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Grid/examples/Example_Laplacian.cc
2021-08-23 23:14:26 +01:00

397 lines
14 KiB
C++

#include <Grid/Grid.h>
using namespace Grid;
/*
/////////////////////////////////////////////////////////////////////////////////////////////
// Grid/algorithms/SparseMatrix.h: Interface defining what I expect of a general sparse matrix, such as a Fermion action
/////////////////////////////////////////////////////////////////////////////////////////////
template<class Field> class SparseMatrixBase {
public:
virtual GridBase *Grid(void) =0;
virtual void M (const Field &in, Field &out)=0;
virtual void Mdag (const Field &in, Field &out)=0;
virtual void MdagM(const Field &in, Field &out) {
Field tmp (in.Grid());
M(in,tmp);
Mdag(tmp,out);
}
virtual void Mdiag (const Field &in, Field &out)=0;
virtual void Mdir (const Field &in, Field &out,int dir, int disp)=0;
virtual void MdirAll (const Field &in, std::vector<Field> &out)=0;
};
*/
const std::vector<int> directions ({Xdir,Ydir,Zdir,Xdir,Ydir,Zdir});
const std::vector<int> displacements({1,1,1,-1,-1,-1});
template<class Field> class FreeLaplacianCshift : public SparseMatrixBase<Field>
{
public:
GridBase *grid;
FreeLaplacianCshift(GridBase *_grid)
{
grid=_grid;
};
virtual GridBase *Grid(void) { return grid; };
virtual void M (const Field &in, Field &out)
{
out = Zero();
for(int mu=0;mu<Nd-1;mu++) {
out = out + Cshift(in,mu,1) + Cshift(in,mu,-1) - 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
};
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
};
#define LEG_LOAD(Dir) \
SE = st.GetEntry(ptype, Dir, ss); \
if (SE->_is_local ) { \
int perm= SE->_permute; \
chi = coalescedReadPermute(in[SE->_offset],ptype,perm,lane); \
} else { \
chi = coalescedRead(buf[SE->_offset],lane); \
} \
acceleratorSynchronise();
template<class Field> class FreeLaplacianStencil : public SparseMatrixBase<Field>
{
public:
typedef typename Field::vector_object siteObject;
typedef CartesianStencil<siteObject, siteObject, int> StencilImpl;
GridBase *grid;
StencilImpl Stencil;
SimpleCompressor<siteObject> Compressor;
FreeLaplacianStencil(GridBase *_grid)
: Stencil (_grid,6,Even,directions,displacements,0), grid(_grid)
{ };
virtual GridBase *Grid(void) { return grid; };
virtual void M (const Field &_in, Field &_out)
{
///////////////////////////////////////////////
// Halo exchange for this geometry of stencil
///////////////////////////////////////////////
Stencil.HaloExchange(_in, Compressor);
///////////////////////////////////
// Arithmetic expressions
///////////////////////////////////
// Views; device friendly/accessible pointers
auto st = Stencil.View(AcceleratorRead);
auto buf = st.CommBuf();
autoView( in , _in , AcceleratorRead);
autoView( out , _out , AcceleratorWrite);
typedef typename Field::vector_object vobj;
typedef decltype(coalescedRead(in[0])) calcObj;
const int Nsimd = vobj::Nsimd();
const uint64_t NN = grid->oSites();
accelerator_for( ss, NN, Nsimd, {
StencilEntry *SE;
const int lane=acceleratorSIMTlane(Nsimd);
calcObj chi;
calcObj res;
int ptype;
res = coalescedRead(in[ss])*(-6.0);
LEG_LOAD(0); res = res + chi;
LEG_LOAD(1); res = res + chi;
LEG_LOAD(2); res = res + chi;
LEG_LOAD(3); res = res + chi;
LEG_LOAD(4); res = res + chi;
LEG_LOAD(5); res = res + chi;
coalescedWrite(out[ss], res,lane);
});
};
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
};
template<class Gimpl,class Field> class CovariantLaplacianStencil : public SparseMatrixBase<Field>
{
public:
INHERIT_GIMPL_TYPES(Gimpl);
typedef typename Field::vector_object siteObject;
template <typename vtype> using iImplDoubledGaugeField = iVector<iScalar<iMatrix<vtype, Nc> >, Nds>;
typedef iImplDoubledGaugeField<Simd> SiteDoubledGaugeField;
typedef Lattice<SiteDoubledGaugeField> DoubledGaugeField;
typedef CartesianStencil<siteObject, siteObject, int> StencilImpl;
GridBase *grid;
StencilImpl Stencil;
SimpleCompressor<siteObject> Compressor;
DoubledGaugeField Uds;
CovariantLaplacianStencil(GaugeField &Umu)
:
grid(Umu.Grid()),
Stencil (grid,6,Even,directions,displacements,0),
Uds(grid)
{
for (int mu = 0; mu < Nd; mu++) {
auto U = PeekIndex<LorentzIndex>(Umu, mu);
PokeIndex<LorentzIndex>(Uds, U, mu );
U = adj(Cshift(U, mu, -1));
PokeIndex<LorentzIndex>(Uds, U, mu + 4);
}
};
virtual GridBase *Grid(void) { return grid; };
virtual void M (const Field &_in, Field &_out)
{
///////////////////////////////////////////////
// Halo exchange for this geometry of stencil
///////////////////////////////////////////////
Stencil.HaloExchange(_in, Compressor);
///////////////////////////////////
// Arithmetic expressions
///////////////////////////////////
auto st = Stencil.View(AcceleratorRead);
auto buf = st.CommBuf();
autoView( in , _in , AcceleratorRead);
autoView( out , _out , AcceleratorWrite);
autoView( U , Uds , AcceleratorRead);
typedef typename Field::vector_object vobj;
typedef decltype(coalescedRead(in[0])) calcObj;
typedef decltype(coalescedRead(U[0](0))) calcLink;
const int Nsimd = vobj::Nsimd();
const uint64_t NN = grid->oSites();
accelerator_for( ss, NN, Nsimd, {
StencilEntry *SE;
const int lane=acceleratorSIMTlane(Nsimd);
calcObj chi;
calcObj res;
calcObj Uchi;
calcLink UU;
int ptype;
res = coalescedRead(in[ss])*(-6.0);
#define LEG_LOAD_MULT(leg,polarisation) \
UU = coalescedRead(U[ss](polarisation)); \
LEG_LOAD(leg); \
mult(&Uchi(), &UU, &chi()); \
res = res + Uchi;
LEG_LOAD_MULT(0,Xp);
LEG_LOAD_MULT(1,Yp);
LEG_LOAD_MULT(2,Zp);
LEG_LOAD_MULT(3,Xm);
LEG_LOAD_MULT(4,Ym);
LEG_LOAD_MULT(5,Zm);
coalescedWrite(out[ss], res,lane);
});
};
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
};
#undef LEG_LOAD_MULT
#undef LEG_LOAD
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}));
FreeLaplacianCshift<Field> FLcs(&Grid);
FreeLaplacianStencil<Field> FLst(&Grid);
LatticeGaugeField U(&Grid);
SU<Nc>::ColdConfiguration(RNG,U);
std::cout << " Gauge field has norm " <<norm2(U)<<std::endl;
CovariantLaplacianCshift <PeriodicGimplR,Field> CLcs(U);
CovariantLaplacianStencil<PeriodicGimplR,Field> CLst(U);
Field in(&Grid); gaussian(RNG,in);
Field out_FLcs(&Grid);
Field out_FLst(&Grid);
Field out_CLcs(&Grid);
Field out_CLst(&Grid);
Field diff(&Grid);
////////////////////////////////////////////////////////
// First test: in free field these should all agree
////////////////////////////////////////////////////////
FLcs.M(in,out_FLcs);
FLst.M(in,out_FLst);
CLcs.M(in,out_CLcs);
CLst.M(in,out_CLst);
std:: cout << "******************************************************************" <<std::endl;
std:: cout << " Test A: consistency of four different Laplacian implementations " <<std::endl;
std:: cout << "******************************************************************" <<std::endl;
std:: cout << " Input test vector " <<norm2(in)<<std::endl;
std:: cout << "--------------------------------------------------------" <<std::endl;
std:: cout << " Free cshift output vector " <<norm2(out_FLcs)<<std::endl;
std:: cout << " Free stencil output vector " <<norm2(out_FLst)<<std::endl;
std:: cout << " Cov cshift output vector " <<norm2(out_CLcs)<<std::endl;
std:: cout << " Cov stencil output vector " <<norm2(out_CLst)<<std::endl;
std:: cout << "--------------------------------------------------------" <<std::endl;
diff = out_FLcs - out_FLst;
std:: cout << " Difference between free Cshift Laplacian and free Stencil Laplacian = " <<norm2(diff)<<std::endl;
diff = out_FLcs - out_CLcs;
std:: cout << " Difference between free Cshift Laplacian and covariant Cshift Laplacian = " <<norm2(diff)<<std::endl;
diff = out_FLcs - out_CLst;
std:: cout << " Difference between free Cshift Laplacian and covariant Stencil Laplacian = " <<norm2(diff)<<std::endl;
std:: cout << "--------------------------------------------------------" <<std::endl;
std:: cout << "******************************************************************" <<std::endl;
std:: cout << " Test B: gauge covariance " <<std::endl;
std:: cout << "******************************************************************" <<std::endl;
LatticeGaugeField U_GT(&Grid); // Gauge transformed field
LatticeColourMatrix g(&Grid); // local Gauge xform matrix
U_GT = U;
// Make a random xform to teh gauge field
SU<Nc>::RandomGaugeTransform(RNG,U_GT,g); // Unit gauge
Field in_GT(&Grid);
Field out_GT(&Grid);
Field out_CLcs_GT(&Grid);
Field out_CLst_GT(&Grid);
CovariantLaplacianCshift <PeriodicGimplR,Field> CLcs_GT(U_GT);
CovariantLaplacianStencil<PeriodicGimplR,Field> CLst_GT(U_GT);
in_GT = g*in;
out_GT = g*out_FLcs;
// Check M^GT_xy in_GT = g(x) M_xy g^dag(y) g(y) in = g(x) out(x)
CLcs_GT.M(in_GT,out_CLcs_GT);
CLst_GT.M(in_GT,out_CLst_GT);
diff = out_CLcs_GT - out_GT;
std:: cout << " Difference between Gauge xformed result and covariant Cshift Laplacian in xformed gauge = " <<norm2(diff)<<std::endl;
diff = out_CLst_GT - out_GT;
std:: cout << " Difference between Gauge xformed result and covariant Stencil Laplacian in xformed gauge = " <<norm2(diff)<<std::endl;
std:: cout << "--------------------------------------------------------" <<std::endl;
std:: cout << "******************************************************************" <<std::endl;
std:: cout << " Test C: compare in free Field to \"Feynman rule\" " <<std::endl;
std:: cout << "******************************************************************" <<std::endl;
std::vector<int> dim_mask({1,1,1,0}); // 3d FFT
FFT theFFT(&Grid);
Field out(&Grid);
Field F_out(&Grid);
Field F_in(&Grid);
// FFT the random input vector
theFFT.FFT_dim_mask(F_in,in,dim_mask,FFT::forward);
// Convolution theorem: multiply by Fourier representation of (discrete) Laplacian to apply diff op
LatticeComplexD lap(&Grid); lap = Zero();
LatticeComplexD kmu(&Grid);
ComplexD ci(0.0,1.0);
for(int mu=0;mu<3;mu++) {
RealD TwoPiL = M_PI * 2.0/ latt_size[mu];
LatticeCoordinate(kmu,mu);
kmu = TwoPiL * kmu;
// (e^ik_mu + e^-ik_mu - 2) = 2( cos kmu - 1) ~ 2 (1 - k_mu^2/2 -1 ) = - k_mu^2 + O(k^4)
lap = lap + 2.0*cos(kmu) - 2.0;
}
F_out = lap * F_in;
// Inverse FFT the result
theFFT.FFT_dim_mask(out,F_out,dim_mask,FFT::backward);
std::cout<<"Fourier xformed (in) "<<norm2(F_in)<<std::endl;
std::cout<<"Fourier xformed Laplacian x (in) "<<norm2(F_out)<<std::endl;
std::cout<<"Momentum space Laplacian application "<< norm2(out)<<std::endl;
std::cout<<"Stencil Laplacian application "<< norm2(out_CLcs)<<std::endl;
diff = out_CLcs - out;
std::cout<<"diff "<< norm2(diff)<<std::endl;
Grid_finalize();
}