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212 lines
6.9 KiB
C++
212 lines
6.9 KiB
C++
/*************************************************************************************
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Grid physics library, www.github.com/paboyle/Grid
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Source file: ./lib/qcd/modules/plaquette.h
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Copyright (C) 2017
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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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#ifndef WILSONFLOW_H
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#define WILSONFLOW_H
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NAMESPACE_BEGIN(Grid);
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template <class Gimpl>
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class WilsonFlow: public Smear<Gimpl>{
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unsigned int Nstep;
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unsigned int measure_interval;
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mutable RealD epsilon, taus;
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mutable WilsonGaugeAction<Gimpl> SG;
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void evolve_step(typename Gimpl::GaugeField&) const;
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void evolve_step_adaptive(typename Gimpl::GaugeField&, RealD);
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RealD tau(unsigned int t)const {return epsilon*(t+1.0); }
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public:
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INHERIT_GIMPL_TYPES(Gimpl)
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explicit WilsonFlow(unsigned int Nstep, RealD epsilon, unsigned int interval = 1):
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Nstep(Nstep),
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epsilon(epsilon),
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measure_interval(interval),
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SG(WilsonGaugeAction<Gimpl>(3.0)) {
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// WilsonGaugeAction with beta 3.0
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assert(epsilon > 0.0);
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LogMessage();
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}
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void LogMessage() {
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std::cout << GridLogMessage
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<< "[WilsonFlow] Nstep : " << Nstep << std::endl;
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std::cout << GridLogMessage
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<< "[WilsonFlow] epsilon : " << epsilon << std::endl;
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std::cout << GridLogMessage
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<< "[WilsonFlow] full trajectory : " << Nstep * epsilon << std::endl;
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}
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virtual void smear(GaugeField&, const GaugeField&) const;
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virtual void derivative(GaugeField&, const GaugeField&, const GaugeField&) const {
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assert(0);
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// undefined for WilsonFlow
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}
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void smear_adaptive(GaugeField&, const GaugeField&, RealD maxTau);
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RealD energyDensityPlaquette(unsigned int step, const GaugeField& U) const;
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RealD energyDensityPlaquette(const GaugeField& U) const;
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};
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////////////////////////////////////////////////////////////////////////////////
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// Implementations
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////////////////////////////////////////////////////////////////////////////////
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template <class Gimpl>
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void WilsonFlow<Gimpl>::evolve_step(typename Gimpl::GaugeField &U) const{
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GaugeField Z(U.Grid());
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GaugeField tmp(U.Grid());
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SG.deriv(U, Z);
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Z *= 0.25; // Z0 = 1/4 * F(U)
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Gimpl::update_field(Z, U, -2.0*epsilon); // U = W1 = exp(ep*Z0)*W0
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Z *= -17.0/8.0;
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SG.deriv(U, tmp); Z += tmp; // -17/32*Z0 +Z1
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Z *= 8.0/9.0; // Z = -17/36*Z0 +8/9*Z1
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Gimpl::update_field(Z, U, -2.0*epsilon); // U_= W2 = exp(ep*Z)*W1
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Z *= -4.0/3.0;
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SG.deriv(U, tmp); Z += tmp; // 4/3*(17/36*Z0 -8/9*Z1) +Z2
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Z *= 3.0/4.0; // Z = 17/36*Z0 -8/9*Z1 +3/4*Z2
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Gimpl::update_field(Z, U, -2.0*epsilon); // V(t+e) = exp(ep*Z)*W2
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}
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template <class Gimpl>
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void WilsonFlow<Gimpl>::evolve_step_adaptive(typename Gimpl::GaugeField &U, RealD maxTau) {
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if (maxTau - taus < epsilon){
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epsilon = maxTau-taus;
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}
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//std::cout << GridLogMessage << "Integration epsilon : " << epsilon << std::endl;
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GaugeField Z(U.Grid());
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GaugeField Zprime(U.Grid());
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GaugeField tmp(U.Grid()), Uprime(U.Grid());
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Uprime = U;
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SG.deriv(U, Z);
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Zprime = -Z;
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Z *= 0.25; // Z0 = 1/4 * F(U)
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Gimpl::update_field(Z, U, -2.0*epsilon); // U = W1 = exp(ep*Z0)*W0
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Z *= -17.0/8.0;
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SG.deriv(U, tmp); Z += tmp; // -17/32*Z0 +Z1
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Zprime += 2.0*tmp;
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Z *= 8.0/9.0; // Z = -17/36*Z0 +8/9*Z1
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Gimpl::update_field(Z, U, -2.0*epsilon); // U_= W2 = exp(ep*Z)*W1
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Z *= -4.0/3.0;
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SG.deriv(U, tmp); Z += tmp; // 4/3*(17/36*Z0 -8/9*Z1) +Z2
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Z *= 3.0/4.0; // Z = 17/36*Z0 -8/9*Z1 +3/4*Z2
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Gimpl::update_field(Z, U, -2.0*epsilon); // V(t+e) = exp(ep*Z)*W2
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// Ramos
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Gimpl::update_field(Zprime, Uprime, -2.0*epsilon); // V'(t+e) = exp(ep*Z')*W0
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// Compute distance as norm^2 of the difference
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GaugeField diffU = U - Uprime;
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RealD diff = norm2(diffU);
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// adjust integration step
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taus += epsilon;
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//std::cout << GridLogMessage << "Adjusting integration step with distance: " << diff << std::endl;
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epsilon = epsilon*0.95*std::pow(1e-4/diff,1./3.);
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//std::cout << GridLogMessage << "New epsilon : " << epsilon << std::endl;
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}
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template <class Gimpl>
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RealD WilsonFlow<Gimpl>::energyDensityPlaquette(unsigned int step, const GaugeField& U) const {
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RealD td = tau(step);
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return 2.0 * td * td * SG.S(U)/U.Grid()->gSites();
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}
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template <class Gimpl>
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RealD WilsonFlow<Gimpl>::energyDensityPlaquette(const GaugeField& U) const {
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return 2.0 * taus * taus * SG.S(U)/U.Grid()->gSites();
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}
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//#define WF_TIMING
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template <class Gimpl>
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void WilsonFlow<Gimpl>::smear(GaugeField& out, const GaugeField& in) const {
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out = in;
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for (unsigned int step = 1; step <= Nstep; step++) {
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auto start = std::chrono::high_resolution_clock::now();
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evolve_step(out);
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auto end = std::chrono::high_resolution_clock::now();
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std::chrono::duration<double> diff = end - start;
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#ifdef WF_TIMING
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std::cout << "Time to evolve " << diff.count() << " s\n";
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#endif
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std::cout << GridLogMessage << "[WilsonFlow] Energy density (plaq) : "
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<< step << " "
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<< energyDensityPlaquette(step,out) << std::endl;
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if( step % measure_interval == 0){
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std::cout << GridLogMessage << "[WilsonFlow] Top. charge : "
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<< step << " "
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<< WilsonLoops<PeriodicGimplR>::TopologicalCharge(out) << std::endl;
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}
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}
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}
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template <class Gimpl>
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void WilsonFlow<Gimpl>::smear_adaptive(GaugeField& out, const GaugeField& in, RealD maxTau){
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out = in;
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taus = epsilon;
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unsigned int step = 0;
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do{
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step++;
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//std::cout << GridLogMessage << "Evolution time :"<< taus << std::endl;
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evolve_step_adaptive(out, maxTau);
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std::cout << GridLogMessage << "[WilsonFlow] Energy density (plaq) : "
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<< step << " "
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<< energyDensityPlaquette(out) << std::endl;
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if( step % measure_interval == 0){
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std::cout << GridLogMessage << "[WilsonFlow] Top. charge : "
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<< step << " "
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<< WilsonLoops<PeriodicGimplR>::TopologicalCharge(out) << std::endl;
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}
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} while (taus < maxTau);
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}
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NAMESPACE_END(Grid);
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#endif // WILSONFLOW_H
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