コード例 #1
0
ファイル: mrtr_projector.cpp プロジェクト: 00liujj/trilinos
/*----------------------------------------------------------------------*
 |                                                           mwgee 08/05|
 | 2D case:                                                             |
 | this method evaluates the function                                   |
 | F(eta) = ( Ni * xis - xm ) dot g(xi)                                 |
 | with Ni shape functions of slave segment                             |
 |      xm  nodal coords of master node                                 |
 |      xs  nodal coords of slave nodes on segment                      |
 |      njs nodal outward normal of nodes xs (slave side)               |
 *----------------------------------------------------------------------*/
double MOERTEL::Projector::evaluate_F_2D_SegmentOrthogonal(MOERTEL::Node& node,
                                                        MOERTEL::Segment& seg, 
                                                        double eta,
														double &gap)
{
  // check the type of function on the segment
  // Here, we need 1D functions set as function id 0
  MOERTEL::Function::FunctionType type = seg.FunctionType(0);
  if (type != MOERTEL::Function::func_Linear1D)
  {
	  std::stringstream oss;
    oss << "***ERR*** MOERTEL::Projector::evaluate_F_2D_SegmentOrthogonal:\n"
    	 << "***ERR*** function is of wrong type\n"
    	 << "***ERR*** file/line: " << __FILE__ << "/" << __LINE__ << "\n";
	throw ReportError(oss);
  }
  
  // evaluate the first function set on segment at eta
  int nsnode = seg.Nnode();
  double val[100];
  seg.EvaluateFunction(0,&eta,val,nsnode,NULL);
  
  // get nodal coords and normals of slave nodes and interpolate them
  double Nx[2]; 
  Nx[0] = Nx[1] = 0.0;
  MOERTEL::Node** snodes = seg.Nodes();
  if (!snodes)
  {
	  std::stringstream oss;
    oss << "***ERR*** MOERTEL::Projector::evaluate_F_2D_SegmentOrthogonal:\n"
    	 << "***ERR*** segment " << seg.Id() << " ptr to it's nodes is zero\n"
    	 << "***ERR*** file/line: " << __FILE__ << "/" << __LINE__ << "\n";
	throw ReportError(oss);
  }
  for (int i=0; i<nsnode; ++i)
  {
    const double* X = snodes[i]->X();
    Nx[0] += val[i]*X[0];
    Nx[1] += val[i]*X[1];
  }
  
  // subtract xm from interpolated coords Nx
  const double* X = node.X();
  Nx[0] -= X[0];
  Nx[1] -= X[1];
  
  // evaluate the metric of the segment in point xi
  double g[2];
  seg.Metric(&eta,g,NULL);

  // calculate F
  double F = Nx[0]*g[0] + Nx[1]*g[1];

  gap = (Nx[0] * g[0] + Nx[1] * g[1]);
		  
//  gap = ((Nx[0] - X[0]) * g[0] + (Nx[1] - X[1]) * g[1])
//		  / sqrt(g[0] * g[0] + g[1] * g[1]);  // ||gap|| cos theta

  return F;
}
コード例 #2
0
ファイル: mrtr_projector.cpp プロジェクト: 00liujj/trilinos
/*----------------------------------------------------------------------*
 |                                                           mwgee 08/05|
 | 2D case:                                                             |
 | this method evaluates the function                                   |
 | gradF(eta) =                                                         |
 |   ( Ni,eta * xis ) * ( Ni,eta * xis )                                |
 | with Ni,eta derivative of shape functions of segment                 |
 |      Ni,Nj shape functions of segment                                |
 |      xis nodal coords of segment's nodes i (slave side)              |
 *----------------------------------------------------------------------*/
double MOERTEL::Projector::evaluate_gradF_2D_SegmentOrthogonal_to_g(
                                                        MOERTEL::Node& node,
                                                        MOERTEL::Segment& seg, 
	      				                double eta,
                                                        double* g)
{
  // check the type of function on the segment
  // Here, we need 1D functions set as function id 0
  MOERTEL::Function::FunctionType type = seg.FunctionType(0);
  if (type != MOERTEL::Function::func_Linear1D)
  {
	  std::stringstream oss;
    oss << "***ERR*** MOERTEL::Projector::evaluate_gradF_2D_SegmentOrthogonal_to_g:\n"
    	 << "***ERR*** function is of wrong type\n"
    	 << "***ERR*** file/line: " << __FILE__ << "/" << __LINE__ << "\n";
	throw ReportError(oss);
  }
  
  // evaluate function and derivatives of the first function set on segment at eta
  int nmnode = seg.Nnode();
  double deriv[200];
  seg.EvaluateFunction(0,&eta,NULL,nmnode,deriv);
  
  // intermediate data:
  // Nxeta  = Ni,eta * xi
  
  // get nodal coords and normals of nodes and interpolate them
  double Nxeta[2];  Nxeta[0] = Nxeta[1] = 0.0;
  MOERTEL::Node** mnodes = seg.Nodes();
  if (!mnodes)
  {
	  std::stringstream oss;
    oss << "***ERR*** MOERTEL::Projector::evaluate_gradF_2D_SegmentOrthogonal_to_g:\n"
    	 << "***ERR*** segment " << seg.Id() << " ptr to it's nodes is zero\n"
    	 << "***ERR*** file/line: " << __FILE__ << "/" << __LINE__ << "\n";
	throw ReportError(oss);
  }
  for (int i=0; i<nmnode; ++i)
  {
    const double* X = mnodes[i]->X();
    Nxeta[0] += deriv[i]*X[0];
    Nxeta[1] += deriv[i]*X[1];
  }
  
  // calculate gradF
  double gradF =   Nxeta[0]*g[0] + Nxeta[1]*g[1];
  return gradF;
}
コード例 #3
0
/*----------------------------------------------------------------------*
 | project nodes master to slave along slave cont. normal field         |
 *----------------------------------------------------------------------*/
bool MOERTEL::Interface::ProjectNodes_MastertoSlave_NormalField()
{ 
  if (!IsComplete())
  {
	std::stringstream oss;
    oss << "***ERR*** MOERTEL::Interface::ProjectNodes_MastertoSlave_NormalField:\n"
         << "***ERR*** Complete() not called on interface " << Id() << "\n"
         << "***ERR*** file/line: " << __FILE__ << "/" << __LINE__ << "\n";
	throw ReportError(oss);
  }
  if (!lComm()) return true;
  
  int mside = MortarSide();
  int sside = OtherSide(mside);

  // iterate over all nodes of the master side and project those belonging to me
  std::map<int,Teuchos::RCP<MOERTEL::Node> >::iterator mcurr;
  for (mcurr=rnode_[mside].begin(); mcurr!=rnode_[mside].end(); ++mcurr)
  {
	Teuchos::RCP<MOERTEL::Node> mnode = mcurr->second;
    if (NodePID(mnode->Id()) != lComm()->MyPID())
      continue;
    
    const double* mx = mnode->X();
    double mindist = 1.0e+20;
	Teuchos::RCP<MOERTEL::Node> closenode = Teuchos::null;
    
    // find a node on the slave side that is closest to me
	std::map<int,Teuchos::RCP<MOERTEL::Node> >::iterator scurr;
    for (scurr=rnode_[sside].begin(); scurr!=rnode_[sside].end(); ++scurr)
    {
	  Teuchos::RCP<MOERTEL::Node> snode = scurr->second;
      const double* sx = snode->X();
      
      // build distance | snode->X() - mnode->X() |
      double dist = 0.0;
      for (int i=0; i<3; ++i) dist += (mx[i]-sx[i])*(mx[i]-sx[i]);
      dist = sqrt(dist);
      if (dist < mindist)
      {
        mindist = dist;
        closenode = snode;
      }
    } 
    if (closenode == Teuchos::null)
    {
	  std::stringstream oss;
      oss << "***ERR*** MOERTEL::Interface::ProjectNodes_MastertoSlave_NormalField:\n"
           << "***ERR*** Weired: for master node " << mnode->Id() << " no closest master node found\n"
           << "***ERR*** file/line: " << __FILE__ << "/" << __LINE__ << "\n";
		throw ReportError(oss);
    }

#if 0
    cout << "snode     " << *mnode;
    cout << "closenode " << *closenode;
#endif    
    
    // get segments attached to closest node closenode
    int  nseg = closenode->Nseg();
    MOERTEL::Segment** segs = closenode->Segments(); 
    
    // create a projection operator
    MOERTEL::Projector projector(IsOneDimensional(),OutLevel());
    
    // loop these segments and find best projection
    double bestdist[2];
    const double tol = 0.2;
	double bestgap = 0.0, gap;
    bestdist[0] = bestdist[1] = 1.0e+20;
    MOERTEL::Segment* bestseg = NULL;
    for (int i=0; i<nseg; ++i)
    {
      // project the master node on the slave segment along the segments interpolated normal field
      double xi[2]; xi[0] = xi[1] = 0.0;
      projector.ProjectNodetoSegment_SegmentNormal(*mnode,*(segs[i]),xi,gap);
      
      // check whether xi is better then previous projections
      if (IsOneDimensional())
      {
        if (abs(xi[0]) < abs(bestdist[0])) 
	{ 
	  bestdist[0] = xi[0];
	  bestdist[1] = xi[1];
	  bestseg = segs[i];
	  bestgap = gap;
	}
      }
      else
      {
        double third = 1./3.;
        // it's 'inside' with some tolerance
        if ( xi[0]<=1.+tol && xi[1]<=abs(1.-xi[0])+tol && xi[0]>=0.-tol && xi[1]>=0.-tol )
        {
          // it's better in both directions
          if ( sqrt((xi[0]-third)*(xi[0]-third)) < sqrt((bestdist[0]-third)*(bestdist[0]-third)) &&
               sqrt((xi[1]-third)*(xi[1]-third)) < sqrt((bestdist[1]-third)*(bestdist[1]-third)) )
	  {
	    bestdist[0] = xi[0];
	    bestdist[1] = xi[1];
	    bestseg = segs[i];
	    bestgap = gap;
	  }
	  //it's better in one direction and 'in' in the other
          else if (  (sqrt((xi[0]-third)*(xi[0]-third))<sqrt((bestdist[0]-third)*(bestdist[0]-third)) &&
                     xi[1]<=abs(1.-xi[0])+tol && xi[1]>=0.-tol ) ||
                     (sqrt((xi[1]-third)*(xi[1]-third))<sqrt((bestdist[1]-third)*(bestdist[1]-third)) &&
                     xi[0]<=1.+tol && xi[0]>=0.-tol ) )
	  {
	    bestdist[0] = xi[0];
	    bestdist[1] = xi[1];
	    bestseg = segs[i];
	    bestgap = gap;
	  }
        }
      }
    } // for (int i=0; i<nseg; ++i)
    
    // check whether the bestseg/bestdist are inside that segment
    // (with some tolerance of 20%)
    bool ok = false;
    if (IsOneDimensional())
    {
      if (abs(bestdist[0]) < 1.1) ok = true;
    }
    else
    {
      if (bestdist[0]<=1.+tol && bestdist[1]<=abs(1.-bestdist[0])+tol &&
          bestdist[0]>=0.-tol && bestdist[1]>=0.-tol) 
            ok = true;
    }
    
    if (ok) // the projection is good
    {
      // build the interpolated normal and overwrite the mnode normal with -n
      int          nsnode = bestseg->Nnode();
      MOERTEL::Node** snodes = bestseg->Nodes();
	  std::vector<double> val(nsnode);
      bestseg->EvaluateFunction(0,bestdist,&val[0],nsnode,NULL);
      double NN[3]; NN[0] = NN[1] = NN[2] = 0.0;
      for (int i=0; i<nsnode; ++i)
      {
        const double* N = snodes[i]->N();
        for (int j=0; j<3; ++j)
          NN[j] -= val[i]*N[j];
      }
      val.clear();
      mnode->SetN(NN);

      // create projected node and store it in mnode
      MOERTEL::ProjectedNode* pnode
        = new MOERTEL::ProjectedNode(*mnode,bestdist,bestseg);
      mnode->SetProjectedNode(pnode);
	  mnode->SetGap(bestgap);
    }
    else // this mnode does not have a valid projection
    {
      if (OutLevel()>6)
        cout << "MOERTEL: ***WRN***: Projection m->s: Node " << mnode->Id() << " does not have projection\n";
      mnode->SetProjectedNode(NULL);
    }
  } // for (scurr=rnode_[mside].begin(); scurr!=rnode_[mside].end(); ++scurr)

  // loop all master nodes again and make the projection and the new normal redundant
  int bsize = 7*rnode_[mside].size();
  std::vector<double> bcast(bsize);
  for (int proc=0; proc<lComm()->NumProc(); ++proc)
  {
    int blength = 0;
    if (proc==lComm()->MyPID())
    {
      for (mcurr=rnode_[mside].begin(); mcurr!=rnode_[mside].end(); ++mcurr)
      {
		Teuchos::RCP<MOERTEL::Node> mnode = mcurr->second;
        if (proc != NodePID(mnode->Id())) continue; // cannot have a projection on a node i don't own
		Teuchos::RCP<MOERTEL::ProjectedNode> pnode = mnode->GetProjectedNode();
        if (pnode == Teuchos::null) continue; // this node does not have a projection
        const double* xi = pnode->Xi();
        const double* N  = mnode->N();
        bcast[blength] = (double)pnode->Id();
        ++blength;
        if (pnode->Segment())
          bcast[blength] = (double)pnode->Segment()->Id();
        else
          bcast[blength] = -0.1;
        ++blength;
        bcast[blength] = xi[0];
        ++blength;
        bcast[blength] = xi[1];
        ++blength;
        bcast[blength] = N[0];
        ++blength;
        bcast[blength] = N[1];
        ++blength;
        bcast[blength] = N[2];
        ++blength;
        bcast[blength] = pnode->Gap();
        ++blength;
      }
      if (blength > bsize)
      {
		std::stringstream oss;
        oss << "***ERR*** MOERTEL::Interface::ProjectNodes_MastertoSlave_NormalField:\n"
             << "***ERR*** Overflow in communication buffer occured\n"
             << "***ERR*** file/line: " << __FILE__ << "/" << __LINE__ << "\n";
		throw ReportError(oss);
      }
    }
    lComm()->Broadcast(&blength,1,proc);
    lComm()->Broadcast(&bcast[0],blength,proc);
    if (proc!=lComm()->MyPID())
    {
      int i;
      for (i=0; i<blength;)
      {
        int     nid = (int)bcast[i];  ++i;
        double  sid =      bcast[i];  ++i;
        double* xi  =      &bcast[i]; ++i; ++i; 
        double* n   =      &bcast[i]; ++i; ++i; ++i;
		double  gap =      bcast[i];  ++i;
		Teuchos::RCP<MOERTEL::Node> mnode = GetNodeView(nid);
		Teuchos::RCP<MOERTEL::Segment> seg = Teuchos::null;
        if (sid != -0.1)
          seg = GetSegmentView((int)sid);
        if (mnode == Teuchos::null)
        {
		  std::stringstream oss;
          oss << "***ERR*** MOERTEL::Interface::ProjectNodes_MastertoSlave_NormalField:\n"
               << "***ERR*** Cannot get view of node\n"
               << "***ERR*** file/line: " << __FILE__ << "/" << __LINE__ << "\n";
			throw ReportError(oss);
        }
        mnode->SetN(n);
        MOERTEL::ProjectedNode* pnode = new MOERTEL::ProjectedNode(*mnode,xi,seg.get());
        mnode->SetProjectedNode(pnode);
		mnode->SetGap(gap);
      }
      if (i != blength)
      {
		  std::stringstream oss;
        oss << "***ERR*** MOERTEL::Interface::ProjectNodes_MastertoSlave_NormalField:\n"
             << "***ERR*** Mismatch in dimension of recv buffer\n"
             << "***ERR*** file/line: " << __FILE__ << "/" << __LINE__ << "\n";
		throw ReportError(oss);
      }
    }
  } // for (int proc=0; proc<lComm()->NumProc(); ++proc)
  bcast.clear();

  return true;
}
コード例 #4
0
ファイル: mrtr_projector.cpp プロジェクト: 00liujj/trilinos
/*----------------------------------------------------------------------*
 |                                                           mwgee 07/05|
 |    modded by gah 07/2010                                             |
 *----------------------------------------------------------------------*/
bool MOERTEL::Projector::ProjectNodetoSegment_NodalNormal(MOERTEL::Node& node,
                 MOERTEL::Segment& seg, double xi[], double &gap)
{
  bool ok = true;
  // 2D version of the problem
  if (IsTwoDimensional())
  {
#if 0
    std::cout << "----- Projector: Node " << node.Id() << " Segment " << seg.Id() << std::endl;
    std::cout << "Segment\n" << seg;
    MOERTEL::Node** nodes = seg.Nodes();
    std::cout << *nodes[0];
    std::cout << *nodes[1];
#endif
    // we do a newton iteration for the projection coordinates xi
    // set starting value to the middle of the segment
    double eta = 0.0;
    int    i = 0;
    double F=0.0,dF=0.0,deta=0.0;
    for (i=0; i<10; ++i)
    {
      F    = evaluate_F_2D_NodalNormal(node,seg,eta,gap);
      if (abs(F) < 1.0e-10) break;
      dF   = evaluate_gradF_2D_NodalNormal(node,seg,eta);
      deta = (-F)/dF;
      eta += deta;
    }
    if (abs(F)>1.0e-9)
    {
      ok = false;
      if (OutLevel()>3)
      std::cout << "MOERTEL: ***WRN*** MOERTEL::Projector::ProjectNodetoSegment_NodalNormal:\n"
      	   << "MOERTEL: ***WRN*** Newton iteration failed to converge\n"
      	   << "MOERTEL: ***WRN*** #iterations = " << i << std::endl
      	   << "MOERTEL: ***WRN*** F(eta) = " << F << " gradF(eta) = " 
		   << dF << " eta = " << eta << " delta(eta) = " << deta << "\n"
           << "MOERTEL: ***WRN*** file/line: " << __FILE__ << "/" << __LINE__ << "\n";
    }
#if 0
    std::cout << "#iterations = " << i << " F = " << F << " eta = " << eta << std::endl;
#endif
    xi[0] = eta;
    return ok;
  }
  // 3D version of the problem
  else
  {
#if 0
    std::cout << "----- Projector: Node " << node.Id() << " Segment " << seg.Id() << std::endl;
    std::cout << "Segment " << seg;
    MOERTEL::Node** nodes = seg.Nodes();
    std::cout << *nodes[0];
    std::cout << *nodes[1];
    std::cout << *nodes[2];
#endif
    // we do a newton iteration for the projection coordinates xi
    // set starting value to the middle of the segment
    double eta[2]; 
    if (seg.Nnode()==3)
      eta[0] = eta[1] = 1./3.;
    else
      eta[0] = eta[1] = 0.;
    double alpha = 0.0;
    int    i=0;
    double F[3], dF[3][3], deta[3];
    double eps;
    for (i=0; i<30; ++i)
    {
      evaluate_FgradF_3D_NodalNormal(F,dF,node,seg,eta,alpha,gap);
      eps = MOERTEL::dot(F,F,3);
      if (eps < 1.0e-10) break;
      // std::cout << eps << std::endl;
      MOERTEL::solve33(dF,deta,F);
      eta[0] -= deta[0];
      eta[1] -= deta[1];
      alpha  -= deta[2];      
    }    
    if (eps>1.0e-10)
    {
      ok = false;
      if (OutLevel()>3)
      std::cout << "MOERTEL: ***WRN*** MOERTEL::Projector::ProjectNodetoSegment_NodalNormal:\n"
      	   << "MOERTEL: ***WRN*** 3D Newton iteration failed to converge\n"
      	   << "MOERTEL: ***WRN*** #iterations = " << i << std::endl
      	   << "MOERTEL: ***WRN*** eps = " << eps << " eta[3] = " << eta[0] << "/" << eta[1] << "/" << alpha << "\n"
           << "MOERTEL: ***WRN*** file/line: " << __FILE__ << "/" << __LINE__ << "\n";
    }
#if 0
    if (i>10)
      std::cout << "#iterations = " << i << " eps = " << eps << " eta = " << eta[0] << "/" << eta[1] << std::endl;
#endif
    xi[0] = eta[0];
    xi[1] = eta[1];
  } // 
  return ok;
}
コード例 #5
0
ファイル: mrtr_projector.cpp プロジェクト: 00liujj/trilinos
/*----------------------------------------------------------------------*
 |                                                           mwgee 07/05|
 | 2D case:                                                             |
 | this method evaluates the function                                   |
 | gradF(eta) =                                                         |
 |   ( Ni,eta * xis ) * ( Nj nyjs )                                     |
 | + ( Ni * xis - xm ) * ( Nj,eta * nyjs)                               |
 | - ( Ni,eta * yis ) * ( Nj nxjs )                                     |
 | - ( Ni * yis - ym ) * ( Nj,eta * nxjs)                               |
 | with Ni,eta derivative of shape functions of segment                 |
 |      Ni,Nj shape functions of segment                                |
 |      xis,yis nodal coords of segment's nodes i (slave side)          |
 |      xm,ym   nodal coords of master node                             |
 |      nxjs,nyjs outward normals of node j (slave side)                |
 *----------------------------------------------------------------------*/
double MOERTEL::Projector::evaluate_gradF_2D_SegmentNormal(MOERTEL::Node& node,
                                                        MOERTEL::Segment& seg, 
                                                        double eta)
{
  // check the type of function on the segment
  // Here, we need 1D functions set as function id 0
  MOERTEL::Function::FunctionType type = seg.FunctionType(0);
  if (type != MOERTEL::Function::func_Linear1D)
  {
	  std::stringstream oss;
    oss << "***ERR*** MOERTEL::Projector::evaluate_gradF_2D_SegmentNormal:\n"
    	 << "***ERR*** function is of wrong type\n"
    	 << "***ERR*** file/line: " << __FILE__ << "/" << __LINE__ << "\n";
	throw ReportError(oss);
  }
  
  // evaluate function and derivatives of the first function set on segment at eta
  int nsnode = seg.Nnode();
  double val[100];  
  double deriv[200];
  seg.EvaluateFunction(0,&eta,val,nsnode,deriv);
  
  // several intermediate data:
  // Nx     = Ni * xi
  // Nxeta  = Ni,eta * xi
  // NN     = Nj * nj
  // NNeta  = Nj,eta * nj
  
  // get nodal coords and normals of nodes and interpolate them
  double Nx[2];     Nx[0] = Nx[1] = 0.0;
  double Nxeta[2];  Nxeta[0] = Nxeta[1] = 0.0;
  double NN[2];     NN[0] = NN[1] = 0.0;
  double NNeta[2];  NNeta[0] = NNeta[1] = 0.0;
  MOERTEL::Node** snodes = seg.Nodes();
  if (!snodes)
  {
	  std::stringstream oss;
    oss << "***ERR*** MOERTEL::Projector::evaluate_gradF_2D_SegmentNormal:\n"
    	 << "***ERR*** segment " << seg.Id() << " ptr to it's nodes is zero\n"
    	 << "***ERR*** file/line: " << __FILE__ << "/" << __LINE__ << "\n";
	throw ReportError(oss);
  }
  for (int i=0; i<nsnode; ++i)
  {
    const double* X = snodes[i]->X();
    Nx[0]    += val[i]*X[0];
    Nx[1]    += val[i]*X[1];
    Nxeta[0] += deriv[i]*X[0];
    Nxeta[1] += deriv[i]*X[1];
    const double* N = snodes[i]->N();
    NN[0]    += val[i]*N[0];
    NN[1]    += val[i]*N[1];
    NNeta[0] += deriv[i]*N[0];
    NNeta[1] += deriv[i]*N[1];
  }
  
  // get master node coords
  const double* xm = node.X();
  
  // calculate gradF
  double gradF =   Nxeta[0]*NN[1] + (Nx[0] - xm[0])*NNeta[1]  
                 - Nxeta[1]*NN[0] - (Nx[1] - xm[1])*NNeta[0];
  return gradF;
}
コード例 #6
0
ファイル: mrtr_projector.cpp プロジェクト: 00liujj/trilinos
/*----------------------------------------------------------------------*
 |                                                           mwgee 07/05|
 |                                                   modded gah 07/2010 |
 | 2D case:                                                             |
 | this function evaluates the function                                 |
 | F(eta) = ( Ni * xim - xs ) cross ns ,                                |
 | with Ni shape functions of segment                                   |
 |      xim nodal coords of segment's nodes (master side)               |
 |      xs  nodal coords of node (slave side)                           |
 |      ns  outward normal of node (slave side)                         |
 *----------------------------------------------------------------------*/
double MOERTEL::Projector::evaluate_F_2D_NodalNormal(MOERTEL::Node& node,
          MOERTEL::Segment& seg, double eta, double &gap)
{
  // check the type of function on the segment
  // Here, we need 1D functions set as function id 0
  MOERTEL::Function::FunctionType type = seg.FunctionType(0);
  if (type != MOERTEL::Function::func_Linear1D)
  {
	  std::stringstream oss;
    oss << "***ERR*** MOERTEL::Projector::evaluate_F_2D_NodalNormal:\n"
    	 << "***ERR*** function is of wrong type\n"
    	 << "***ERR*** file/line: " << __FILE__ << "/" << __LINE__ << "\n";
	throw ReportError(oss);
  }
  
  // evaluate the first function set on segment at eta
  int nmnode = seg.Nnode();
  double val[100];
  seg.EvaluateFunction(0,&eta,val,nmnode,NULL);
  
  // get nodal coords of nodes and interpolate them
  double Nx[2]; 
  Nx[0] = Nx[1] = 0.0;
  MOERTEL::Node** mnodes = seg.Nodes();
  if (!mnodes)
  {
	  std::stringstream oss;
    oss << "***ERR*** MOERTEL::Projector::evaluate_F_2D_NodalNormal:\n"
    	 << "***ERR*** segment " << seg.Id() << " ptr to it's nodes is zero\n"
    	 << "***ERR*** file/line: " << __FILE__ << "/" << __LINE__ << "\n";
	throw ReportError(oss);
  }

  // Here, Nx[0] and Nx[1] are the coordinates of the guess at the root
  
  for (int i=0; i<nmnode; ++i)
  {
    const double* X = mnodes[i]->X();
    Nx[0] += val[i]*X[0];
    Nx[1] += val[i]*X[1];
  }
  
  // subtract xs (Coordinates of the slave node)
  const double* X = node.X();
  Nx[0] -= X[0];
  Nx[1] -= X[1];

  // get the normal of node
  const double* n = node.N();
  
  // calculate F
  double F = Nx[0]*n[1] - Nx[1]*n[0];

  gap = Nx[0] * n[0] + Nx[1] * n[1];

  // Do we need to divide by the length of the normal???  GAH
  //
//  gap = (Nx[0] * n[0] + Nx[1] * n[1])
//		  / sqrt(n[0] * n[0] + n[1] * n[1]);  // ||gap|| cos theta
#if 0
  std::cout << "node " << node.Id() << " seg " << seg.Id() << " n[0] " << n[0] << " n[1] " << n[1] << std::endl;
  std::cout << "X[0] " << X[0] << " X[1] " << X[1] << std::endl;
  std::cout << "Nx[0] " << Nx[0] << " Nx[1] " << Nx[1] << " gap " << gap << std::endl;
  std::cout << "norm " << sqrt(n[0] * n[0] + n[1] * n[1]) << std::endl;
#endif
  
  return F;
}