FlatPreBasis.hpp

#pragma once

#include <dune/functions/functionspacebases/basistags.hh>
#include <dune/functions/functionspacebases/compositebasis.hh>
#include <dune/functions/functionspacebases/powerbasis.hh>

#include <amdis/Output.hpp>

namespace AMDiS
{

  template <class PreBasis>
  struct FlatPreBasis
  {
    using type = PreBasis;

    template <class PB>
    static type create(PB const& preBasis)
    {
      return {preBasis.gridView()};
    }

    static PreBasis const& create(PreBasis const& preBasis)
    {
      return preBasis;
    }
  };

  template <class PreBasis>
  using FlatPreBasis_t = typename FlatPreBasis<PreBasis>::type;

  template <class PreBasis>
  decltype(auto) flatPreBasis(PreBasis const& preBasis)
  {
    return FlatPreBasis<PreBasis>::create(preBasis);
  }


  template <class IMS>
  struct FlatIndexMergingStrategy
  {
    using type = IMS;
  };

  // specialization for BlockedInterleaved
  template <>
  struct FlatIndexMergingStrategy<Dune::Functions::BasisFactory::BlockedInterleaved>
  {
    using type = Dune::Functions::BasisFactory::FlatInterleaved;
  };

  // specialization for BlockedLexicographic
  template <>
  struct FlatIndexMergingStrategy<Dune::Functions::BasisFactory::BlockedLexicographic>
  {
    using type = Dune::Functions::BasisFactory::FlatLexicographic;
  };

  // specialization for composite bases
  template <class IMS, class... SPB>
  struct FlatPreBasis<Dune::Functions::CompositePreBasis<IMS, SPB...>>
  {
    using FIMS = typename FlatIndexMergingStrategy<IMS>::type;
    using type = Dune::Functions::CompositePreBasis<FIMS, FlatPreBasis_t<SPB>...>;

    template <class PreBasis>
    static type create(PreBasis const& preBasis)
    {
      return create(preBasis, std::index_sequence_for<SPB...>{});
    }

    template <class PreBasis, std::size_t... I>
    static type create(PreBasis const& preBasis, std::index_sequence<I...>)
    {
      test_warning(std::is_same_v<IMS,FIMS>, "Basis converted into flat index-merging strategy.");
      return {FlatPreBasis<SPB>::create(preBasis.subPreBasis(Dune::index_constant<I>{}))...};
    }
  };

  // specialization for power bases
  template <class IMS, class SPB, std::size_t C>
  struct FlatPreBasis<Dune::Functions::PowerPreBasis<IMS, SPB, C>>
  {
    using FIMS = typename FlatIndexMergingStrategy<IMS>::type;
    using type = Dune::Functions::PowerPreBasis<FIMS, FlatPreBasis_t<SPB>, C>;

    template <class PreBasis>
    static type create(PreBasis const& preBasis)
    {
      test_warning(std::is_same_v<IMS,FIMS>, "Basis converted into flat index-merging strategy.");
      return type{FlatPreBasis<SPB>::create(preBasis.subPreBasis())};
    }
  };

} // end namespace AMDiS