cvfe/elementsolution.hh

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// -*- mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*-
// vi: set et ts=4 sw=4 sts=4:
//
// SPDX-FileCopyrightText: Copyright © DuMux Project contributors, see AUTHORS.md in root folder
// SPDX-License-Identifier: GPL-3.0-or-later
//
#ifndef DUMUX_CVFE_ELEMENT_SOLUTION_HH
#define DUMUX_CVFE_ELEMENT_SOLUTION_HH
 
#include <type_traits>
#include <dune/common/reservedvector.hh>
 
#include <dumux/common/typetraits/griddiscretization.hh>
#include <dumux/common/typetraits/localdofs_.hh>
#include <dumux/discretization/method.hh>
#include <dumux/discretization/cvfe/localdof.hh>
 
namespace Dumux {
 
namespace Detail {
 
template<class ElementVariables>
constexpr auto primaryVariablesType()
{
    if constexpr (requires { typename ElementVariables::Variables::PrimaryVariables; })
        return std::type_identity<typename ElementVariables::Variables::PrimaryVariables>{};
    else if constexpr (requires { typename ElementVariables::VolumeVariables::PrimaryVariables; })
        return std::type_identity<typename ElementVariables::VolumeVariables::PrimaryVariables>{};
    else
        return std::type_identity<void>{};
}
 
template<class ElementVariables>
using PrimaryVariables_t = typename decltype(primaryVariablesType<ElementVariables>())::type;
 
} // end namespace Detail

template<class FVElementGeometry, class PV>
class CVFEElementSolution
{
    using GridGeometry = typename FVElementGeometry::GridGeometry;
    using GridView = typename GridGeometry::GridView;
    using Element = typename GridView::template Codim<0>::Entity;
 
    static constexpr int dim = GridView::dimension;
 
    // Maximum number of local element dofs
    static constexpr int maxNumLocalDofs = Detail::LocalDofs::maxNumLocalDofs<FVElementGeometry>();
 
public:
    using PrimaryVariables = PV;

    CVFEElementSolution() = default;

    template<class SolutionVector>
    CVFEElementSolution(const Element& element, const SolutionVector& sol,
                        const GridGeometry& gridGeometry)
    {
        update(element, sol, gridGeometry);
    }

    template<class ElementVariables>
    CVFEElementSolution(const Element& element, const ElementVariables& elemVars,
                        const FVElementGeometry& fvGeometry)
    {
        priVars_.resize(Detail::LocalDofs::numLocalDofs(fvGeometry));
        for (const auto& localDof : localDofs(fvGeometry))
            priVars_[localDof.index()] = elemVars[localDof.index()].priVars();
    }

    template<class SolutionVector>
    void update(const Element& element, const SolutionVector& sol,
                const GridGeometry& gridGeometry)
    {
        // For schemes with multiple DOFs per entity (e.g. PQ3 with 2 DOFs per edge)
        // the formula subIndex + localKey.index() may need an orientation flip for
        // simplex elements (see HybridPQ3GeometryHelper::dofIndex for details).
        // If the grid geometry exposes a flip-aware dofIndex(element, localKey)
        // method, use it; otherwise fall back to the generic formula.
        // As local-global mappings are provided by the grid geometry
        // this logic should maybe become part of the grid geometry.
        const auto& localCoeff = gridGeometry.feCache().get(element.type()).localCoefficients();
        priVars_.resize(localCoeff.size());
        for (int localDofIdx = 0; localDofIdx < localCoeff.size(); ++localDofIdx)
        {
            const auto& localKey = localCoeff.localKey(localDofIdx);
            if constexpr (requires { gridGeometry.dofIndex(element, localKey); })
                priVars_[localDofIdx] = sol[gridGeometry.dofIndex(element, localKey)];
            else
                priVars_[localDofIdx] = sol[
                    gridGeometry.dofMapper().subIndex(
                        element, localKey.subEntity(), localKey.codim()
                    ) + localKey.index()
                ];
        }
    }

    template<class SolutionVector>
    void update(const Element& element, const SolutionVector& sol,
                const FVElementGeometry& fvGeometry)
    {
        priVars_.resize(Detail::LocalDofs::numLocalDofs(fvGeometry));
        for (const auto& localDof : localDofs(fvGeometry))
            priVars_[localDof.index()] = sol[localDof.dofIndex()];
    }

    std::size_t size() const
    { return priVars_.size(); }

    template<typename IndexType>
    const PrimaryVariables& operator [](IndexType i) const
    { return priVars_[i]; }

    template<typename IndexType>
    PrimaryVariables& operator [](IndexType i)
    { return priVars_[i]; }
 
private:
    Dune::ReservedVector<PrimaryVariables, maxNumLocalDofs> priVars_;
};

template<class Element, class SolutionVector, class GridGeometry>
auto elementSolution(const Element& element, const SolutionVector& sol, const GridGeometry& gg)
-> std::enable_if_t<DiscretizationMethods::isCVFE<typename GridGeometry::DiscretizationMethod>,
                    CVFEElementSolution<typename GridGeometry::LocalView,
                                      std::decay_t<decltype(std::declval<SolutionVector>()[0])>>
                    >
{
    using PrimaryVariables = std::decay_t<decltype(std::declval<SolutionVector>()[0])>;
    return CVFEElementSolution<typename GridGeometry::LocalView, PrimaryVariables>(element, sol, gg);
}

template<class Element, class ElementVariables, class FVElementGeometry>
    requires ((requires { typename FVElementGeometry::GridDiscretization; }
               || requires { typename FVElementGeometry::GridGeometry; })
              && DiscretizationMethods::isCVFE<typename GridDiscretization_t<FVElementGeometry>::DiscretizationMethod>
              && !std::is_void_v<Detail::PrimaryVariables_t<ElementVariables>>)
auto elementSolution(const Element& element, const ElementVariables& elemVars, const FVElementGeometry& gg)
-> CVFEElementSolution<FVElementGeometry, Detail::PrimaryVariables_t<ElementVariables>>
{
    using PrimaryVariables = Detail::PrimaryVariables_t<ElementVariables>;
    return CVFEElementSolution<FVElementGeometry, PrimaryVariables>(element, elemVars, gg);
}
 
} // end namespace Dumux
 
#endif