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128 lines
3.4 KiB
C++
128 lines
3.4 KiB
C++
#include <Grid/Grid.h>
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using namespace Grid;
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// Function used for Chebyshev smearing
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//
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Real MomentumSmearing(Real p2)
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{
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return (1 - 4.0*p2) * exp(-p2/4);
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}
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Real DistillationSmearing(Real p2)
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{
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if ( p2 > 0.5 ) return 0.0;
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else return 1.0;
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}
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// Flip sign to make prop to p^2, not -p^2 relative to last example
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template<class Gimpl,class Field> class CovariantLaplacianCshift : public SparseMatrixBase<Field>
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{
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public:
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INHERIT_GIMPL_TYPES(Gimpl);
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GridBase *grid;
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GaugeField U;
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CovariantLaplacianCshift(GaugeField &_U) :
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grid(_U.Grid()),
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U(_U) { };
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virtual GridBase *Grid(void) { return grid; };
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virtual void M (const Field &in, Field &out)
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{
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out=Zero();
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for(int mu=0;mu<Nd-1;mu++) {
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GaugeLinkField Umu = PeekIndex<LorentzIndex>(U, mu); // NB: Inefficent
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out = out - Gimpl::CovShiftForward(Umu,mu,in);
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out = out - Gimpl::CovShiftBackward(Umu,mu,in);
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out = out + 2.0*in;
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}
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};
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virtual void Mdag (const Field &in, Field &out) { M(in,out);}; // Laplacian is hermitian
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virtual void Mdiag (const Field &in, Field &out) {assert(0);}; // Unimplemented need only for multigrid
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virtual void Mdir (const Field &in, Field &out,int dir, int disp){assert(0);}; // Unimplemented need only for multigrid
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virtual void MdirAll (const Field &in, std::vector<Field> &out) {assert(0);}; // Unimplemented need only for multigrid
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};
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int main(int argc, char ** argv)
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{
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Grid_init(&argc, &argv);
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typedef LatticeColourVector Field;
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auto latt_size = GridDefaultLatt();
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auto simd_layout = GridDefaultSimd(Nd,vComplex::Nsimd());
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auto mpi_layout = GridDefaultMpi();
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GridCartesian Grid(latt_size,simd_layout,mpi_layout);
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GridParallelRNG RNG(&Grid); RNG.SeedFixedIntegers(std::vector<int>({45,12,81,9}));
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LatticeGaugeField U(&Grid);
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SU<Nc>::ColdConfiguration(RNG,U);
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typedef CovariantLaplacianCshift <PeriodicGimplR,Field> Laplacian_t;
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Laplacian_t Laplacian(U);
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ColourVector ColourKronecker;
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ColourKronecker = Zero();
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ColourKronecker()()(0) = 1.0;
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Coordinate site({latt_size[0]/2,
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latt_size[1]/2,
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latt_size[2]/2,
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0});
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Field kronecker(&Grid);
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kronecker = Zero();
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pokeSite(ColourKronecker,kronecker,site);
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Field psi(&Grid), chi(&Grid);
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//////////////////////////////////////
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// Classic Wuppertal smearing
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//////////////////////////////////////
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Integer Iterations = 80;
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Real width = 2.0;
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Real coeff = (width*width) / Real(4*Iterations);
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chi=kronecker;
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// chi = (1-p^2/2N)^N kronecker
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for(int n = 0; n < Iterations; ++n) {
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Laplacian.M(chi,psi);
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chi = chi - coeff*psi;
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}
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std::cout << " Wuppertal smeared operator is chi = \n" << chi <<std::endl;
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/////////////////////////////////////
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// Chebyshev smearing
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/////////////////////////////////////
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RealD lo = 0.0;
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RealD hi = 12.0; // Analytic free field bound
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HermitianLinearOperator<Laplacian_t,Field> HermOp(Laplacian);
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std::cout << " Checking spectral range of our POSITIVE definite operator \n";
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PowerMethod<Field> PM;
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PM(HermOp,kronecker);
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Chebyshev<Field> ChebySmear(lo,hi,20,DistillationSmearing);
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// Chebyshev<Field> ChebySmear(lo,hi,20,MomentumSmearing);
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{
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std::ofstream of("chebysmear");
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ChebySmear.csv(of);
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}
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ChebySmear(HermOp,kronecker,chi);
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std::cout << " Chebyshev smeared operator is chi = \n" << chi <<std::endl;
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Grid_finalize();
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}
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