ResultFunction : public Dune::VTKFunction<typename FE::GridView>
{
public:
  using FiniteElement          = FE;
  using FERequirementType      = typename FiniteElement::FERequirementType;
  using GridView               = typename FiniteElement::GridView;
  using ctype                  = typename GridView::ctype;
  constexpr static int griddim = GridView::dimension;
  using Entity                 = typename GridView::template Codim<0>::Entity;
 
  double evaluate(int comp, const Entity& e, const Dune::FieldVector<ctype, griddim>& local) const override {
    auto index = gridView_.indexSet().index(e);
    return evaluateComponent(index, local, comp);
  }
 
  [[nodiscard]] int ncomps() const override {
    if constexpr (std::is_same_v<UserFunction, Impl::DefaultUserFunction>) {
      Dune::FieldVector<ctype, griddim> val(0.0);
      auto sigma = fes_->at(0).template calculateAt<RT>(feRequirements_, val).asVec();
      return static_cast<int>(sigma.size());
    } else
      return userFunction_.ncomps();
  }
 
  [[nodiscard]] constexpr std::string name() const override {
    if constexpr (requires { userFunction_.name(); })
      return userFunction_.name();
    else
      return toString<RT>();
  }
 
  ResultFunction(std::vector<FiniteElement>* fes, const FERequirementType& req)
      : gridView_{fes->at(0).localView().globalBasis().gridView()},
        feRequirements_{req},
        fes_{fes},
        userFunction_{UserFunction{}} {}
 
private:
  double evaluateComponent(int eleID, const Dune::FieldVector<ctype, griddim>& local, int comp) const {
    auto result = fes_->at(eleID).template calculateAt<RT>(feRequirements_, local).asVec();
 
    if constexpr (!std::is_same_v<UserFunction, Impl::DefaultUserFunction>)
      return userFunction_(result, comp);
    else
      return result(comp);
  }
 
  GridView gridView_;
  FERequirementType feRequirements_;
  std::vector<FiniteElement>* fes_;
  [[no_unique_address]] std::string name_{};
  UserFunction userFunction_;
};
 
template <template <typename, int, int> class RT, typename UserFunction = Impl::DefaultUserFunction, typename FE>
auto makeResultFunction(std::vector<FE>* fes, const typename FE::FERequirementType& req) {
  return std::make_shared<ResultFunction<FE, RT, UserFunction>>(fes, req);
}
 
template <template <typename, int, int> class RT, typename UserFunction = Impl::DefaultUserFunction, typename FE>
auto makeResultVtkFunction(std::vector<FE>* fes, const typename FE::FERequirementType& req) {
  return Dune::Vtk::Function<typename FE::GridView>(std::make_shared<ResultFunction<FE, RT, UserFunction>>(fes, req));
}
 
} // namespace Ikarus