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

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

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

    Copyright (C) 2015

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

NAMESPACE_BEGIN(Grid);  

///////////////////////////////////////
// Two flavour ratio
///////////////////////////////////////
template<class Impl>
class TwoFlavourEvenOddRatioPseudoFermionAction : public Action<typename Impl::GaugeField> {
public:
  INHERIT_IMPL_TYPES(Impl);

private:
  FermionOperator<Impl> & NumOp;// the basic operator
  FermionOperator<Impl> & DenOp;// the basic operator

  OperatorFunction<FermionField> &DerivativeSolver;
  OperatorFunction<FermionField> &ActionSolver;

  FermionField PhiOdd;   // the pseudo fermion field for this trajectory
  FermionField PhiEven;  // the pseudo fermion field for this trajectory

public:
  TwoFlavourEvenOddRatioPseudoFermionAction(FermionOperator<Impl>  &_NumOp, 
					    FermionOperator<Impl>  &_DenOp, 
					    OperatorFunction<FermionField> & DS,
					    OperatorFunction<FermionField> & AS) :
    NumOp(_NumOp), 
    DenOp(_DenOp), 
    DerivativeSolver(DS), 
    ActionSolver(AS),
    PhiEven(_NumOp.FermionRedBlackGrid()),
    PhiOdd(_NumOp.FermionRedBlackGrid()) 
  {
    conformable(_NumOp.FermionGrid(), _DenOp.FermionGrid());
    conformable(_NumOp.FermionRedBlackGrid(), _DenOp.FermionRedBlackGrid());
    conformable(_NumOp.GaugeGrid(), _DenOp.GaugeGrid());
    conformable(_NumOp.GaugeRedBlackGrid(), _DenOp.GaugeRedBlackGrid());
  };

  virtual std::string action_name(){return "TwoFlavourEvenOddRatioPseudoFermionAction";}

  virtual std::string LogParameters(){
    std::stringstream sstream;
    sstream << GridLogMessage << "["<<action_name()<<"] has no parameters" << std::endl;
    return sstream.str();
  } 

      
  virtual void refresh(const GaugeField &U, GridParallelRNG& pRNG) {

    // P(phi) = e^{- phi^dag Vpc (MpcdagMpc)^-1 Vpcdag phi}
    //
    // NumOp == V
    // DenOp == M
    //
    // Take phi_o = Vpcdag^{-1} Mpcdag eta_o  ; eta_o = Mpcdag^{-1} Vpcdag Phi
    //
    // P(eta_o) = e^{- eta_o^dag eta_o}
    //
    // e^{x^2/2 sig^2} => sig^2 = 0.5.
    // 
    RealD scale = std::sqrt(0.5);

    FermionField eta    (NumOp.FermionGrid());
    FermionField etaOdd (NumOp.FermionRedBlackGrid());
    FermionField etaEven(NumOp.FermionRedBlackGrid());
    FermionField tmp    (NumOp.FermionRedBlackGrid());

    gaussian(pRNG,eta);

    pickCheckerboard(Even,etaEven,eta);
    pickCheckerboard(Odd,etaOdd,eta);

    NumOp.ImportGauge(U);
    DenOp.ImportGauge(U);

    SchurDifferentiableOperator<Impl> Mpc(DenOp);
    SchurDifferentiableOperator<Impl> Vpc(NumOp);

    // Odd det factors
    Mpc.MpcDag(etaOdd,PhiOdd);
    tmp=zero;
    ActionSolver(Vpc,PhiOdd,tmp);
    Vpc.Mpc(tmp,PhiOdd);            

    // Even det factors
    DenOp.MooeeDag(etaEven,tmp);
    NumOp.MooeeInvDag(tmp,PhiEven);

    PhiOdd =PhiOdd*scale;
    PhiEven=PhiEven*scale;
        
  };

  //////////////////////////////////////////////////////
  // S = phi^dag V (Mdag M)^-1 Vdag phi
  //////////////////////////////////////////////////////
  virtual RealD S(const GaugeField &U) {

    NumOp.ImportGauge(U);
    DenOp.ImportGauge(U);

    SchurDifferentiableOperator<Impl> Mpc(DenOp);
    SchurDifferentiableOperator<Impl> Vpc(NumOp);

    FermionField X(NumOp.FermionRedBlackGrid());
    FermionField Y(NumOp.FermionRedBlackGrid());

    Vpc.MpcDag(PhiOdd,Y);           // Y= Vdag phi
    X=zero;
    ActionSolver(Mpc,Y,X);          // X= (MdagM)^-1 Vdag phi
    //Mpc.Mpc(X,Y);                   // Y=  Mdag^-1 Vdag phi
    // Multiply by Ydag
    RealD action = real(innerProduct(Y,X));

    //RealD action = norm2(Y);

    // The EE factorised block; normally can replace with zero if det is constant (gauge field indept)
    // Only really clover term that creates this. Leave the EE portion as a future to do to make most
    // rapid progresss on DWF for now.
    //
    NumOp.MooeeDag(PhiEven,X);
    DenOp.MooeeInvDag(X,Y);
    action = action + norm2(Y);

    return action;
  };

  //////////////////////////////////////////////////////
  // dS/du = phi^dag dV (Mdag M)^-1 V^dag  phi
  //       - phi^dag V (Mdag M)^-1 [ Mdag dM + dMdag M ]  (Mdag M)^-1 V^dag  phi
  //       + phi^dag V (Mdag M)^-1 dV^dag  phi
  //////////////////////////////////////////////////////
  virtual void deriv(const GaugeField &U,GaugeField & dSdU) {

    NumOp.ImportGauge(U);
    DenOp.ImportGauge(U);

    SchurDifferentiableOperator<Impl> Mpc(DenOp);
    SchurDifferentiableOperator<Impl> Vpc(NumOp);

    FermionField  X(NumOp.FermionRedBlackGrid());
    FermionField  Y(NumOp.FermionRedBlackGrid());

    // This assignment is necessary to be compliant with the HMC grids
    GaugeField force(dSdU._grid);

    //Y=Vdag phi
    //X = (Mdag M)^-1 V^dag phi
    //Y = (Mdag)^-1 V^dag  phi
    Vpc.MpcDag(PhiOdd,Y);          // Y= Vdag phi
    X=zero;
    DerivativeSolver(Mpc,Y,X);     // X= (MdagM)^-1 Vdag phi
    Mpc.Mpc(X,Y);                  // Y=  Mdag^-1 Vdag phi

    // phi^dag V (Mdag M)^-1 dV^dag  phi
    Vpc.MpcDagDeriv(force , X, PhiOdd );   dSdU = force;
  
    // phi^dag dV (Mdag M)^-1 V^dag  phi
    Vpc.MpcDeriv(force , PhiOdd, X );      dSdU = dSdU+force;

    //    -    phi^dag V (Mdag M)^-1 Mdag dM   (Mdag M)^-1 V^dag  phi
    //    -    phi^dag V (Mdag M)^-1 dMdag M   (Mdag M)^-1 V^dag  phi
    Mpc.MpcDeriv(force,Y,X);              dSdU = dSdU-force;
    Mpc.MpcDagDeriv(force,X,Y);           dSdU = dSdU-force;

    // FIXME No force contribution from EvenEven assumed here
    // Needs a fix for clover.
    assert(NumOp.ConstEE() == 1);
    assert(DenOp.ConstEE() == 1);

    dSdU = -dSdU;
        
  };
};

NAMESPACE_END(Grid);

#endif