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144 lines
3.7 KiB
C++
144 lines
3.7 KiB
C++
/*************************************************************************************
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Grid physics library, www.github.com/paboyle/Grid
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Source file: ./lib/qcd/hmc/integrators/Integrator.h
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Copyright (C) 2015
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Author: Guido Cossu <guido.cossu@ed.ac.uk>
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License along
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with this program; if not, write to the Free Software Foundation, Inc.,
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51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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See the full license in the file "LICENSE" in the top level distribution
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directory
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*************************************************************************************/
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/* END LEGAL */
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//--------------------------------------------------------------------
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#ifndef METRIC_H
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#define METRIC_H
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namespace Grid{
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namespace QCD{
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template <typename Field>
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class Metric{
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public:
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virtual void ImportGauge(const Field&) = 0;
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virtual void M(const Field&, Field&) = 0;
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virtual void Minv(const Field&, Field&) = 0;
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virtual void MSquareRoot(Field&) = 0;
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virtual void MDeriv(const Field&, Field&) = 0;
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};
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// Need a trivial operator
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template <typename Field>
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class TrivialMetric : public Metric<Field>{
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public:
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virtual void ImportGauge(const Field&){};
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virtual void M(const Field& in, Field& out){
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out = in;
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}
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virtual void Minv(const Field& in, Field& out){
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out = in;
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}
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virtual void MSquareRoot(Field& P){
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// do nothing
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}
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virtual void MDeriv(const Field& in, Field& out){
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out = zero;
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}
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};
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///////////////////////////////
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// Generalised momenta
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///////////////////////////////
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template <typename Implementation>
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class GeneralisedMomenta{
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public:
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typedef typename Implementation::Field MomentaField; //for readability
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typedef typename Implementation::GaugeLinkField MomentaLinkField; //for readability
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Metric<MomentaField>& M;
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MomentaField Mom;
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GeneralisedMomenta(GridBase* grid, Metric<MomentaField>& M): M(M), Mom(grid){}
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// Correct
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void MomentaDistribution(GridParallelRNG& pRNG){
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// Generate a distribution for
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// 1/2 P^dag G P
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// where G = M^-1
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// Generate gaussian momenta
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Implementation::generate_momenta(Mom, pRNG);
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// Modify the distribution with the metric
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M.MSquareRoot(Mom);
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}
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// Correct
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RealD MomentaAction(){
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MomentaField inv(Mom._grid);
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inv = zero;
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M.Minv(Mom, inv);
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LatticeComplex Hloc(Mom._grid);
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Hloc = zero;
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for (int mu = 0; mu < Nd; mu++) {
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// This is not very general
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// hide in the operators
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auto Mom_mu = PeekIndex<LorentzIndex>(Mom, mu);
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auto inv_mu = PeekIndex<LorentzIndex>(inv, mu);
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Hloc += trace(Mom_mu * inv_mu);
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}
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Complex Hsum = sum(Hloc);
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return Hsum.real();
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}
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// Correct
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void DerivativeU(MomentaField& in, MomentaField& der){
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// Compute the derivative of the kinetic term
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// with respect to the gauge field
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MomentaField MDer(in._grid);
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MomentaField X(in._grid);
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X = zero;
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M.Minv(in, X); // X = G in
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M.MDeriv(X, MDer); // MDer = U * dS/dU
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der = Implementation::projectForce(MDer); // Ta if gauge fields
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}
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//
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void DerivativeP(MomentaField& der){
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der = zero;
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M.Minv(Mom, der);
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der = Implementation::projectForce(der);
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}
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};
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}
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}
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#endif //METRIC_H
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