Grid/lib/algorithms/iterative/NormalEquations.h

    /*************************************************************************************

    Grid physics library, www.github.com/paboyle/Grid 

    Source file: ./lib/algorithms/iterative/NormalEquations.h

    Copyright (C) 2015

Author: Peter Boyle <paboyle@ph.ed.ac.uk>

    This program 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 2 of the License, or
    (at your option) any later version.

    This program 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 this program; if not, write to the Free Software Foundation, Inc.,
    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

    See the full license in the file "LICENSE" in the top level distribution directory
    *************************************************************************************/
    /*  END LEGAL */
#ifndef GRID_NORMAL_EQUATIONS_H
#define GRID_NORMAL_EQUATIONS_H

namespace Grid {

  ///////////////////////////////////////////////////////////////////////////////////////////////////////
  // Take a matrix and form an NE solver calling a Herm solver
  ///////////////////////////////////////////////////////////////////////////////////////////////////////
  template<class Field> class NormalEquations : public OperatorFunction<Field>{
  private:
    SparseMatrixBase<Field> & _Matrix;
    OperatorFunction<Field> & _HermitianSolver;

  public:

    /////////////////////////////////////////////////////
    // Wrap the usual normal equations trick
    /////////////////////////////////////////////////////
  NormalEquations(SparseMatrixBase<Field> &Matrix, OperatorFunction<Field> &HermitianSolver) 
    :  _Matrix(Matrix), _HermitianSolver(HermitianSolver) {}; 

    void operator() (const Field &in, Field &out){
 
      Field src(in._grid);

      _Matrix.Mdag(in,src);
      _HermitianSolver(src,out);  // Mdag M out = Mdag in
 
    }     
  };

}
#endif