fem_function_base.h

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// The libMesh Finite Element Library.
// Copyright (C) 2002-2023 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_FEM_FUNCTION_BASE_H
#define LIBMESH_FEM_FUNCTION_BASE_H

// Local Includes
#include "libmesh/libmesh_common.h"
#include "libmesh/dense_vector.h" // required to instantiate a DenseVector<> below
#include "libmesh/fem_context.h"

// C++ includes
#include <memory>

namespace libMesh
{

template <typename Output=Number>
class FEMFunctionBase
{
protected:

  FEMFunctionBase () = default;

public:

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

  virtual void init_context (const FEMContext &) {}

  virtual std::unique_ptr<FEMFunctionBase<Output>> clone () const = 0;

  virtual Output operator() (const FEMContext &,
                             const Point & p,
                             const Real time = 0.) = 0;

  void operator() (const FEMContext &,
                   const Point & p,
                   DenseVector<Output> & output);

  virtual void operator() (const FEMContext &,
                           const Point & p,
                           const Real time,
                           DenseVector<Output> & output) = 0;

  virtual Output component(const FEMContext &,
                           unsigned int i,
                           const Point & p,
                           Real time=0.);
};

template <typename Output>
inline
Output FEMFunctionBase<Output>::component (const FEMContext & context,
                                           unsigned int i,
                                           const Point & p,
                                           Real time)
{
  DenseVector<Output> outvec(i+1);
  (*this)(context, p, time, outvec);
  return outvec(i);
}

template <typename Output>
inline
void FEMFunctionBase<Output>::operator() (const FEMContext & context,
                                          const Point & p,
                                          DenseVector<Output> & output)
{
  // 调用时间相关的函数，t=0。
  this->operator()(context, p, 0., output);
}

} // namespace libMesh
#endif // LIBMESH_FEM_FUNCTION_BASE_H