includeLinks/DistanceFromTarget.hpp

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/* ***************************************************************** 
    MESQUITE -- The Mesh Quality Improvement Toolkit

    Copyright 2004 Sandia Corporation and Argonne National
    Laboratory.  Under the terms of Contract DE-AC04-94AL85000 
    with Sandia Corporation, the U.S. Government retains certain 
    rights in this software.

    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 
    (lgpl.txt) along with this library; if not, write to the Free Software
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 
    diachin2@llnl.gov, djmelan@sandia.gov, mbrewer@sandia.gov, 
    pknupp@sandia.gov, tleurent@mcs.anl.gov, tmunson@mcs.anl.gov      
   
  ***************************************************************** */

#ifndef DistanceFromTarget_hpp
#define DistanceFromTarget_hpp

#include "Mesquite.hpp"
#include "MsqError.hpp"
#include "PatchData.hpp"
#include "QualityMetric.hpp"
#include "TargetMatrix.hpp"

namespace Mesquite
{
  
  class DistanceFromTarget : public QualityMetric
  {
  public:
    
    virtual ~DistanceFromTarget()
       {};

  protected:
    void compute_T_matrices(MsqMeshEntity &elem, PatchData& pd,
                           Matrix3D T[], size_t num_T, double c_k[], MsqError &err);
 
    bool get_barrier_function(PatchData& pd, const double &tau, double &h, MsqError &err);

  private:
    
  };

  
  inline void DistanceFromTarget::compute_T_matrices(MsqMeshEntity &elem, PatchData& pd,
                        Matrix3D T[], size_t num_T, double c_k[], MsqError &err)
  {    
      // Gets the element corner matrices.
    elem.compute_corner_matrices(pd, T, num_T, err);

//     for (size_t i=0; i<num_T; ++i)
//       std::cout << "A["<<i<<"]:\n" << T[i] << std::endl;

    int elem_idx = pd.get_element_index(&elem);
    const TargetMatrix* W = pd.targetMatrices.get_element_corner_tags(&pd, elem_idx, err );
    
//     for (size_t i=0; i<num_T; ++i)
//       std::cout << "W["<<i<<"]:\n" << W[i] << std::endl;

    for (size_t i=0; i<num_T; ++i) {
      timesInvA(T[i], W[i]);
      c_k[i] = W[i].get_cK();
    }
  }


  inline bool DistanceFromTarget::get_barrier_function(PatchData& pd, const double &tau, double &h, MsqError &err)
  { 

     double delta=pd.get_barrier_delta(err);  MSQ_ERRZERO(err);

     // Note: technically, we want delta=eta*tau-max
     //       whereas the function above gives delta=eta*alpha-max
     //      
     //       Because the only requirement on eta is eta << 1,
     //       and because tau-max = alpha-max/0.707 we can
     //       ignore the discrepancy

     if (delta==0) { 
        if (tau < MSQ_DBL_MIN ) {
           return false;
        }
        else {
           h=tau;
        }

     // Note: when delta=0, the vertex_barrier_function
     //       formally gives h=tau as well.
     //       We just do it this way to avoid any 
     //       roundoff issues.
     // Also: when delta=0, this metric is identical
     //       to the original condition number with
     //       the barrier at tau=0

     }
     else {
        h = 0.5*(tau+sqrt(tau*tau+4*delta*delta));

        if (h<MSQ_DBL_MIN && fabs(tau) > MSQ_DBL_MIN ) { 
          h = delta*delta/fabs(tau); }
 
        // Note: Analytically, h is strictly positive, but
        //       it can be zero numerically if tau
        //       is a large negative number 
        //       In the h=0 case, we use a different analytic
        //       approximation to compute h.
     }
     if (h<MSQ_DBL_MIN) {
       MSQ_SETERR(err)("Barrier function is zero due to excessively large "
                       "negative area compared to delta.\nTry to untangle "
                       "mesh another way.", MsqError::INVALID_MESH);
       return false;
     }
     return true;
  }  
  
} //namespace


#endif // DistanceFromTarget_hpp