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

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

    Source file: ./tests/Test_gpdwf_force.cc

    Copyright (C) 2015

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 */
#include <Grid/Grid.h>

using namespace std;
using namespace Grid;
 ;

 

int main (int argc, char ** argv)
{
  Grid_init(&argc,&argv);

  Coordinate latt_size   = GridDefaultLatt();
  Coordinate simd_layout = GridDefaultSimd(Nd,vComplex::Nsimd());
  Coordinate mpi_layout  = GridDefaultMpi();

  const int Ls=8;

  GridCartesian         * UGrid   = SpaceTimeGrid::makeFourDimGrid(GridDefaultLatt(), GridDefaultSimd(Nd,vComplex::Nsimd()),GridDefaultMpi());
  GridRedBlackCartesian * UrbGrid = SpaceTimeGrid::makeFourDimRedBlackGrid(UGrid);
  GridCartesian         * FGrid   = SpaceTimeGrid::makeFiveDimGrid(Ls,UGrid);
  GridRedBlackCartesian * FrbGrid = SpaceTimeGrid::makeFiveDimRedBlackGrid(Ls,UGrid);

  std::vector<int> seeds4({1,2,3,4});
  std::vector<int> seeds5({5,6,7,8});
  GridParallelRNG          RNG5(FGrid);  RNG5.SeedFixedIntegers(seeds5);
  GridParallelRNG          RNG4(UGrid);  RNG4.SeedFixedIntegers(seeds4);

  int threads = GridThread::GetThreads();
  std::cout<<GridLogMessage << "Grid is setup to use "<<threads<<" threads"<<std::endl;

  typedef typename GparityDomainWallFermionR::FermionField FermionField;
  FermionField phi        (FGrid); gaussian(RNG5,phi);
  FermionField Mphi       (FGrid); 
  FermionField MphiPrime  (FGrid); 

  LatticeGaugeField U(UGrid);

  SU3::HotConfiguration(RNG4,U);
  
  ////////////////////////////////////
  // Unmodified matrix element
  ////////////////////////////////////
  RealD mass=0.01; 
  RealD M5=1.8; 

  const int nu = 3;
  std::vector<int> twists(Nd,0);  twists[nu] = 1;
  GparityDomainWallFermionR::ImplParams params;  params.twists = twists;
  GparityDomainWallFermionR Ddwf(U,*FGrid,*FrbGrid,*UGrid,*UrbGrid,mass,M5,params);
  Ddwf.M   (phi,Mphi);

  ComplexD S    = innerProduct(Mphi,Mphi); // pdag MdagM p

  // get the deriv of phidag MdagM phi with respect to "U"
  LatticeGaugeField UdSdU(UGrid);
  LatticeGaugeField tmp(UGrid);

  Ddwf.MDeriv(tmp , Mphi,  phi,DaggerNo );  UdSdU=tmp;
  Ddwf.MDeriv(tmp , phi,  Mphi,DaggerYes ); UdSdU=(UdSdU+tmp);  
  
  FermionField Ftmp      (FGrid);

  ////////////////////////////////////
  // Modify the gauge field a little 
  ////////////////////////////////////
  RealD dt = 0.0001;

  LatticeColourMatrix mommu(UGrid); 
  LatticeColourMatrix forcemu(UGrid); 
  LatticeGaugeField mom(UGrid); 
  LatticeGaugeField Uprime(UGrid); 

  for(int mu=0;mu<Nd;mu++){

    SU3::GaussianFundamentalLieAlgebraMatrix(RNG4, mommu); // Traceless antihermitian momentum; gaussian in lie alg

    PokeIndex<LorentzIndex>(mom,mommu,mu);

    // fourth order exponential approx
    auto U_v = U.View();
    auto mom_v = mom.View();
    auto Uprime_v = Uprime.View();
    thread_loop( (auto i=mom_v.begin();i<mom_v.end();i++),{
      Uprime_v[i](mu) = U_v[i](mu)
	+ mom_v[i](mu)*U_v[i](mu)*dt 
	+ mom_v[i](mu) *mom_v[i](mu) *U_v[i](mu)*(dt*dt/2.0)
	+ mom_v[i](mu) *mom_v[i](mu) *mom_v[i](mu) *U_v[i](mu)*(dt*dt*dt/6.0)
	+ mom_v[i](mu) *mom_v[i](mu) *mom_v[i](mu) *mom_v[i](mu) *U_v[i](mu)*(dt*dt*dt*dt/24.0)
	+ mom_v[i](mu) *mom_v[i](mu) *mom_v[i](mu) *mom_v[i](mu) *mom_v[i](mu) *U_v[i](mu)*(dt*dt*dt*dt*dt/120.0)
	+ mom_v[i](mu) *mom_v[i](mu) *mom_v[i](mu) *mom_v[i](mu) *mom_v[i](mu) *mom_v[i](mu) *U_v[i](mu)*(dt*dt*dt*dt*dt*dt/720.0)
	;
    });
  }
  
  Ddwf.ImportGauge(Uprime);
  Ddwf.M          (phi,MphiPrime);

  ComplexD Sprime    = innerProduct(MphiPrime   ,MphiPrime);

  //////////////////////////////////////////////
  // Use derivative to estimate dS
  //////////////////////////////////////////////

  LatticeComplex dS(UGrid); dS = Zero();
  for(int mu=0;mu<Nd;mu++){
    mommu   = PeekIndex<LorentzIndex>(UdSdU,mu);
    mommu=Ta(mommu)*2.0;
    PokeIndex<LorentzIndex>(UdSdU,mommu,mu);
  }

  for(int mu=0;mu<Nd;mu++){
    forcemu = PeekIndex<LorentzIndex>(UdSdU,mu);
    mommu   = PeekIndex<LorentzIndex>(mom,mu);

    // Update PF action density
    dS = dS+trace(mommu*forcemu)*dt;
  }

  ComplexD dSpred    = sum(dS);

  // From TwoFlavourPseudoFermion:
  //////////////////////////////////////////////////////
  // 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
  //
  //////////////////////////////////////////////////////
  // 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.
  //
  //  When we have Gparity -- U and Uconj enter.
  //
  // dU/dt  = p U
  // dUc/dt = p* Uc     // Is p real, traceless, etc..
  //
  // dS/dt = dUdt dSdU = p U dSdU
  //
  // Gparity --- deriv is pc Uc dSdUc + p U dSdU 
  //
  //	Pmu = Zero();
  //	for(int mu=0;mu<Nd;mu++){
  //	  SU<Ncol>::GaussianFundamentalLieAlgebraMatrix(pRNG, Pmu);
  //	  PokeIndex<LorentzIndex>(P, Pmu, mu);
  //	}
  //
  //
  //    GridBase *grid = out.Grid();
  //    LatticeReal ca (grid);
  //    LatticeMatrix  la (grid);
  //    Complex ci(0.0,scale);
  //    Matrix ta;
  //    out=Zero();
  //    for(int a=0;a<generators();a++){
  //      gaussian(pRNG,ca); 
  //      generator(a,ta);
  //      la=toComplex(ca)*ci*ta;  // i t_a Lambda_a c_a // c_a is gaussian
  //      out += la; 
  //    }
  //  p = sum_a i gauss_a t_a 
  //
  // dU = p U dt
  //
  // dUc = p^c Uc dt = -i gauss_a t_a^c Uc 
  // 
  //
  // For Gparity the dS /dt from Uc links 
  // 

  std::cout << GridLogMessage << " S      "<<S<<std::endl;
  std::cout << GridLogMessage << " Sprime "<<Sprime<<std::endl;
  std::cout << GridLogMessage << "dS      "<<Sprime-S<<std::endl;
  std::cout << GridLogMessage << "predict dS    "<< dSpred <<std::endl;
  assert( fabs(real(Sprime-S-dSpred)) < 1.0 ) ;
  std::cout<< GridLogMessage << "Done" <<std::endl;
  Grid_finalize();
}