Grid/tests/Test_dwf_force.cc

#include <Grid.h>

using namespace std;
using namespace Grid;
using namespace Grid::QCD;

#define parallel_for PARALLEL_FOR_LOOP for

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

  std::vector<int> latt_size   = GridDefaultLatt();
  std::vector<int> simd_layout = GridDefaultSimd(Nd,vComplex::Nsimd());
  std::vector<int> 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;

  LatticeFermion phi        (FGrid); gaussian(RNG5,phi);
  LatticeFermion Mphi       (FGrid); 
  LatticeFermion MphiPrime  (FGrid); 

  LatticeGaugeField U(UGrid);

  SU3::HotConfiguration(RNG4,U);
  
  ////////////////////////////////////
  // Unmodified matrix element
  ////////////////////////////////////
  RealD mass=0.01; 
  RealD M5=1.8; 
  DomainWallFermionR Ddwf(U,*FGrid,*FrbGrid,*UGrid,*UrbGrid,mass,M5);
  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);  
  
  LatticeFermion 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::GaussianLieAlgebraMatrix(RNG4, mommu); // Traceless antihermitian momentum; gaussian in lie alg

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

    // fourth order exponential approx
    parallel_for(auto i=mom.begin();i<mom.end();i++){
      Uprime[i](mu) =
	  U[i](mu)
	+ mom[i](mu)*U[i](mu)*dt 
	+ mom[i](mu) *mom[i](mu) *U[i](mu)*(dt*dt/2.0)
	+ mom[i](mu) *mom[i](mu) *mom[i](mu) *U[i](mu)*(dt*dt*dt/6.0)
	+ mom[i](mu) *mom[i](mu) *mom[i](mu) *mom[i](mu) *U[i](mu)*(dt*dt*dt*dt/24.0)
	+ mom[i](mu) *mom[i](mu) *mom[i](mu) *mom[i](mu) *mom[i](mu) *U[i](mu)*(dt*dt*dt*dt*dt/120.0)
	+ mom[i](mu) *mom[i](mu) *mom[i](mu) *mom[i](mu) *mom[i](mu) *mom[i](mu) *U[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;

  }

  Complex dSpred    = sum(dS);

  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;

  std::cout<< GridLogMessage << "Done" <<std::endl;
  Grid_finalize();
}