TwoFlavourEvenOdd.h

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/*************************************************************************************
 
Grid physics library, www.github.com/paboyle/Grid
 
Source file: ./lib/qcd/action/pseudofermion/TwoFlavourEvenOdd.h
 
Copyright (C) 2015
 
Author: Peter Boyle <pabobyle@ph.ed.ac.uk>
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 QCD_PSEUDOFERMION_TWO_FLAVOUR_EVEN_ODD_H
#define QCD_PSEUDOFERMION_TWO_FLAVOUR_EVEN_ODD_H
 
NAMESPACE_BEGIN(Grid);
  

// Two flavour pseudofermion action for any EO prec dop
template <class Impl>
class TwoFlavourEvenOddPseudoFermionAction
  : public Action<typename Impl::GaugeField> {
public:
  INHERIT_IMPL_TYPES(Impl);
 
private:
  FermionOperator<Impl> &FermOp;  // 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:
  // Pass in required objects.
  TwoFlavourEvenOddPseudoFermionAction(FermionOperator<Impl> &Op,
                       OperatorFunction<FermionField> &DS,
                       OperatorFunction<FermionField> &AS)
    : FermOp(Op),
      DerivativeSolver(DS),
      ActionSolver(AS),
      PhiEven(Op.FermionRedBlackGrid()),
      PhiOdd(Op.FermionRedBlackGrid())
  {};
  
  virtual std::string action_name(){return "TwoFlavourEvenOddPseudoFermionAction";}
      
  virtual std::string LogParameters(){
    std::stringstream sstream;
    sstream << GridLogMessage << "["<<action_name()<<"] has no parameters" << std::endl;
    return sstream.str();
  }  
 

  // Push the gauge field in to the dops. Assume any BC's and smearing already applied
  virtual void refresh(const GaugeField &U, GridSerialRNG &sRNG, GridParallelRNG& pRNG) {
    
    // P(phi) = e^{- phi^dag (MpcdagMpc)^-1 phi}
    // Phi = McpDag eta 
    // P(eta) = e^{- eta^dag eta}
    //
    // e^{x^2/2 sig^2} => sig^2 = 0.5.
    
    RealD scale = std::sqrt(0.5);
    
    FermionField eta    (FermOp.FermionGrid());
    FermionField etaOdd (FermOp.FermionRedBlackGrid());
    FermionField etaEven(FermOp.FermionRedBlackGrid());
    
    gaussian(pRNG,eta);
    pickCheckerboard(Even,etaEven,eta);
    pickCheckerboard(Odd,etaOdd,eta);
    
    FermOp.ImportGauge(U);
    SchurDifferentiableOperator<Impl> PCop(FermOp);
    
    
    PCop.MpcDag(etaOdd,PhiOdd);
    
    FermOp.MooeeDag(etaEven,PhiEven);
    
    PhiOdd =PhiOdd*scale;
    PhiEven=PhiEven*scale;
    
  };
  
  // S = phi^dag (Mdag M)^-1 phi  (odd)
  //   + phi^dag (Mdag M)^-1 phi  (even)
  virtual RealD S(const GaugeField &U) {
    
    FermOp.ImportGauge(U);
 
    FermionField X(FermOp.FermionRedBlackGrid());
    FermionField Y(FermOp.FermionRedBlackGrid());
    
    SchurDifferentiableOperator<Impl> PCop(FermOp);
 
    X=Zero();
    ActionSolver(PCop,PhiOdd,X);
    PCop.Op(X,Y);
    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.
    FermOp.MooeeInvDag(PhiEven,Y);
    action = action + norm2(Y);
 
    std::cout << GridLogMessage << "Pseudofermion EO action "<<action<<std::endl;
    return action;
  };

  //
  // dS/du = - phi^dag  (Mdag M)^-1 [ Mdag dM + dMdag M ]  (Mdag M)^-1 phi
  //       = - phi^dag M^-1 dM (MdagM)^-1 phi -  phi^dag (MdagM)^-1 dMdag dM (Mdag)^-1 phi 
  //
  //       = - Ydag dM X  - Xdag dMdag Y
  //
  virtual void deriv(const GaugeField &U,GaugeField & dSdU) {
    FermOp.ImportGauge(U);
 
    FermionField X(FermOp.FermionRedBlackGrid());
    FermionField Y(FermOp.FermionRedBlackGrid());
    GaugeField tmp(FermOp.GaugeGrid());
 
    SchurDifferentiableOperator<Impl> Mpc(FermOp);
 
    // Our conventions really make this UdSdU; We do not differentiate wrt Udag here.
    // So must take dSdU - adj(dSdU) and left multiply by mom to get dS/dt.
 
    X=Zero();
    DerivativeSolver(Mpc,PhiOdd,X);
    Mpc.Mpc(X,Y);
    Mpc.MpcDeriv(tmp , Y, X );    dSdU=tmp;
    Mpc.MpcDagDeriv(tmp , X, Y);  dSdU=dSdU+tmp;
 
    // Treat the EE case. (MdagM)^-1 = Minv Minvdag
    // Deriv defaults to zero.
    //        FermOp.MooeeInvDag(PhiOdd,Y);
    //      FermOp.MooeeInv(Y,X);
    //  FermOp.MeeDeriv(tmp , Y, X,DaggerNo );    dSdU=tmp;
    //  FermOp.MeeDeriv(tmp , X, Y,DaggerYes);  dSdU=dSdU+tmp;
 
    assert(FermOp.ConstEE() == 1);
 
    /*
      FermOp.MooeeInvDag(PhiOdd,Y);
      FermOp.MooeeInv(Y,X);
      FermOp.MeeDeriv(tmp , Y, X,DaggerNo );    dSdU=tmp;
      FermOp.MeeDeriv(tmp , X, Y,DaggerYes);  dSdU=dSdU+tmp;
    */
    
    //dSdU = Ta(dSdU);
 
  };
 
};
    
NAMESPACE_END(Grid);
 
#endif