solution_function.h

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2026 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 SOLUTION_FUNCTION_H
#define SOLUTION_FUNCTION_H
 
// libMesh includes
#include "libmesh/function_base.h"
 
// Example includes
#include "laplace_exact_solution.h"
 
// C++ includes
#include <memory>
 
using namespace libMesh;
 
class SolutionFunction : public FunctionBase<Number>
{
public:
 
  SolutionFunction (const unsigned int u_var) :
    _u_var(u_var) {}
 
  ~SolutionFunction() = default;
 
  virtual Number operator() (const Point &,
                             const Real = 0)
  { libmesh_not_implemented(); }
 
  virtual void operator() (const Point & p,
                           const Real,
                           DenseVector<Number> & output)
  {
    output.zero();
    const Real x=p(0), y=p(1), z=p(2);
    // libMesh assumes each component of the vector-valued variable is stored
    // contiguously.
    output(_u_var)   = soln(0, x, y, z);
    output(_u_var+1) = soln(1, x, y, z);
    output(_u_var+2) = soln(2, x, y, z);
  }
 
  virtual Number component(unsigned int component_in,
                           const Point & p,
                           const Real)
  {
    const Real x=p(0), y=p(1), z=p(2);
    return soln(component_in, x, y, z);
  }
 
  virtual std::unique_ptr<FunctionBase<Number>> clone() const
  { return std::make_unique<SolutionFunction>(_u_var); }
 
private:
 
  const unsigned int _u_var;
  LaplaceExactSolution soln;
};
 
//FIXME: PB: We ought to be able to merge the above class with this one
//           through templating, but I'm being lazy.
class SolutionGradient : public FunctionBase<Gradient>
{
public:
 
  SolutionGradient(const unsigned int u_var)
    : _u_var(u_var) {}
  ~SolutionGradient() = default;
 
  virtual Gradient operator() (const Point &, const Real = 0)
  { libmesh_not_implemented(); }
 
  virtual void operator() (const Point & p,
                           const Real,
                           DenseVector<Gradient>& output)
  {
    output.zero();
    const Real x=p(0), y=p(1), z=p(2);
    output(_u_var)   = soln(0, x, y, z);
    output(_u_var+1) = soln(1, x, y, z);
    output(_u_var+2) = soln(2, x, y, z);
  }
 
  virtual Gradient component(unsigned int component_in,
                             const Point & p,
                             const Real)
  {
    const Real x=p(0), y=p(1), z=p(2);
    return soln(component_in, x, y, z);
  }
 
  virtual std::unique_ptr<FunctionBase<Gradient>> clone() const
  { return std::make_unique<SolutionGradient>(_u_var); }
 
private:
 
  const unsigned int _u_var;
  LaplaceExactGradient soln;
};
 
#endif // SOLUTION_FUNCTION_H