cmtkEigenSystemSymmetricMatrix3x3.h

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/*
//
//  Copyright 1997-2009 Torsten Rohlfing
//
//  Copyright 2004-2010 SRI International
//
//  This file is part of the Computational Morphometry Toolkit.
//
//  http://www.nitrc.org/projects/cmtk/
//
//  The Computational Morphometry Toolkit is free software: you can
//  redistribute it and/or modify it under the terms of the GNU General Public
//  License as published by the Free Software Foundation, either version 3 of
//  the License, or (at your option) any later version.
//
//  The Computational Morphometry Toolkit 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 General Public License for more details.
//
//  You should have received a copy of the GNU General Public License along
//  with the Computational Morphometry Toolkit.  If not, see
//  <http://www.gnu.org/licenses/>.
//
//  $Revision: 2398 $
//
//  $LastChangedDate: 2010-10-05 14:54:37 -0700 (Tue, 05 Oct 2010) $
//
//  $LastChangedBy: torstenrohlfing $
//
*/

#ifndef __cmtkEigenSystemSymmetricMatrix3x3_h_included_
#define __cmtkEigenSystemSymmetricMatrix3x3_h_included_

#include <cmtkconfig.h>

#include <Base/cmtkMatrix3x3.h>
#include <Base/cmtkFixedVector.h>

namespace
cmtk
{

template<class TFloat>
class EigenSystemSymmetricMatrix3x3
{
public:
  EigenSystemSymmetricMatrix3x3( const Matrix3x3<TFloat>& matrix, 
                                 const bool sortAbsolute = true  );
  
  const FixedVector<3,TFloat> GetNthEigenvector( const size_t n ) const
  {
    return FixedVector<3,TFloat>( this->m_Eigenvectors[n] );
  }
  
  TFloat GetNthEigenvalue( const size_t n ) const
  {
    return this->m_Eigenvalues[n];
  }

protected:
  TFloat m_Eigenvectors[3][3];

  TFloat m_Eigenvalues[3];

private:
  static TFloat hypot2( const TFloat& x, const TFloat& y);

  static void tred2(TFloat V[3][3], TFloat d[3], TFloat e[3]);

  /* Symmetric tridiagonal QL algorithm.
   */
  static void tql2(TFloat V[3][3], TFloat d[3], TFloat e[3], const bool sortAbsolute = true );
};


} // namespace cmtk

#include "cmtkEigenSystemSymmetricMatrix3x3.txx"

#endif // #ifndef __cmtkEigenSystemSymmetricMatrix3x3_h_included_