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Peter Boyle 2021-08-22 18:28:39 +01:00
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commit ec9c3fe77a
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examples/Example_Laplacian_inverter.cc
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#include <Grid/Grid.h>
using namespace Grid;
// Function used for Chebyshev smearing
//
Real MomentumSmearing(Real p2)
{
return (1 - 4.0*p2) * exp(-p2/4);
}
Real DistillationSmearing(Real p2)
{
if ( p2 > 0.5 ) return 0.0;
else return 1.0;
}
// Flip sign to make prop to p^2, not -p^2 relative to last example
template<class Gimpl,class Field> class CovariantLaplacianCshift : public SparseMatrixBase<Field>
{
public:
INHERIT_GIMPL_TYPES(Gimpl);
GridBase *grid;
GaugeField U;
CovariantLaplacianCshift(GaugeField &_U) :
grid(_U.Grid()),
U(_U) { };
virtual GridBase *Grid(void) { return grid; };
virtual void M (const Field &in, Field &out)
{
out=Zero();
for(int mu=0;mu<Nd-1;mu++) {
GaugeLinkField Umu = PeekIndex<LorentzIndex>(U, mu); // NB: Inefficent
out = out - Gimpl::CovShiftForward(Umu,mu,in);
out = out - Gimpl::CovShiftBackward(Umu,mu,in);
out = out + 2.0*in;
}
};
virtual void Mdag (const Field &in, Field &out) { M(in,out);}; // Laplacian is hermitian
virtual void Mdiag (const Field &in, Field &out) {assert(0);}; // Unimplemented need only for multigrid
virtual void Mdir (const Field &in, Field &out,int dir, int disp){assert(0);}; // Unimplemented need only for multigrid
virtual void MdirAll (const Field &in, std::vector<Field> &out) {assert(0);}; // Unimplemented need only for multigrid
};
int main(int argc, char ** argv)
{
Grid_init(&argc, &argv);
typedef LatticeColourVector Field;
auto latt_size = GridDefaultLatt();
auto simd_layout = GridDefaultSimd(Nd,vComplex::Nsimd());
auto mpi_layout = GridDefaultMpi();
GridCartesian Grid(latt_size,simd_layout,mpi_layout);
GridParallelRNG RNG(&Grid); RNG.SeedFixedIntegers(std::vector<int>({45,12,81,9}));
LatticeGaugeField U(&Grid);
SU<Nc>::ColdConfiguration(RNG,U);
typedef CovariantLaplacianCshift <PeriodicGimplR,Field> Laplacian_t;
Laplacian_t Laplacian(U);
ColourVector ColourKronecker;
ColourKronecker = Zero();
ColourKronecker()()(0) = 1.0;
Coordinate site({latt_size[0]/2,
latt_size[1]/2,
latt_size[2]/2,
0});
Field kronecker(&Grid);
kronecker = Zero();
pokeSite(ColourKronecker,kronecker,site);
Field psi(&Grid), chi(&Grid);
//////////////////////////////////////
// Classic Wuppertal smearing
//////////////////////////////////////
Integer Iterations = 80;
Real width = 2.0;
Real coeff = (width*width) / Real(4*Iterations);
chi=kronecker;
// chi = (1-p^2/2N)^N kronecker
for(int n = 0; n < Iterations; ++n) {
Laplacian.M(chi,psi);
chi = chi - coeff*psi;
}
std::cout << " Wuppertal smeared operator is chi = \n" << chi <<std::endl;
/////////////////////////////////////
// Chebyshev smearing
/////////////////////////////////////
RealD lo = 0.0;
RealD hi = 128;
HermitianLinearOperator<Laplacian_t,Field> HermOp(Laplacian);
Chebyshev<Field> ChebySmear(lo,hi,20,DistillationSmearing);
// Chebyshev<Field> ChebySmear(lo,hi,20,MomentumSmearing);
{
std::ofstream of("chebysmear");
ChebySmear.csv(of);
}
ChebySmear(HermOp,kronecker,chi);
std::cout << " Chebyshev smeared operator is chi = \n" << chi <<std::endl;
Grid_finalize();
}