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

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

    Source file: ./lib/qcd/action/pseudofermion/EvenOddSchurDifferentiable.h

    Copyright (C) 2015

Author: Peter Boyle <paboyle@ph.ed.ac.uk>
Author: Guido Cossu <guido.cossu@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 QCD_EVEN_ODD_SCHUR_DIFFERENTIABLE_H
#define QCD_EVEN_ODD_SCHUR_DIFFERENTIABLE_H

NAMESPACE_BEGIN(Grid);  

// Base even odd HMC on the normal Mee based schur decomposition.
//
//     M = (Mee Meo) =  (1             0 )   (Mee   0               )  (1 Mee^{-1} Meo)
//         (Moe Moo)    (Moe Mee^-1    1 )   (0   Moo-Moe Mee^-1 Meo)  (0   1         )
//
// Determinant is det of middle factor
// This assumes Mee is indept of U.
//
template<class Impl>
class SchurDifferentiableOperator :  public SchurDiagMooeeOperator<FermionOperator<Impl>,typename Impl::FermionField> 
{
public:
  INHERIT_IMPL_TYPES(Impl);

  typedef FermionOperator<Impl> Matrix;

  SchurDifferentiableOperator (Matrix &Mat) : SchurDiagMooeeOperator<Matrix,FermionField>(Mat) {};

  void MpcDeriv(GaugeField &Force,const FermionField &U,const FermionField &V) {
        
    GridBase *fgrid   = this->_Mat.FermionGrid();
    GridBase *fcbgrid = this->_Mat.FermionRedBlackGrid();

    FermionField tmp1(fcbgrid);
    FermionField tmp2(fcbgrid);

    conformable(fcbgrid,U._grid);
    conformable(fcbgrid,V._grid);

    // Assert the checkerboard?? or code for either
    assert(U.Checkerboard()==Odd);
    assert(V.Checkerboard()==U.Checkerboard());

    // NOTE Guido: WE DO NOT WANT TO USE THE ucbgrid GRID FOR THE FORCE
    // it is not conformable with the HMC force field
    // Case: Ls vectorised fields
    // INHERIT FROM THE Force field instead
    GridRedBlackCartesian* forcecb = new GridRedBlackCartesian(Force._grid);
    GaugeField ForceO(forcecb);
    GaugeField ForceE(forcecb);


    //  X^dag Der_oe MeeInv Meo Y
    // Use Mooee as nontrivial but gauge field indept
    this->_Mat.Meooe   (V,tmp1);      // odd->even -- implicit -0.5 factor to be applied
    this->_Mat.MooeeInv(tmp1,tmp2);   // even->even 
    this->_Mat.MoeDeriv(ForceO,U,tmp2,DaggerNo);
    //  Accumulate X^dag M_oe MeeInv Der_eo Y
    this->_Mat.MeooeDag   (U,tmp1);    // even->odd -- implicit -0.5 factor to be applied
    this->_Mat.MooeeInvDag(tmp1,tmp2); // even->even 
    this->_Mat.MeoDeriv(ForceE,tmp2,V,DaggerNo);
          
    assert(ForceE.Checkerboard()==Even);
    assert(ForceO.Checkerboard()==Odd);

    setCheckerboard(Force,ForceE); 
    setCheckerboard(Force,ForceO);
    Force=-Force;

    delete forcecb;
  }


  void MpcDagDeriv(GaugeField &Force,const FermionField &U,const FermionField &V) {
        
    GridBase *fgrid   = this->_Mat.FermionGrid();
    GridBase *fcbgrid = this->_Mat.FermionRedBlackGrid();

    FermionField tmp1(fcbgrid);
    FermionField tmp2(fcbgrid);

    conformable(fcbgrid,U._grid);
    conformable(fcbgrid,V._grid);

    // Assert the checkerboard?? or code for either
    assert(V.Checkerboard()==Odd);
    assert(V.Checkerboard()==V.Checkerboard());

    // NOTE Guido: WE DO NOT WANT TO USE THE ucbgrid GRID FOR THE FORCE
    // it is not conformable with the HMC force field
    // INHERIT FROM THE Force field instead
    GridRedBlackCartesian* forcecb = new GridRedBlackCartesian(Force._grid);
    GaugeField ForceO(forcecb);
    GaugeField ForceE(forcecb);

    //  X^dag Der_oe MeeInv Meo Y
    // Use Mooee as nontrivial but gauge field indept
    this->_Mat.MeooeDag   (V,tmp1);      // odd->even -- implicit -0.5 factor to be applied
    this->_Mat.MooeeInvDag(tmp1,tmp2);   // even->even 
    this->_Mat.MoeDeriv(ForceO,U,tmp2,DaggerYes);
          
    //  Accumulate X^dag M_oe MeeInv Der_eo Y
    this->_Mat.Meooe   (U,tmp1);    // even->odd -- implicit -0.5 factor to be applied
    this->_Mat.MooeeInv(tmp1,tmp2); // even->even 
    this->_Mat.MeoDeriv(ForceE,tmp2,V,DaggerYes);

    assert(ForceE.Checkerboard()==Even);
    assert(ForceO.Checkerboard()==Odd);

    setCheckerboard(Force,ForceE); 
    setCheckerboard(Force,ForceO);
    Force=-Force;

    delete forcecb;
  }

};

NAMESPACE_END(Grid);

#endif