functionhelper.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
 
namespace Ikarus::utils {
  template <int size, typename LocalView>
  void obtainLagrangeNodePositions(const LocalView& localView,
                                   std::vector<Dune::FieldVector<double, size>>& lagrangeNodeCoords) {
    static_assert(Concepts::LagrangeNode<std::remove_cvref_t<decltype(localView.tree().child(0))>>,
                  "This function is only supported for Lagrange basis");
    assert(localView.bound() && "The local view must be bound to an element");
    const auto& localFE = localView.tree().child(0).finiteElement();
    lagrangeNodeCoords.resize(localFE.size());
    std::vector<double> out;
    for (int i = 0; i < size; i++) {
      auto ithCoord = [&i](const Dune::FieldVector<double, size>& x) { return x[i]; };
      localFE.localInterpolation().interpolate(ithCoord, out);
      for (std::size_t j = 0; j < out.size(); j++)
        lagrangeNodeCoords[j][i] = out[j];
    }
    for (auto& nCoord : lagrangeNodeCoords)
      nCoord = localView.element().geometry().global(nCoord);
  }
 
}  // namespace Ikarus::utils