smoothness_estimator.h

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2025 Benjamin S. Kirk, John W. Peterson, Roy H. Stogner

// This library is free software; you can redistribute it and/or
// modify it under the terms of the GNU Lesser General Public
// License as published by the Free Software Foundation; either
// version 2.1 of the License, or (at your option) any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
// Lesser General Public License for more details.

// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, write to the Free Software
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA



#ifndef LIBMESH_SMOOTHNESS_ESTIMATOR_H
#define LIBMESH_SMOOTHNESS_ESTIMATOR_H

// Local Includes
#include "libmesh/point.h"
#include "libmesh/elem_range.h"

// C++ includes
#include <cstddef>
#include <vector>

namespace libMesh
{

// Forward Declarations
class ErrorVector;
class System;
class Elem;
enum Order : int;

class SmoothnessEstimator
{
public:

  SmoothnessEstimator();

  SmoothnessEstimator (const SmoothnessEstimator &) = default;
  SmoothnessEstimator (SmoothnessEstimator &&) = default;
  SmoothnessEstimator & operator= (const SmoothnessEstimator &) = default;
  SmoothnessEstimator & operator= (SmoothnessEstimator &&) = default;
  virtual ~SmoothnessEstimator() = default;

  virtual void estimate_smoothness (const System & system,
                               ErrorVector & smoothness_per_cell,
                               const NumericVector<Number> * solution_vector = nullptr);

  void extra_quadrature_order (const int extraorder)
  { _extra_order = extraorder; }

protected:

  static std::vector<Real> legepoly(const unsigned int dim,
                                    const Order order,
                                    const Point p,
                                    const unsigned int matsize);

  int _extra_order;

  static Real compute_slope(int N, Real Sx, Real Sy, Real Sxx, Real Sxy);

  void reduce_smoothness (std::vector<ErrorVectorReal> & error_per_cell,
                          const Parallel::Communicator & comm);

private:

  class EstimateSmoothness
  {
  public:
    EstimateSmoothness (const System & sys,
                   const SmoothnessEstimator & ee,
                   ErrorVector & epc) :
      system(sys),
      smoothness_estimator(ee),
      smoothness_per_cell(epc)
    {}

    void operator()(const ConstElemRange & range) const;

  private:
    const System & system;
    const SmoothnessEstimator & smoothness_estimator;
    ErrorVector & smoothness_per_cell;
  };

  friend class EstimateSmoothness;
};


} // namespace libMesh


#endif // LIBMESH_SMOOTHNESS_ESTIMATOR_H