IdealWeightInverseMeanRatio.hpp

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    MESQUITE -- The Mesh Quality Improvement Toolkit

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    Laboratory.  Under the terms of Contract DE-AC04-94AL85000
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// -*- Mode : c++; tab-width: 3; c-tab-always-indent: t; indent-tabs-mode: nil; c-basic-offset: 3
// -*-

/*! \file IdealWeightInverseMeanRatio.hpp

Header file for the MBMesquite::IdealWeightInverseMeanRatio class

\author Michael Brewer
\author Thomas Leurent
\date   2002-06-19
 */

#ifndef IdealWeightInverseMeanRatio_hpp
#define IdealWeightInverseMeanRatio_hpp

#include "Mesquite.hpp"
#include "ElementQM.hpp"
#include "AveragingQM.hpp"
#include "Vector3D.hpp"
#include "Matrix3D.hpp"
#include "Exponent.hpp"

namespace MBMesquite
{
class MsqMeshEntity;
class PatchData;
class MsqError;

/*! \class IdealWeightInverseMeanRatio
  \brief Computes the inverse mean ratio of given element.

  The metric does not use the sample point functionality or the
  compute_weighted_jacobian.  It evaluates the metric at
  the element vertices, and uses the isotropic ideal element.
  Optionally, the metric computation can be raised to the
  'pow_dbl' power.  This does not necessarily raise the metric
  value to the 'pow_dbl' power but instead raises each local
  metric.  For example, if the corner inverse mean ratios of a quadraliteral
  element were m1,m2,m3, and m4 and we set pow_dbl=2 and
  used linear averaging, the metric value would then be
  m = .25(m1*m1 + m2*m2 + m3*m3 + m4*m4).  The metric does
  require a feasible region, and the metric needs to be minimized
  if pow_dbl is greater than zero and maximized if pow_dbl
  is less than zero.  pow_dbl being equal to zero is invalid.
*/
class IdealWeightInverseMeanRatio : public ElementQM, public AveragingQM
{
  public:
    MESQUITE_EXPORT IdealWeightInverseMeanRatio( MsqError& err, double power = 1.0 );
    MESQUITE_EXPORT IdealWeightInverseMeanRatio();

    //! virtual destructor ensures use of polymorphism during destruction
    MESQUITE_EXPORT virtual ~IdealWeightInverseMeanRatio() {}

    virtual std::string get_name() const;

    //! 1 if metric should be minimized, -1 if metric should be maximized.
    virtual int get_negate_flag() const;

    virtual bool evaluate( PatchData& pd, size_t handle, double& value, MsqError& err );

    virtual bool evaluate_with_gradient( PatchData& pd,
                                         size_t handle,
                                         double& value,
                                         std::vector< size_t >& indices,
                                         std::vector< Vector3D >& gradient,
                                         MsqError& err );

    virtual bool evaluate_with_Hessian_diagonal( PatchData& pd,
                                                 size_t handle,
                                                 double& value,
                                                 std::vector< size_t >& indices,
                                                 std::vector< Vector3D >& gradient,
                                                 std::vector< SymMatrix3D >& Hessian,
                                                 MsqError& err );

    virtual bool evaluate_with_Hessian( PatchData& pd,
                                        size_t handle,
                                        double& value,
                                        std::vector< size_t >& indices,
                                        std::vector< Vector3D >& gradient,
                                        std::vector< Matrix3D >& Hessian,
                                        MsqError& err );

  private:
    //! Sets the power value in the metric computation.
    void set_metric_power( double pow_dbl, MsqError& err );

    // arrays used in Hessian computations
    // We allocate them here, so that one allocation only is done.
    // This gives a big computation speed increase.
    Vector3D mCoords[4];      // Vertex coordinates for the (decomposed) elements
    Vector3D mGradients[32];  // Gradient of metric with respect to the coords
    Matrix3D mHessians[80];   // Hessian of metric with respect to the coords
    double mMetrics[8];       // Metric values for the (decomposed) elements
                              // variables used in the definition of the metric (2d and 3d)
    double a2Con;
    Exponent b2Con;
    Exponent c2Con;

    double a3Con;
    Exponent b3Con;
    Exponent c3Con;
};
}  // namespace MBMesquite

#endif  // IdealWeightInverseMeanRatio_hpp