Operator.h 97.7 KB
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// ============================================================================
// ==                                                                        ==
// == AMDiS - Adaptive multidimensional simulations                          ==
// ==                                                                        ==
// ============================================================================
// ==                                                                        ==
// ==  crystal growth group                                                  ==
// ==                                                                        ==
// ==  Stiftung caesar                                                       ==
// ==  Ludwig-Erhard-Allee 2                                                 ==
// ==  53175 Bonn                                                            ==
// ==  germany                                                               ==
// ==                                                                        ==
// ============================================================================
// ==                                                                        ==
// ==  http://www.caesar.de/cg/AMDiS                                         ==
// ==                                                                        ==
// ============================================================================

/** \file Operator.h */

#ifndef AMDIS_OPERATOR_H
#define AMDIS_OPERATOR_H

#include <vector>
#include "FixVec.h"
#include "Flag.h"
#include "MemoryManager.h"
#include "MatrixVector.h"
#include "ElInfo.h"
#include "AbstractFunction.h"
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#include "OpenMP.h"
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#include "SubAssembler.h"
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namespace AMDiS {

  class Assembler;
  class ElInfo;
  class FiniteElemSpace;
  class Operator;
  class SubAssembler;
  class ElementMatrix;
  class ElementVector;
  class Quadrature;
  template<typename T> class DOFVectorBase;

  // ============================================================================
  // ===== class OperatorTerm ===================================================
  // ============================================================================

  /** 
   * \ingroup Assembler
   * 
   * \brief
   * Base class for ZeroOrderTerm, FirstOrderTerm and SecondOrderTerm. 
   * OperatorTerms are the building blocks of an Operator. Each OperatorTerm
   * has its properties which are regarded, when constructing 
   * an Assembler for the corresponding Operator.
   */
  class OperatorTerm
  {
  public:
    MEMORY_MANAGED(OperatorTerm);

    /** \brief
     * Constructs an OperatorTerm with initially no properties.
     * degree_ is used to determine the degree of the needed quadrature
     * for the assemblage.  
     */
    OperatorTerm(int degree_) 
      : properties(0), 
	degree(degree_) 
    {};

    /** \brief
     * Destructor.
     */
    virtual ~OperatorTerm() {};

    /** \brief
     * Virtual method. It's called by SubAssembler::initElement() for
     * each OperatorTerm belonging to this SubAssembler. Here e.g. vectors
     * and coordinates at quadrature points can be calculated.
     */
    virtual void initElement(const ElInfo*, 
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			     SubAssembler*,
			     Quadrature *quad = NULL) 
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    {};

    /** \brief
     * Specifies whether the matrix of the term is symmetric
     */
    void setSymmetric(bool symm);

    /** \brief
     * Returns true, if the term is piecewise constant, returns false otherwise
     */
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    inline bool isPWConst() { 
      return (degree == 0);
    };
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    /** \brief
     * Returns true, if the term has a symmetric matrix, 
     * returns false otherwise.
     */
    bool isSymmetric();

    /** \brief
     * Returns \ref degree.
     */
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    inline int getDegree() { 
      return degree; 
    };
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    /** \brief
     * Evaluation of the OperatorTerm at all quadrature points.
     */
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    virtual void eval(int nPoints,
		      const double *uhAtQP,
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		      const WorldVector<double> *grdUhAtQP,
		      const WorldMatrix<double> *D2UhAtQP,
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		      double *result,
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		      double factor) const = 0;

  protected:
    /** \brief
     * Evaluation of \f$ \Lambda \cdot A \cdot \Lambda^t\f$.
     */
    static void lalt(const DimVec<WorldVector<double> >& Lambda,
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		     const WorldMatrix<double>& matrix,
		     DimMat<double>& LALt,
		     bool symm,
		     double factor);
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    /** \brief
     * Evaluation of \f$ \Lambda \cdot A \cdot \Lambda^t\f$ for \f$ A \f$
     * the matrix having a ONE in the position \f$ (K,L) \f$
     * and ZEROS in all other positions.
     */
    static void lalt_kl(const DimVec<WorldVector<double> >& Lambda,
			int k, int l,
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			DimMat<double>& LALt,
			double factor);
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    /** \brief
     * Evaluation of \f$ \Lambda \cdot A \cdot \Lambda^t\f$ for A equal to the 
     * identity.
     */
    static void l1lt(const DimVec<WorldVector<double> >& Lambda,
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		     DimMat<double>& LALt,
		     double factor);
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    /** \brief
     * Evaluation of \f$ \Lambda \cdot b\f$.
     */
    static void lb(const DimVec<WorldVector<double> >& Lambda,
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		   const WorldVector<double>& b,
		   DimVec<double>& Lb,
		   double factor);
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    /** \brief
     * Evaluation of \f$ \Lambda \cdot b\f$ if b contains the value 1.0 in
     * each component.
     */
    static void l1(const DimVec<WorldVector<double> >& Lambda,
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		   DimVec<double>& Lb,
		   double factor)
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    {
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      int dim = Lb.getSize() - 1;
      static const int dimOfWorld = Global::getGeo(WORLD);
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      for (int i = 0; i <= dim; i++) {
	double val = 0.0;
      
	for (int j = 0; j < dimOfWorld; j++) {
	  val += Lambda[i][j];
	}
	val *= factor;
	Lb[i] += val;
      }    
    };

  protected:
    /** \brief
     * Stores the properties of this OperatorTerm
     */
    Flag properties;

    /** \brief
     * Polynomial degree of the term. Used to detemine the degree of the
     * quadrature.
     */
    int degree;

    /** \brief
     * Pointer to the Operator this OperatorTerm belongs to.
     */
    Operator* operat;

    /** \brief
     * Constant Flag for piecewise constant terms
     */
    static const Flag PW_CONST;

    /** \brief
     * Constant Flag for symmetric terms
     */
    static const Flag SYMMETRIC;

    friend class SubAssembler;
    friend class ZeroOrderAssembler;
    friend class FirstOrderAssembler;
    friend class SecondOrderAssembler;
    friend class Operator;
  };

  // ============================================================================
  // =====  class SecondOrderTerm ===============================================
  // ============================================================================

  /**
   * \ingroup Assembler
   * 
   * \brief
   * Describes the second order terms: \f$ \nabla \cdot A \nabla u(\vec{x}) \f$
   */
  class SecondOrderTerm : public OperatorTerm
  {
  public:
    /** \brief
     * Constructor.
     */
    SecondOrderTerm(int deg) : OperatorTerm(deg) {};

    /** \brief
     * Destructor.
     */
    virtual ~SecondOrderTerm() {};

    /** \brief
     * Evaluation of \f$ \Lambda A \Lambda^t \f$ at all quadrature points.
     */
    virtual void getLALt(const ElInfo *elInfo, 
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			 int nPoints, 
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			 DimMat<double> **result) const = 0;

    /** \brief
     * Evaluation of \f$ A \nabla u(\vec{x}) \f$ at all quadrature points.
     */
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    virtual void weakEval(int nPoints,
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			  const WorldVector<double> *grdUhAtQP,
			  WorldVector<double> *result) const = 0;

  };

  // ============================================================================

  /**
   * \ingroup Assembler
   * 
   * \brief
   * Implements the laplace operator: \f$ \Delta u(\vec{x}) \f$
   */
  class Laplace_SOT : public SecondOrderTerm 
  {
  public:
    /** \brief
     * Constructor.
     */
    Laplace_SOT() 
      : SecondOrderTerm(0) 
    {
      setSymmetric(true);
    };

    /** \brief
     * Implenetation of SecondOrderTerm::getLALt().
     */
    inline void getLALt(const ElInfo *elInfo, int numPoints, DimMat<double> **LALt) const
    {
      const DimVec<WorldVector<double> > &Lambda = elInfo->getGrdLambda();

      for (int iq = 0; iq < numPoints; iq++) {
	l1lt(Lambda, *(LALt[iq]), 1.0);
      }
    };

    /** \brief
     * Implementation of SecondOrderTerm::eval().
     */
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    inline void eval(int nPoints,
		     const double * ,    // uhAtQP
		     const WorldVector<double> * ,  // grdUhAtQP
		     const WorldMatrix<double> *D2UhAtQP,
		     double *result,
		     double factor) const
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    {
      int dow = Global::getGeo(WORLD);
    
      if (D2UhAtQP) {
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	for (int iq = 0; iq < nPoints; iq++) {
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	  double resultQP = 0.0;
	  for (int i = 0; i < dow; i++) {
	    resultQP += D2UhAtQP[iq][i][i];
	  }
	  result[iq] += factor * resultQP;
	}
      }
    };

    /** \brief
     * Implenetation of SecondOrderTerm::weakEval().
     */
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    void weakEval(int nPoints,
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		  const WorldVector<double> *grdUhAtQP,
		  WorldVector<double> *result) const
    {
      if (grdUhAtQP) {
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	for (int iq = 0; iq < nPoints; iq++) { 
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	  result[iq] += grdUhAtQP[iq];
	}
      }
    };
    };

  // ============================================================================

  /**
   * \ingroup Assembler
   * 
   * \brief
   * Implements the laplace operator multiplied with a scalar factor:
   * \f$ f \cdot \Delta u(\vec{x}) \f$
   */
  class FactorLaplace_SOT : public SecondOrderTerm 
  {
  public:
    /** \brief
     * Constructor.
     */
    FactorLaplace_SOT(double f) 
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      : SecondOrderTerm(0)  
    {
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      factor = new double;
      *factor = f;

      setSymmetric(true);
    };

    /** \brief
     * Constructor.
     */
    FactorLaplace_SOT(double *fptr) 
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      : SecondOrderTerm(0), 
	factor(fptr)
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    {
      setSymmetric(true);
    };

    /** \brief
     * Implements SecondOrderTerm::getLALt().
     */
    inline void getLALt(const ElInfo *elInfo, int numPoints, DimMat<double> **LALt) const
    {
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      const DimVec<WorldVector<double> > &Lambda = elInfo->getGrdLambda();
      for (int iq = 0; iq < numPoints; iq++) 
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	l1lt(Lambda, *(LALt[iq]), (*factor));
    };


    /** \brief
     * Implenetation of SecondOrderTerm::eval().
     */
    void eval(int numPoints,
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	      const double *,
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	      const WorldVector<double> *,
	      const WorldMatrix<double> *D2UhAtQP,
	      double *result,
	      double f) const
    {
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      int dow = Global::getGeo(WORLD);
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      if (D2UhAtQP) {
	for (int iq = 0; iq < numPoints; iq++) {
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	  double resultQP = 0.0;
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	  for (int i = 0; i < dow; i++) {
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	    resultQP += D2UhAtQP[iq][i][i];
	  }
	  result[iq] += resultQP * f * (*factor);
	}
      }
    };

    /** \brief
     * Implenetation of SecondOrderTerm::weakEval().
     */
    void weakEval(int numPoints,
		  const WorldVector<double> *grdUhAtQP,
		  WorldVector<double> *result) const
    {
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      if (grdUhAtQP) {
	for (int iq = 0; iq < numPoints; iq++) {
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	  axpy(*factor, grdUhAtQP[iq], result[iq]);
	}
      }
    };

  private:
    /** \brief
     * Pointer to the factor.
     */
    double *factor;
  };

  // ============================================================================

  /**
   * \ingroup Assembler
   * 
   * \brief
   * SecondOrderTerm where A is a function which maps a DOFVector evaluated at
   * a given quadrature point to a WolrdMatrix:
   * \f$ \nabla \cdot A(v(\vec{x})) \nabla u(\vec{x}) \f$
   */
  class MatrixFct_SOT : public SecondOrderTerm 
  {
  public:
    /** \brief
     * Constructor.
     */
    MatrixFct_SOT(DOFVectorBase<double> *dv, 
		  AbstractFunction<WorldMatrix<double>, double> *fct,
		  AbstractFunction<WorldVector<double>, WorldMatrix<double> > *div,
		  bool sym = false)
      : SecondOrderTerm(fct->getDegree()), 
	vec(dv), 
	matrixFct(fct), 
	divFct(div),
	symmetric(sym)
    {
      setSymmetric(symmetric);
    };

    /** \brief
     * Implementation of \ref OperatorTerm::initElement().
     */
    void initElement(const ElInfo* elInfo, SubAssembler* subAssembler,
		     Quadrature *quad = NULL);

    /** \brief
     * Implements SecondOrderTerm::getLALt().
     */
    void getLALt(const ElInfo *elInfo, int numPoints, DimMat<double> **LALt) const;
  
    /** \brief
     * Implenetation of SecondOrderTerm::eval().
     */
    void eval(int numPoints,
	      const double              *uhAtQP,
	      const WorldVector<double> *grdUhAtQP,
	      const WorldMatrix<double> *D2UhAtQP,
	      double *result,
	      double factor) const;

    /** \brief
     * Implenetation of SecondOrderTerm::weakEval().
     */
    void weakEval(int numPoints,
		  const WorldVector<double> *grdUhAtQP,
		  WorldVector<double> *result) const;

  protected:
    /** \brief
     * DOFVector to be evaluated at quadrature points.
     */
    DOFVectorBase<double>* vec;

    /** \brief
     * Pointer to the values of the DOFVector at quadrature points.
     */
    double* vecAtQPs;

    /** \brief
     * Function for A.
     */
    AbstractFunction<WorldMatrix<double>, double>* matrixFct;

    AbstractFunction<WorldVector<double>, WorldMatrix<double> >* divFct;

    /** \brief
     * True, if \ref matrixFct produces always symmetric matrices.
     */
    bool symmetric;
  };

  // ============================================================================

  /** 
   * \ingroup Assembler
   *
   * \brief
   * SecondOrderTerm where A is a given fixed WorldMatrix<double>:
   * \f$ \nabla \cdot A \nabla u(\vec{x}) \f$
   */
  class Matrix_SOT : public SecondOrderTerm {
  public:
    /** \brief
     * Constructor
     */
    Matrix_SOT(WorldMatrix<double> mat) 
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      : SecondOrderTerm(0),
	matrix(mat)
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    {
      symmetric = matrix.isSymmetric();
      setSymmetric(symmetric);
    };

    /** \brief
     * Implements SecondOrderTerm::getLALt().
     */
    inline void getLALt(const ElInfo *elInfo, int numPoints, DimMat<double> **LALt) const{
      const DimVec<WorldVector<double> >& Lambda     = elInfo->getGrdLambda();
      //double det = elInfo->getDet();
      int iq;
      for(iq = 0; iq < numPoints; iq++) 
	lalt(Lambda, matrix, *(LALt[iq]), symmetric, 1.0);
    };
  
    /** \brief
     * Implenetation of SecondOrderTerm::eval().
     */
    void eval(int numPoints,
	      const double              *uhAtQP,
	      const WorldVector<double> *grdUhAtQP,
	      const WorldMatrix<double> *D2UhAtQP,
	      double *result,
	      double factor) const;

    /** \brief
     * Implenetation of SecondOrderTerm::weakEval().
     */
    void weakEval(int numPoints,
		  const WorldVector<double> *grdUhAtQP,
		  WorldVector<double> *result) const;

  protected:
    /** \brief
     * Matrix stroring A.
     */
    WorldMatrix<double> matrix;

    /** \brief
     * True, if \ref matrix is symmetric.
     */
    bool symmetric;
  };

  // ============================================================================

  /** 
   * \ingroup Assembler
   *
   * \brief
   * SecondOrderTerm where A is a WorldMatrix<double> having a ONE in position IJ
   * and ZERO in all other positions
   * \f$ \nabla \cdot A \nabla u(\vec{x}) \f$
   */
  class FactorIJ_SOT : public SecondOrderTerm 
  {
  public:
    /** \brief
     * Constructor.
     */
    FactorIJ_SOT(int x_i, int x_j, double f) 
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      : SecondOrderTerm(0), 
	xi(x_i), 
	xj(x_j)
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    {
      factor = new double;
      *factor = f;

      setSymmetric(xi == xj);
    };

    /** \brief
     * Constructor.
     */
    FactorIJ_SOT(int x_i, int x_j, double *fptr) 
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      : SecondOrderTerm(0), 
	xi(x_i), 
	xj(x_j), 
	factor(fptr)
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    {
      setSymmetric(xi == xj);
    };

    /** \brief
     * Implements SecondOrderTerm::getLALt().
     */
    inline void getLALt(const ElInfo *elInfo, int numPoints, DimMat<double> **LALt) const
    {
      const DimVec<WorldVector<double> > &Lambda     = elInfo->getGrdLambda();
      int iq;
      for(iq = 0; iq < numPoints; iq++)
	lalt_kl(Lambda, xi, xj, *(LALt[iq]), (*factor));
    };

    /** \brief
     * Implenetation of SecondOrderTerm::eval().
     */
    void eval(int numPoints,
	      const double              *,
	      const WorldVector<double> *,
	      const WorldMatrix<double> *D2UhAtQP,
	      double *result,
	      double fac) const
    {
      int iq;
      if(D2UhAtQP) {
	for(iq = 0; iq < numPoints; iq++) {
	  result[iq] += (*factor) * D2UhAtQP[iq][xi][xj] * fac;
	}
      }
    };

    /** \brief
     * Implenetation of SecondOrderTerm::weakEval().
     */
    void weakEval(int numPoints,
		  const WorldVector<double> *grdUhAtQP,
		  WorldVector<double> *result) const
    {
      if(grdUhAtQP) {
	int iq;
	for(iq = 0; iq < numPoints; iq++) {
	  result[iq][xi] += (*factor) * grdUhAtQP[iq][xj];
	}
      }
    };

  private:
    /** \brief
     * Directions for the derivatives.
     */
    int xi, xj;

    /** \brief
     * Pointer to the factor.
     */
    double *factor;
  };

  // ============================================================================

  /**
   * \ingroup Assembler
   *  
   * \brief
   * Laplace operator multiplied with a function evaluated at the quadrature
   * points of a given DOFVector:
   * \f$ f(v(\vec{x})) \Delta u(\vec{x}) \f$
   */
  class VecAtQP_SOT : public SecondOrderTerm {
  public:
    /** \brief
     * Constructor.
     */
    VecAtQP_SOT(DOFVectorBase<double> *dv, 
		AbstractFunction<double, double> *f_)
      : SecondOrderTerm(f_->getDegree()), vec(dv), f(f_)
    {
      setSymmetric(true);
    };

    /** \brief
     * Implementation of \ref OperatorTerm::initElement().
     */
    void initElement(const ElInfo* elInfo, SubAssembler* subAssembler,
		     Quadrature *quad = NULL);

    /** \brief
     * Implements SecondOrderTerm::getLALt().
     */
    void getLALt(const ElInfo *elInfo, int numPoints, DimMat<double> **LALt) const;    

    /** \brief
     * Implenetation of SecondOrderTerm::eval().
     */
    void eval(int numPoints,
	      const double              *uhAtQP,
	      const WorldVector<double> *grdUhAtQP,
	      const WorldMatrix<double> *D2UhAtQP,
	      double *result,
	      double factor) const;

    /** \brief
     * Implenetation of SecondOrderTerm::weakEval().
     */
    void weakEval(int numPoints,
		  const WorldVector<double> *grdUhAtQP,
		  WorldVector<double> *result) const;

  protected:
    /** \brief
     * DOFVector to be evaluated at quadrature points.
     */
    DOFVectorBase<double>* vec;

    /** \brief
     * Pointer to an array containing the DOFVector evaluated at quadrature
     * points.
     */
    double* vecAtQPs;

    /** \brief
     * Function evaluated at \ref vecAtQPs.
     */
    AbstractFunction<double, double> *f;
  };

  // ============================================================================

  /**
   * \ingroup Assembler
   * 
   * \brief
   * Laplace multiplied with a function evaluated at each quadrature point:
   * \f$ f(\vec{x}) \Delta u(\vec{x}) \f$
   */
  class CoordsAtQP_SOT : public SecondOrderTerm {
  public:
    /** \brief
     * Constructor.
     */
    CoordsAtQP_SOT(AbstractFunction<double, WorldVector<double> > *g_)
      : SecondOrderTerm(g_->getDegree()), g(g_)
    {
      setSymmetric(true);
    };

    /** \brief
     * Implementation of \ref OperatorTerm::initElement().
     */
    void initElement(const ElInfo* elInfo, SubAssembler* subAssembler,
		     Quadrature *quad = NULL);

    /** \brief
     * Implements SecondOrderTerm::getLALt().
     */
    void getLALt(const ElInfo *elInfo, int numPoints, DimMat<double> **LALt) const;    

    /** \brief
     * Implenetation of SecondOrderTerm::eval().
     */
    void eval(int numPoints,
	      const double              *uhAtQP,
	      const WorldVector<double> *grdUhAtQP,
	      const WorldMatrix<double> *D2UhAtQP,
	      double *result,
	      double factor) const;

    /** \brief
     * Implenetation of SecondOrderTerm::weakEval().
     */
    void weakEval(int numPoints,
		  const WorldVector<double> *grdUhAtQP,
		  WorldVector<double> *result) const;


  protected:
    /** \brief
     * Stores coordinates at quadrature points. Set in \ref initElement().
     */
    WorldVector<double>* coordsAtQPs;

    /** \brief
     * Function evaluated at quadrature points.
     */
    AbstractFunction<double, WorldVector<double> > *g;
  };

  // ============================================================================

  /**
   * \ingroup Assembler
   *
   * \brief
   * SecondOrderTerm where A is a function which maps the gradient of a 
   * DOFVector at each quadrature point to WorldMatrix<double>:
   * \f$ \nabla \cdot A(\nabla v(\vec{x})) \nabla u(\vec{x})\f$
   */
  class MatrixGradient_SOT : public SecondOrderTerm
  {
  public:
    /** \brief
     * Constructor.
     */
    MatrixGradient_SOT(DOFVectorBase<double> *dv,
		       AbstractFunction<WorldMatrix<double>, WorldVector<double> > *f_,
		       AbstractFunction<WorldVector<double>, WorldMatrix<double> > *divFct_,
		       bool symm = false) 
      : SecondOrderTerm(f_->getDegree()), vec(dv), f(f_), divFct(divFct_), symmetric(symm)
    {
      setSymmetric(symmetric);
    };

    /** \brief
     * Implementation of \ref OperatorTerm::initElement().
     */
    void initElement(const ElInfo* elInfo, SubAssembler* subAssembler,
		     Quadrature *quad = NULL);

    /** \brief
     * Implements SecondOrderTerm::getLALt().
     */
    void getLALt(const ElInfo *elInfo, int numPoints, DimMat<double> **LALt) const;

    /** \brief
     * Implenetation of SecondOrderTerm::eval().
     */
    void eval(int numPoints,
	      const double              *uhAtQP,
	      const WorldVector<double> *grdUhAtQP,
	      const WorldMatrix<double> *D2UhAtQP,
	      double *result,
	      double factor) const;

    /** \brief
     * Implenetation of SecondOrderTerm::weakEval().
     */
    void weakEval(int numPoints,
		  const WorldVector<double> *grdUhAtQP,
		  WorldVector<double> *result) const;

  protected:
    DOFVectorBase<double>* vec;

    /** \brief
     * Function which maps each entry in \ref gradAtQPs to a WorldMatrix<double>.
     */
    AbstractFunction<WorldMatrix<double>, WorldVector<double> > *f;

    AbstractFunction<WorldVector<double>, WorldMatrix<double> > *divFct;

    /** \brief
     * Pointer to a WorldVector<double> array containing the gradients of the DOFVector
     * at each quadrature point.
     */
    WorldVector<double>* gradAtQPs;

    /** \brief
     * True, if \ref f provides always a symmetric WorldMatrix<double>.
     */
    bool symmetric;
  };

  // ============================================================================

  /**
   * \ingroup Assembler
   *
   * \brief
   * Laplace multiplied with a function which maps the gradient of a DOFVector
   * at each quadrature point to a double:
   * \f$ f(\nabla v(\vec{x})) \Delta u(\vec{x}) \f$
   */
  class FctGradient_SOT : public SecondOrderTerm
  {
  public:
    /** \brief
     * Constructor.
     */
    FctGradient_SOT(DOFVectorBase<double> *dv,
		    AbstractFunction<double, WorldVector<double> > *f_)
      : SecondOrderTerm(f_->getDegree()), vec(dv), f(f_)
    {
    };

    /** \brief
     * Implementation of \ref OperatorTerm::initElement().
     */
    void initElement(const ElInfo* elInfo, SubAssembler* subAssembler,
		     Quadrature *quad = NULL);

    /** \brief
     * Implements SecondOrderTerm::getLALt().
     */
    void getLALt(const ElInfo *elInfo, int numPoints, DimMat<double> **LALt) const;

    /** \brief
     * Implenetation of SecondOrderTerm::eval().
     */
    void eval(int numPoints,
	      const double              *uhAtQP,
	      const WorldVector<double> *grdUhAtQP,
	      const WorldMatrix<double> *D2UhAtQP,
	      double *result,
	      double factor) const;

    /** \brief
     * Implenetation of SecondOrderTerm::weakEval().
     */
    void weakEval(int numPoints,
		  const WorldVector<double> *grdUhAtQP,
		  WorldVector<double> *result) const;

  protected:
    DOFVectorBase<double>* vec;

    /** \brief
     * Function wich maps \ref gradAtQPs to a double.
     */
    AbstractFunction<double, WorldVector<double> > *f;

    /** \brief
     * Pointer to a WorldVector<double> array containing the gradients of the DOFVector
     * at each quadrature point.
     */
    WorldVector<double>* gradAtQPs;
  };


  // Ergaenzung Andreas

  // ============================================================================

  /**
   * \ingroup Assembler
   *
   * \brief
   * Laplace multiplied with a function which maps the gradient of a DOFVector
   * at each quadrature point to a double:
   * \f$ f(\nabla v(\vec{x})) \Delta u(\vec{x}) \f$
   */
  class VecAndGradientAtQP_SOT : public SecondOrderTerm
  {
  public:
    /** \brief
     * Constructor.
     */
    VecAndGradientAtQP_SOT(DOFVectorBase<double> *dv,
			   BinaryAbstractFunction<double, double,
			   WorldVector<double> > *f_)
      : SecondOrderTerm(f_->getDegree()), vec(dv), f(f_)
    {
    };

    /** \brief
     * Implementation of \ref OperatorTerm::initElement().
     */
    void initElement(const ElInfo* elInfo, SubAssembler* subAssembler,
		     Quadrature *quad = NULL);

    /** \brief
     * Implements SecondOrderTerm::getLALt().
     */
    void getLALt(const ElInfo *elInfo, int numPoints, DimMat<double> **LALt) const;

    /** \brief
     * Implenetation of SecondOrderTerm::eval().
     */
    void eval(int numPoints,
	      const double              *uhAtQP,
	      const WorldVector<double> *grdUhAtQP,
	      const WorldMatrix<double> *D2UhAtQP,
	      double *result,
	      double factor) const;

    /** \brief
     * Implenetation of SecondOrderTerm::weakEval().
     */
    void weakEval(int numPoints,
		  const WorldVector<double> *grdUhAtQP,
		  WorldVector<double> *result) const;

  protected:
    DOFVectorBase<double>* vec;

    /** \brief
     * Function wich maps \ref gradAtQPs to a double.
     */
    BinaryAbstractFunction<double, double, WorldVector<double> > *f;

    /** \brief
     * Pointer to a WorldVector<double> array containing the gradients of the DOFVector
     * at each quadrature point.
     */
    double* vecAtQPs;
    WorldVector<double>* gradAtQPs;
  };


  // ============================================================================

  /**
   * \ingroup Assembler
   *
   * \brief
   * Laplace multiplied with a function which maps the gradient of a DOFVector
   * at each quadrature point to a double: