include/ewalena/lac/solver_quadratic.h

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// -------------------------------------------------------------------
// @author Toby D. Young
// @version $Id: solver_quadratic.h 987 2012-11-26 15:16:27Z oneliefleft $
//
// Copyright 2012 namespace ewalena authors. All rights reserved.
//
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// modification, are permitted provided that the following conditions
// are met:
//
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above
//    copyright notice, this list of conditions and the following
//    disclaimer in the documentation and/or other materials provided
//    with the distribution.
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#ifndef __ewalena_solver_quadratic_h
#define __ewalena_solver_quadratic_h

#ifdef EWALENA_HAVE_CONFIG_H
#include <ewalena/base/config.h>
#endif

#include <ewalena/lac/solver_base.h>

#include <algorithm>

namespace ewalena 
{

  template <typename ValueType = double>
    class SolverQuadratic
    : 
    public SolverBase<ValueType>
    {
      
    public:

    SolverQuadratic (SolverControl<ValueType> &solver_control = 0);
    
    virtual void solve (const Matrix<ValueType> &A,
                        Vector<ValueType>       &lambda,
                        VectorBasis<ValueType>  &x);
    
    protected:
    
    ValueType trace (const Matrix<ValueType> &matrix);
    
    ValueType det (const Matrix<ValueType> &matrix);


    }; /* SolverJacobi */
  
  /*-------------- Inline and Other Functions -----------------------*/
  
  template <typename ValueType>
    inline
    ValueType
    SolverQuadratic<ValueType>::trace (const Matrix<ValueType> &matrix)
    {
      assert (matrix.n_cols () == matrix.n_rows ());

      ValueType trace = ValueType (0);

      for (unsigned int i=0; i<matrix.n_rows (); ++i)
        trace += matrix(i,i);
        
      return trace;
    }


  template <typename ValueType>
    inline
    ValueType
    SolverQuadratic<ValueType>::det (const Matrix<ValueType> &matrix)
    {
      assert (matrix.n_cols () == matrix.n_rows ());

      switch (matrix.n_rows ())
        {
        case 2:
          return 
            matrix(1,1) * matrix(2,2) - 
            matrix(1,2) * matrix(2,1);
          break;

        case 3:
          return 
            matrix(1,1) * matrix(2,2) * matrix(3,3) +
            matrix(2,1) * matrix(3,2) * matrix(1,3) +
            matrix(3,1) * matrix(1,2) * matrix(2,3) -
            matrix(3,1) * matrix(2,2) * matrix(1,3) -
            matrix(2,1) * matrix(1,2) * matrix(3,3) -
            matrix(1,1) * matrix(3,2) * matrix(2,3);
          break;

        default:
          assert (false);
        }

    }

} /* namespace ewalena */

#endif /* __ewalena_solver_quadratic_h */