discretization/cellcentered/mpfa/elementfluxvariablescache.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-FileCopyrightInfo: Copyright © DuMux Project contributors, see AUTHORS.md in root folder
// SPDX-License-Identifier: GPL-3.0-or-later
//
#ifndef DUMUX_DISCRETIZATION_CCMPFA_ELEMENT_FLUXVARSCACHE_HH
#define DUMUX_DISCRETIZATION_CCMPFA_ELEMENT_FLUXVARSCACHE_HH
 
#include <algorithm>
#include <cassert>
#include <type_traits>
#include <vector>
#include <utility>
 
#include <dune/common/exceptions.hh>
 
namespace Dumux {
 
template<class PrimaryIV, class PrimaryIVDataHandle,
         class SecondaryIV, class SecondaryIVDataHandle>
struct InteractionVolumeDataStorage
{
    std::vector<PrimaryIV> primaryInteractionVolumes;
    std::vector<SecondaryIV> secondaryInteractionVolumes;
 
    std::vector<PrimaryIVDataHandle> primaryDataHandles;
    std::vector<SecondaryIVDataHandle> secondaryDataHandles;
};
 
template<class GFVC, bool cachingEnabled>
class CCMpfaElementFluxVariablesCache;
 
template<class GFVC>
class CCMpfaElementFluxVariablesCache<GFVC, true>
{
public:
    using PrimaryInteractionVolume = typename GFVC::PrimaryInteractionVolume;
    using SecondaryInteractionVolume = typename GFVC::SecondaryInteractionVolume;
 
    using PrimaryIvDataHandle = typename GFVC::PrimaryIvDataHandle;
    using SecondaryIvDataHandle = typename GFVC::SecondaryIvDataHandle;
 
    using FluxVariablesCache = typename GFVC::FluxVariablesCache;
 
    static constexpr bool cachingEnabled = true;
 
    using GridFluxVariablesCache = GFVC;
 
private:
    using FluxVariablesCacheFiller = typename GFVC::Traits::FluxVariablesCacheFiller;
 
    class BoundaryCacheData
    {
        // allow the element flux variables class access to private members
        friend CCMpfaElementFluxVariablesCache<GFVC, true>;
 
    public:
        template<class SubControlVolumeFace>
        const FluxVariablesCache& operator [](const SubControlVolumeFace& scvf) const
        { return fluxVarCaches_[getLocalIdx_(scvf.index())]; }
 
        template<class SubControlVolumeFace>
        FluxVariablesCache& operator [](const SubControlVolumeFace& scvf)
        { return fluxVarCaches_[getLocalIdx_(scvf.index())]; }
 
        void clear()
        {
            fluxVarCaches_.clear();
            cacheScvfIndices_.clear();
            ivDataStorage_.primaryInteractionVolumes.clear();
            ivDataStorage_.secondaryInteractionVolumes.clear();
            ivDataStorage_.primaryDataHandles.clear();
            ivDataStorage_.secondaryDataHandles.clear();
        }
 
    private:
        int getLocalIdx_(const int scvfIdx) const
        {
            auto it = std::find(cacheScvfIndices_.begin(), cacheScvfIndices_.end(), scvfIdx);
            assert(it != cacheScvfIndices_.end() && "Could not find the local idx for the given scvf idx!");
            return std::distance(cacheScvfIndices_.begin(), it);
        }
 
        std::vector<std::size_t> cacheScvfIndices_;
        std::vector<FluxVariablesCache> fluxVarCaches_;
 
        // stored boundary interaction volumes and handles
        using IVDataStorage = InteractionVolumeDataStorage<PrimaryInteractionVolume,
                                                           PrimaryIvDataHandle,
                                                           SecondaryInteractionVolume,
                                                           SecondaryIvDataHandle>;
        IVDataStorage ivDataStorage_;
    };
 
public:
    CCMpfaElementFluxVariablesCache(const GridFluxVariablesCache& global)
    : gridFluxVarsCachePtr_(&global)
    {}
 
    template<class FVElementGeometry, class ElementVolumeVariables>
    CCMpfaElementFluxVariablesCache bindElement(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
                                                const FVElementGeometry& fvGeometry,
                                                const ElementVolumeVariables& elemVolVars) &&
    {
        this->bindElement_(element, fvGeometry, elemVolVars);
        return std::move(*this);
    }
 
    template<class FVElementGeometry, class ElementVolumeVariables>
    void bindElement(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
                     const FVElementGeometry& fvGeometry,
                     const ElementVolumeVariables& elemVolVars) &
    { this->bindElement_(element, fvGeometry, elemVolVars); }
 
    template<class FVElementGeometry, class ElementVolumeVariables>
    CCMpfaElementFluxVariablesCache bind(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
                                         const FVElementGeometry& fvGeometry,
                                         const ElementVolumeVariables& elemVolVars) &&
    {
        this->bind_(element, fvGeometry, elemVolVars);
        return std::move(*this);
    }
 
    template<class FVElementGeometry, class ElementVolumeVariables>
    void bind(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
              const FVElementGeometry& fvGeometry,
              const ElementVolumeVariables& elemVolVars) &
    { this->bind_(element, fvGeometry, elemVolVars); }
 
    template<class FVElementGeometry, class ElementVolumeVariables>
    CCMpfaElementFluxVariablesCache bindScvf(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
                                             const FVElementGeometry& fvGeometry,
                                             const ElementVolumeVariables& elemVolVars,
                                             const typename FVElementGeometry::SubControlVolumeFace& scvf) &&
    {
        this->bindScvf_(element, fvGeometry, elemVolVars, scvf);
        return std::move(*this);
    }
 
    template<class FVElementGeometry, class ElementVolumeVariables>
    void bindScvf(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
                  const FVElementGeometry& fvGeometry,
                  const ElementVolumeVariables& elemVolVars,
                  const typename FVElementGeometry::SubControlVolumeFace& scvf) &
    { this->bindScvf_(element, fvGeometry, elemVolVars, scvf); }
 
    template<class FVElementGeometry, class ElementVolumeVariables>
    void update(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
                const FVElementGeometry& fvGeometry,
                const ElementVolumeVariables& elemVolVars)
    {
        // Update only if the filler puts solution-dependent stuff into the caches
        if (FluxVariablesCacheFiller::isSolDependent)
        {
            // helper class to fill flux variables caches
            FluxVariablesCacheFiller filler(gridFluxVarsCachePtr_->problem());
 
            // first, set all the caches to "outdated"
            for (auto& cache : boundaryCacheData_.fluxVarCaches_)
                cache.setUpdateStatus(false);
 
            // go through the caches maybe update them
            for (auto scvfIdx : boundaryCacheData_.cacheScvfIndices_)
            {
                const auto& scvf = fvGeometry.scvf(scvfIdx);
                auto& scvfCache = boundaryCacheData_[scvf];
                if (!scvfCache.isUpdated())
                    filler.fill(boundaryCacheData_, scvfCache, boundaryCacheData_.ivDataStorage_,
                                fvGeometry, elemVolVars, scvf);
            }
        }
    }
 
    template<class SubControlVolumeFace>
    const FluxVariablesCache& operator [](const SubControlVolumeFace& scvf) const
    { return !isEmbeddedInBoundaryIV_(scvf) ? (*gridFluxVarsCachePtr_)[scvf] : boundaryCacheData_[scvf]; }
 
    template<class SubControlVolumeFace>
    const PrimaryInteractionVolume& primaryInteractionVolume(const SubControlVolumeFace& scvf) const
    {
        return isEmbeddedInBoundaryIV_(scvf)
               ? boundaryCacheData_.ivDataStorage_.primaryInteractionVolumes[ (*this)[scvf].ivIndexInContainer() ]
               : gridFluxVarsCachePtr_->primaryInteractionVolume(scvf);
    }
 
    template<class SubControlVolumeFace>
    const PrimaryIvDataHandle& primaryDataHandle(const SubControlVolumeFace& scvf) const
    {
        return isEmbeddedInBoundaryIV_(scvf)
               ? boundaryCacheData_.ivDataStorage_.primaryDataHandles[ (*this)[scvf].ivIndexInContainer() ]
               : gridFluxVarsCachePtr_->primaryDataHandle(scvf);
    }
 
    template<class SubControlVolumeFace>
    const SecondaryInteractionVolume& secondaryInteractionVolume(const SubControlVolumeFace& scvf) const
    {
        return isEmbeddedInBoundaryIV_(scvf)
               ? boundaryCacheData_.ivDataStorage_.secondaryInteractionVolumes[ (*this)[scvf].ivIndexInContainer() ]
               : gridFluxVarsCachePtr_->secondaryInteractionVolume(scvf);
    }
 
    template<class SubControlVolumeFace>
    const SecondaryIvDataHandle& secondaryDataHandle(const SubControlVolumeFace& scvf) const
    {
        return isEmbeddedInBoundaryIV_(scvf)
               ? boundaryCacheData_.ivDataStorage_.secondaryDataHandles[ (*this)[scvf].ivIndexInContainer() ]
               : gridFluxVarsCachePtr_->secondaryDataHandle(scvf);
    }
 
    const GridFluxVariablesCache& gridFluxVarsCache() const
    {  return *gridFluxVarsCachePtr_; }
 
private:
 
 
    template<class FVElementGeometry, class ElementVolumeVariables>
    void bindElement_(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
                      const FVElementGeometry& fvGeometry,
                      const ElementVolumeVariables& elemVolVars)
    { DUNE_THROW(Dune::NotImplemented, "Local element binding of the flux variables cache in mpfa schemes"); }
 
    template<class FVElementGeometry, class ElementVolumeVariables>
    void bind_(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
               const FVElementGeometry& fvGeometry,
               const ElementVolumeVariables& elemVolVars)
    {
        boundaryCacheData_.clear();
 
        // find out how much memory needs to be reserved
        std::size_t numPrimaryIv;   numPrimaryIv = 0;
        std::size_t numSecondaryIv; numSecondaryIv = 0;
        std::size_t numCaches;      numCaches = 0;
 
        const auto& gridGeometry = fvGeometry.gridGeometry();
        const auto& gridIvIndexSets = gridGeometry.gridInteractionVolumeIndexSets();
 
        // lambda to check if a scvf was handled already
        auto scvfHandled = [&] (auto idx)
        {
            return std::find(boundaryCacheData_.cacheScvfIndices_.begin(),
                             boundaryCacheData_.cacheScvfIndices_.end(),
                             idx) != boundaryCacheData_.cacheScvfIndices_.end();
        };
 
        // lambda to increase counters for a given scvf
        auto handleScvf = [&] (const auto& scvf, const auto& indexSet, bool isSecondary)
        {
            const auto& scvfIndices = indexSet.gridScvfIndices();
            if ( indexSet.nodalIndexSet().numBoundaryScvfs() > 0
                 && !std::any_of(scvfIndices.begin(), scvfIndices.end(), scvfHandled) )
            {
                boundaryCacheData_.cacheScvfIndices_.insert(boundaryCacheData_.cacheScvfIndices_.end(),
                                                            scvfIndices.begin(),
                                                            scvfIndices.end());
                numCaches += scvfIndices.size();
                if (isSecondary) numSecondaryIv++;
                else numPrimaryIv++;
            }
        };
 
        // search for ivs at boundary vertices
        for (const auto& scvf : scvfs(fvGeometry))
            gridGeometry.vertexUsesSecondaryInteractionVolume(scvf.vertexIndex()) ?
                    handleScvf(scvf, gridIvIndexSets.secondaryIndexSet(scvf), true) :
                    handleScvf(scvf, gridIvIndexSets.primaryIndexSet(scvf),  false) ;
 
        // skip the rest if there are no boundary caches to be created
        if (numCaches > 0)
        {
            const auto& assemblyMapI = gridGeometry.connectivityMap()[gridGeometry.elementMapper().index(element)];
 
            for (const auto& dataJ : assemblyMapI)
            {
                for (const auto& scvfJIdx : dataJ.scvfsJ)
                {
                    const auto& scvfJ = fvGeometry.scvf(scvfJIdx);
                    if (gridGeometry.vertexUsesSecondaryInteractionVolume(scvfJ.vertexIndex()))
                        handleScvf(scvfJ, gridIvIndexSets.secondaryIndexSet(scvfJ), true);
                    else
                        handleScvf(scvfJ, gridIvIndexSets.primaryIndexSet(scvfJ), false);
                }
            }
 
            // now prepare the caches of all scvfs that have been found to be handled
            boundaryCacheData_.ivDataStorage_.primaryInteractionVolumes.reserve(numPrimaryIv);
            boundaryCacheData_.ivDataStorage_.secondaryInteractionVolumes.reserve(numSecondaryIv);
            boundaryCacheData_.ivDataStorage_.primaryDataHandles.reserve(numPrimaryIv);
            boundaryCacheData_.ivDataStorage_.secondaryDataHandles.reserve(numSecondaryIv);
 
            boundaryCacheData_.fluxVarCaches_.resize(numCaches);
            for (auto& cache : boundaryCacheData_.fluxVarCaches_)
                cache.setUpdateStatus(false);
 
            FluxVariablesCacheFiller filler(gridFluxVarsCachePtr_->problem());
            for (auto scvfIdx : boundaryCacheData_.cacheScvfIndices_)
            {
                const auto& scvf = fvGeometry.scvf(scvfIdx);
                auto& cache = boundaryCacheData_[scvf];
                if (!cache.isUpdated())
                    filler.fill(boundaryCacheData_, cache, boundaryCacheData_.ivDataStorage_,
                                fvGeometry, elemVolVars, scvf, /*forceUpdate*/true);
            }
        }
    }
 
    template<class FVElementGeometry, class ElementVolumeVariables>
    void bindScvf_(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
                   const FVElementGeometry& fvGeometry,
                   const ElementVolumeVariables& elemVolVars,
                   const typename FVElementGeometry::SubControlVolumeFace& scvf)
    { DUNE_THROW(Dune::NotImplemented, "Scvf-local binding of the flux variables cache in mpfa schemes"); }
 
    template<class SubControlVolumeFace>
    bool isEmbeddedInBoundaryIV_(const SubControlVolumeFace& scvf) const
    {
        const auto& gridGeometry = gridFluxVarsCachePtr_->problem().gridGeometry();
        const auto& gridIvIndexSets = gridGeometry.gridInteractionVolumeIndexSets();
        if (gridGeometry.vertexUsesSecondaryInteractionVolume(scvf.vertexIndex()))
            return gridIvIndexSets.secondaryIndexSet(scvf).nodalIndexSet().numBoundaryScvfs() > 0;
        else
            return gridIvIndexSets.primaryIndexSet(scvf).nodalIndexSet().numBoundaryScvfs() > 0;
    }
 
    const GridFluxVariablesCache* gridFluxVarsCachePtr_;
 
    // we store those caches that touch the boundary locally here
    // for the case that the boundary conditions change, which would
    // leave the grid-wide cache outdated.
    BoundaryCacheData boundaryCacheData_;
};
 
template<class GFVC>
class CCMpfaElementFluxVariablesCache<GFVC, false>
{
    using FluxVariablesCacheFiller = typename GFVC::Traits::FluxVariablesCacheFiller;
 
public:
    using PrimaryInteractionVolume = typename GFVC::PrimaryInteractionVolume;
    using SecondaryInteractionVolume = typename GFVC::SecondaryInteractionVolume;
 
    using PrimaryIvDataHandle = typename GFVC::PrimaryIvDataHandle;
    using SecondaryIvDataHandle = typename GFVC::SecondaryIvDataHandle;
 
    using FluxVariablesCache = typename GFVC::FluxVariablesCache;
 
 
    static constexpr bool cachingEnabled = false;
 
    using GridFluxVariablesCache = GFVC;
 
    CCMpfaElementFluxVariablesCache(const GridFluxVariablesCache& global)
    : gridFluxVarsCachePtr_(&global) {}
 
    template<class FVElementGeometry, class ElementVolumeVariables>
    void bindElement(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
                     const FVElementGeometry& fvGeometry,
                     const ElementVolumeVariables& elemVolVars) &
    {
        // For mpfa schemes we will have to prepare the caches of all scvfs that are
        // embedded in the interaction volumes in which the element-local scvfs are embedded
        DUNE_THROW(Dune::NotImplemented, "Local element binding of the flux variables cache in mpfa schemes");
    }
 
    template<class FVElementGeometry, class ElementVolumeVariables>
    CCMpfaElementFluxVariablesCache bindElement(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
                                                const FVElementGeometry& fvGeometry,
                                                const ElementVolumeVariables& elemVolVars) &&
    {
        this->bindElement(element, fvGeometry, elemVolVars);
        return std::move(*this);
    }
 
    template<class FVElementGeometry, class ElementVolumeVariables>
    void bind(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
              const FVElementGeometry& fvGeometry,
              const ElementVolumeVariables& elemVolVars) &
    {
        clear_();
 
        // some references for convenience
        const auto& problem = gridFluxVarsCache().problem();
        const auto& gridGeometry = fvGeometry.gridGeometry();
 
        // the assembly map of the given element
        const auto& assemblyMapI = gridGeometry.connectivityMap()[gridGeometry.elementMapper().index(element)];
 
        // reserve memory for scvf index container
        unsigned int numNeighborScvfs = 0;
        for (const auto& dataJ : assemblyMapI)
            numNeighborScvfs += dataJ.scvfsJ.size();
        globalScvfIndices_.resize(fvGeometry.numScvf() + numNeighborScvfs);
 
        // set the scvf indices in scvf index container
        unsigned int i = 0;
        for (const auto& scvf : scvfs(fvGeometry))
            globalScvfIndices_[i++] = scvf.index();
        for (const auto& dataJ : assemblyMapI)
            for (auto scvfIdx : dataJ.scvfsJ)
                globalScvfIndices_[i++] = scvfIdx;
 
        // Reserve memory (over-) estimate for interaction volumes and corresponding data.
        // The overestimate doesn't hurt as we are not in a memory-limited configuration.
        // We need to avoid reallocation because in the caches we store pointers to the data handles.
        // Default -> each facet has two neighbors (local adaption) and all scvfs belongs to different ivs.
        // If you want to use higher local differences change the parameter below.
        constexpr auto numIvEstimate = FVElementGeometry::maxNumElementScvfs
                                       * GridFluxVariablesCache::Traits::maxLocalElementLevelDifference();
        ivDataStorage_.primaryInteractionVolumes.reserve(numIvEstimate);
        ivDataStorage_.secondaryInteractionVolumes.reserve(numIvEstimate);
        ivDataStorage_.primaryDataHandles.reserve(numIvEstimate);
        ivDataStorage_.secondaryDataHandles.reserve(numIvEstimate);
 
        // helper class to fill flux variables caches
        FluxVariablesCacheFiller filler(problem);
 
        // resize the cache container
        fluxVarsCache_.resize(globalScvfIndices_.size());
 
        // go through the caches and fill them
        i = 0;
        for (const auto& scvf : scvfs(fvGeometry))
        {
            auto& scvfCache = fluxVarsCache_[i++];
            if (!scvfCache.isUpdated())
                filler.fill(*this, scvfCache, ivDataStorage_, fvGeometry, elemVolVars, scvf, true);
        }
 
        for (const auto& dataJ : assemblyMapI)
        {
            for (const auto scvfIdx : dataJ.scvfsJ)
            {
                auto& scvfCache = fluxVarsCache_[i++];
                if (!scvfCache.isUpdated())
                    filler.fill(*this, scvfCache, ivDataStorage_, fvGeometry, elemVolVars, fvGeometry.scvf(scvfIdx), true);
            }
        }
    }
 
    template<class FVElementGeometry, class ElementVolumeVariables>
    CCMpfaElementFluxVariablesCache bind(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
                                         const FVElementGeometry& fvGeometry,
                                         const ElementVolumeVariables& elemVolVars) &&
    {
        this->bind(element, fvGeometry, elemVolVars);
        return std::move(*this);
    }
 
    template<class FVElementGeometry, class ElementVolumeVariables>
    void bindScvf(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
                  const FVElementGeometry& fvGeometry,
                  const ElementVolumeVariables& elemVolVars,
                  const typename FVElementGeometry::SubControlVolumeFace& scvf) &
    {
        // For mpfa schemes we will have to prepare the caches of all
        // scvfs that are embedded in the interaction volumes this scvf is embedded
        DUNE_THROW(Dune::NotImplemented, "Scvf-local binding of the flux variables cache in mpfa schemes");
    }
 
    template<class FVElementGeometry, class ElementVolumeVariables>
    CCMpfaElementFluxVariablesCache bindScvf(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
                                             const FVElementGeometry& fvGeometry,
                                             const ElementVolumeVariables& elemVolVars,
                                             const typename FVElementGeometry::SubControlVolumeFace& scvf) &&
    {
        this->bindScvf(element, fvGeometry, elemVolVars, scvf);
        return std::move(*this);
    }
 
    template<class FVElementGeometry, class ElementVolumeVariables>
    void update(const typename FVElementGeometry::GridGeometry::GridView::template Codim<0>::Entity& element,
                const FVElementGeometry& fvGeometry,
                const ElementVolumeVariables& elemVolVars)
    {
        // Update only if the filler puts
        // solution-dependent stuff into the caches
        if (FluxVariablesCacheFiller::isSolDependent)
        {
            const auto& problem = gridFluxVarsCache().problem();
            const auto& gridGeometry = fvGeometry.gridGeometry();
            const auto& assemblyMapI = gridGeometry.connectivityMap()[gridGeometry.elementMapper().index(element)];
 
            // helper class to fill flux variables caches
            FluxVariablesCacheFiller filler(problem);
 
            // set all the caches to "outdated"
            for (auto& cache : fluxVarsCache_)
                cache.setUpdateStatus(false);
 
            // go through the caches maybe update them
            unsigned int i = 0;
            for (const auto& scvf : scvfs(fvGeometry))
            {
                auto& scvfCache = fluxVarsCache_[i++];
                if (!scvfCache.isUpdated())
                    filler.fill(*this, scvfCache, ivDataStorage_, fvGeometry, elemVolVars, scvf);
            }
 
            for (const auto& dataJ : assemblyMapI)
            {
                for (const auto scvfIdx : dataJ.scvfsJ)
                {
                    auto& scvfCache = fluxVarsCache_[i++];
                    if (!scvfCache.isUpdated())
                        filler.fill(*this, scvfCache, ivDataStorage_, fvGeometry, elemVolVars, fvGeometry.scvf(scvfIdx));
                }
            }
        }
    }
 
    template<class SubControlVolumeFace, typename std::enable_if_t<!std::is_integral<SubControlVolumeFace>::value, int> = 0>
    const FluxVariablesCache& operator [](const SubControlVolumeFace& scvf) const
    { return fluxVarsCache_[getLocalScvfIdx_(scvf.index())]; }
 
    const FluxVariablesCache& operator [](const std::size_t scvfIdx) const
    { return fluxVarsCache_[getLocalScvfIdx_(scvfIdx)]; }
 
    template<class SubControlVolumeFace, typename std::enable_if_t<!std::is_integral<SubControlVolumeFace>::value, int> = 0>
    FluxVariablesCache& operator [](const SubControlVolumeFace& scvf)
    { return fluxVarsCache_[getLocalScvfIdx_(scvf.index())]; }
 
    FluxVariablesCache& operator [](const std::size_t scvfIdx)
    { return fluxVarsCache_[getLocalScvfIdx_(scvfIdx)]; }
 
    template<class SubControlVolumeFace>
    const PrimaryInteractionVolume& primaryInteractionVolume(const SubControlVolumeFace& scvf) const
    { return ivDataStorage_.primaryInteractionVolumes[ (*this)[scvf].ivIndexInContainer() ]; }
 
    template<class SubControlVolumeFace>
    const PrimaryIvDataHandle& primaryDataHandle(const SubControlVolumeFace& scvf) const
    { return ivDataStorage_.primaryDataHandles[ (*this)[scvf].ivIndexInContainer() ]; }
 
    template<class SubControlVolumeFace>
    const SecondaryInteractionVolume& secondaryInteractionVolume(const SubControlVolumeFace& scvf) const
    { return ivDataStorage_.secondaryInteractionVolumes[ (*this)[scvf].ivIndexInContainer() ]; }
 
    template<class SubControlVolumeFace>
    const SecondaryIvDataHandle& secondaryDataHandle(const SubControlVolumeFace& scvf) const
    { return ivDataStorage_.secondaryDataHandles[ (*this)[scvf].ivIndexInContainer() ]; }
 
    const GridFluxVariablesCache& gridFluxVarsCache() const
    {  return *gridFluxVarsCachePtr_; }
 
private:
    const GridFluxVariablesCache* gridFluxVarsCachePtr_;
 
    void clear_()
    {
        fluxVarsCache_.clear();
        globalScvfIndices_.clear();
        ivDataStorage_.primaryInteractionVolumes.clear();
        ivDataStorage_.secondaryInteractionVolumes.clear();
        ivDataStorage_.primaryDataHandles.clear();
        ivDataStorage_.secondaryDataHandles.clear();
    }
 
    unsigned int getLocalScvfIdx_(const int scvfIdx) const
    {
        auto it = std::find(globalScvfIndices_.begin(), globalScvfIndices_.end(), scvfIdx);
        assert(it != globalScvfIndices_.end() && "Could not find the flux vars cache for scvfIdx");
        return std::distance(globalScvfIndices_.begin(), it);
    }
 
    // the local flux vars caches and corresponding indices
    std::vector<FluxVariablesCache> fluxVarsCache_;
    std::vector<std::size_t> globalScvfIndices_;
 
    // stored interaction volumes and handles
    using IVDataStorage = InteractionVolumeDataStorage<PrimaryInteractionVolume,
                                                       PrimaryIvDataHandle,
                                                       SecondaryInteractionVolume,
                                                       SecondaryIvDataHandle>;
    IVDataStorage ivDataStorage_;
};
 
} // end namespace
 
#endif