ref_tetrahedron.hpp

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// Copyright (C) 2025 Tiago V. L. Amorim (@tiagovla)
//
// This file is part of oiseau (https://github.com/tiagovla/oiseau)
//
// SPDX-License-Identifier: GPL-3.0-or-later
 
#pragma once
#include <xtensor/core/xtensor_forward.hpp>
 
#include "oiseau/dg/nodal/ref_element.hpp"

 
namespace oiseau::dg::nodal {

class RefTetrahedron : public RefElement {
 public:
  explicit RefTetrahedron(unsigned order);

  xt::xarray<double> basis_function(const xt::xarray<double> &rst, int i, int j, int k) const;

  xt::xarray<double> grad_basis_function(const xt::xarray<double> &rst, int i, int j, int k) const;
 
 private:
  xt::xarray<double> vandermonde(const xt::xarray<double> &rst) const;

  xt::xarray<double> grad_vandermonde(const xt::xarray<double> &rst) const;

  xt::xarray<double> grad_operator(const xt::xarray<double> &v, const xt::xarray<double> &gv) const;
};
 
namespace detail {

xt::xarray<double> equilateral_xyz_to_rst(const xt::xarray<double> &coords);

xt::xarray<double> rst_to_abc(const xt::xarray<double> &rst);

xt::xarray<double> generate_tetrahedron_nodes(unsigned p);

xt::xarray<double> generate_tetrahedron_equidistant_nodes(unsigned n);

xt::xarray<double> warp_shift_face_3d(int p, double pval, const xt::xarray<double> &l2,
                                      const xt::xarray<double> &l3, const xt::xarray<double> &l4);
xt::xarray<double> eval_shift(int p, double pval, const xt::xarray<double> &l1,
                              const xt::xarray<double> &l2, const xt::xarray<double> &l3);
xt::xarray<double> eval_warp(int p, const xt::xarray<double> &xnodes,
                             const xt::xarray<double> &xout);
 
}  // namespace detail
 
}  // namespace oiseau::dg::nodal