variablesbackend.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_COMMON_VARIABLES_BACKEND_HH
#define DUMUX_COMMON_VARIABLES_BACKEND_HH
 
#include <array>
#include <utility>
#include <type_traits>
 
#include <dune/common/indices.hh>
#include <dune/common/typetraits.hh>
#include <dune/common/hybridutilities.hh>
#include <dune/common/std/type_traits.hh>
#include <dune/common/typetraits.hh>
#include <dune/istl/bvector.hh>
 
#include <dumux/common/typetraits/isvalid.hh>
 
// forward declaration
namespace Dune {
 
template<class... Args>
class MultiTypeBlockVector;
 
} // end namespace Dune
 
namespace Dumux::Detail::DofBackend {
 
struct HasResize
{
    template<class V>
    auto operator()(const V& v) -> decltype(std::declval<V>().resize(0))
    {}
};
 
template<class Vector>
static constexpr auto hasResize()
{ return decltype( isValid(HasResize())(std::declval<Vector>()) )::value; }
 
} // end namespace Dumux::Detail::VariablesBackend
 
namespace Dumux {
 
template<class DofVector, bool isScalar = Dune::IsNumber<DofVector>::value>
class DofBackend;
 
template<class Scalar>
class DofBackend<Scalar, true>
{
public:
    using DofVector = Scalar; 
    using SizeType = std::size_t;
 
    static SizeType size(const DofVector& d)
    { return 1; }
 
    static DofVector zeros(SizeType size)
    { return 0.0; }
 
    template<class OtherDofVector>
    static void axpy(Scalar a, const OtherDofVector& x, DofVector& y)
    { y += a*x; }
};
 
template<class Vector>
class DofBackend<Vector, false>
{
public:
    using DofVector = Vector; 
    using SizeType = std::size_t;
 
    static SizeType size(const DofVector& d)
    { return d.size(); }
 
    static DofVector zeros(SizeType size)
    {
        DofVector d;
        if constexpr (Detail::DofBackend::hasResize<Vector>())
            d.resize(size);
        return d;
    }
 
    template<class OtherDofVector>
    static void axpy(typename DofVector::field_type a, const OtherDofVector& x, DofVector& y)
    {
        for (typename DofVector::size_type i = 0; i < y.size(); ++i)
        {
            if constexpr (Dune::IsNumber<std::decay_t<decltype(y[0])>>::value)
                y[i] += a*x[i];
            else
                y[i].axpy(a, x[i]);
        }
    }
};
 
template<class... Blocks>
class DofBackend<Dune::MultiTypeBlockVector<Blocks...>, false>
{
    using DV = Dune::MultiTypeBlockVector<Blocks...>;
    static constexpr auto numBlocks = DV::size();
 
    using VectorSizeInfo = std::array<std::size_t, numBlocks>;
 
public:
    using DofVector = DV; 
    using SizeType = VectorSizeInfo;
 
    static SizeType size(const DofVector& d)
    {
        VectorSizeInfo result;
        using namespace Dune::Hybrid;
        forEach(std::make_index_sequence<numBlocks>{}, [&](auto i) {
            result[i] = d[Dune::index_constant<i>{}].size();
        });
        return result;
    }
 
    static DofVector zeros(const SizeType& size)
    {
        DofVector result;
        using namespace Dune::Hybrid;
        forEach(std::make_index_sequence<numBlocks>{}, [&](auto i) {
            result[Dune::index_constant<i>{}].resize(size[i]);
        });
        return result;
    }
 
    template<class Scalar, class OtherDofVector, std::enable_if_t< Dune::IsNumber<Scalar>::value, int> = 0>
    static void axpy(Scalar a, const OtherDofVector& x, DofVector& y)
    {
        using namespace Dune::Hybrid;
        forEach(std::make_index_sequence<numBlocks>{}, [&](auto i) {
            DofBackend<std::decay_t<decltype(y[Dune::index_constant<i>{}])>>::axpy(
                a, x[Dune::index_constant<i>{}], y[Dune::index_constant<i>{}]
            );
        });
    }
};
 
namespace Detail {
 
template<class Vars>
using SolutionVectorType = typename Vars::SolutionVector;
 
template<class Vars, bool varsExportSolution>
class VariablesBackend;
 
template<class Vars>
class VariablesBackend<Vars, false>
: public Dumux::DofBackend<Vars>
{
    using ParentType = Dumux::DofBackend<Vars>;
 
public:
    using Variables = Vars;
    using typename ParentType::DofVector;
 
    static void update(Variables& v, const DofVector& dofs)
    { v = dofs; }
 
    static const DofVector& dofs(const Variables& v)
    { return v; }
 
    static DofVector& dofs(Variables& v)
    { return v; }
};
 
template<class Vars>
class VariablesBackend<Vars, true>
: public Dumux::DofBackend<typename Vars::SolutionVector>
{
public:
    using DofVector = typename Vars::SolutionVector;
    using Variables = Vars; 
 
    static void update(Variables& v, const DofVector& dofs)
    { v.update(dofs); }
 
    static const DofVector& dofs(const Variables& v)
    { return v.dofs(); }
 
    static DofVector& dofs(Variables& v)
    { return v.dofs(); }
};
} // end namespace Detail
 
template<class Vars>
using VariablesBackend = Detail::VariablesBackend<Vars, Dune::Std::is_detected_v<Detail::SolutionVectorType, Vars>>;
 
} // end namespace Dumux
 
#endif