utils/basis.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 <utility>
 
#include <dune/functions/functionspacebases/defaultglobalbasis.hh>
 
#include <ikarus/utils/flatprebasis.hh>
 
namespace Ikarus {
 
template <typename PB>
class BasisHandler
{
public:
  using PreBasis = PB;                          
  using GridView = typename PreBasis::GridView; 
  using UntouchedBasis =
      decltype(Dune::Functions::DefaultGlobalBasis(std::declval<PreBasis>())); 
  using FlatBasis = decltype(Dune::Functions::DefaultGlobalBasis(
      Ikarus::flatPreBasis(std::declval<PreBasis>()))); 
 
  explicit BasisHandler(const PreBasis& pb)
      : bb_{Dune::Functions::DefaultGlobalBasis(pb)},
        fb_{Dune::Functions::DefaultGlobalBasis(Ikarus::flatPreBasis(pb))} {}
 
  auto& flat() { return fb_; }
 
  auto& untouched() { return bb_; }
 
  const auto& flat() const { return fb_; }
 
  const auto& untouched() const { return bb_; }
 
  const auto& gridView() const { return bb_.gridView(); }
 
  auto& gridView() { return bb_.gridView(); }
 
private:
  UntouchedBasis bb_;
  FlatBasis fb_;
};
 
template <typename GV, typename PBF>
auto makeBasis(const GV& gv, const PBF& pb) {
  auto preBasis = pb(gv);
  return BasisHandler(preBasis);
}
 
template <typename PB>
auto makeBasis(const Dune::Functions::DefaultGlobalBasis<PB>& gb) {
  return BasisHandler(gb.preBasis());
}
} // namespace Ikarus