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Grid/lib/qcd/smearing/WilsonFlow.h

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/*************************************************************************************
Grid physics library, www.github.com/paboyle/Grid
Source file: ./lib/qcd/modules/plaquette.h
Copyright (C) 2017
Author: Guido Cossu <guido.cossu@ed.ac.uk>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
See the full license in the file "LICENSE" in the top level distribution
directory
*************************************************************************************/
/* END LEGAL */
#ifndef WILSONFLOW_H
#define WILSONFLOW_H
namespace Grid {
namespace QCD {
template <class Gimpl>
class WilsonFlow: public Smear<Gimpl>{
unsigned int Nstep;
unsigned int measure_interval;
mutable RealD epsilon, taus;
mutable WilsonGaugeAction<Gimpl> SG;
void evolve_step(typename Gimpl::GaugeField&) const;
void evolve_step_adaptive(typename Gimpl::GaugeField&, RealD);
RealD tau(unsigned int t)const {return epsilon*(t+1.0); }
public:
INHERIT_GIMPL_TYPES(Gimpl)
explicit WilsonFlow(unsigned int Nstep, RealD epsilon, unsigned int interval = 1):
Nstep(Nstep),
epsilon(epsilon),
measure_interval(interval),
SG(WilsonGaugeAction<Gimpl>(3.0)) {
// WilsonGaugeAction with beta 3.0
assert(epsilon > 0.0);
LogMessage();
}
void LogMessage() {
std::cout << GridLogMessage
<< "[WilsonFlow] Nstep : " << Nstep << std::endl;
std::cout << GridLogMessage
<< "[WilsonFlow] epsilon : " << epsilon << std::endl;
std::cout << GridLogMessage
<< "[WilsonFlow] full trajectory : " << Nstep * epsilon << std::endl;
}
virtual void smear(GaugeField&, const GaugeField&) const;
virtual void derivative(GaugeField&, const GaugeField&, const GaugeField&) const {
assert(0);
// undefined for WilsonFlow
}
void smear_adaptive(GaugeField&, const GaugeField&, RealD maxTau);
RealD energyDensityPlaquette(unsigned int step, const GaugeField& U) const;
RealD energyDensityPlaquette(const GaugeField& U) const;
};
////////////////////////////////////////////////////////////////////////////////
// Implementations
////////////////////////////////////////////////////////////////////////////////
template <class Gimpl>
void WilsonFlow<Gimpl>::evolve_step(typename Gimpl::GaugeField &U) const{
GaugeField Z(U._grid);
GaugeField tmp(U._grid);
SG.deriv(U, Z);
Z *= 0.25; // Z0 = 1/4 * F(U)
Gimpl::update_field(Z, U, -2.0*epsilon); // U = W1 = exp(ep*Z0)*W0
Z *= -17.0/8.0;
SG.deriv(U, tmp); Z += tmp; // -17/32*Z0 +Z1
Z *= 8.0/9.0; // Z = -17/36*Z0 +8/9*Z1
Gimpl::update_field(Z, U, -2.0*epsilon); // U_= W2 = exp(ep*Z)*W1
Z *= -4.0/3.0;
SG.deriv(U, tmp); Z += tmp; // 4/3*(17/36*Z0 -8/9*Z1) +Z2
Z *= 3.0/4.0; // Z = 17/36*Z0 -8/9*Z1 +3/4*Z2
Gimpl::update_field(Z, U, -2.0*epsilon); // V(t+e) = exp(ep*Z)*W2
}
template <class Gimpl>
void WilsonFlow<Gimpl>::evolve_step_adaptive(typename Gimpl::GaugeField &U, RealD maxTau) {
if (maxTau - taus < epsilon){
epsilon = maxTau-taus;
}
//std::cout << GridLogMessage << "Integration epsilon : " << epsilon << std::endl;
GaugeField Z(U._grid);
GaugeField Zprime(U._grid);
GaugeField tmp(U._grid), Uprime(U._grid);
Uprime = U;
SG.deriv(U, Z);
Zprime = -Z;
Z *= 0.25; // Z0 = 1/4 * F(U)
Gimpl::update_field(Z, U, -2.0*epsilon); // U = W1 = exp(ep*Z0)*W0
Z *= -17.0/8.0;
SG.deriv(U, tmp); Z += tmp; // -17/32*Z0 +Z1
Zprime += 2.0*tmp;
Z *= 8.0/9.0; // Z = -17/36*Z0 +8/9*Z1
Gimpl::update_field(Z, U, -2.0*epsilon); // U_= W2 = exp(ep*Z)*W1
Z *= -4.0/3.0;
SG.deriv(U, tmp); Z += tmp; // 4/3*(17/36*Z0 -8/9*Z1) +Z2
Z *= 3.0/4.0; // Z = 17/36*Z0 -8/9*Z1 +3/4*Z2
Gimpl::update_field(Z, U, -2.0*epsilon); // V(t+e) = exp(ep*Z)*W2
// Ramos
Gimpl::update_field(Zprime, Uprime, -2.0*epsilon); // V'(t+e) = exp(ep*Z')*W0
// Compute distance as norm^2 of the difference
GaugeField diffU = U - Uprime;
RealD diff = norm2(diffU);
// adjust integration step
taus += epsilon;
//std::cout << GridLogMessage << "Adjusting integration step with distance: " << diff << std::endl;
epsilon = epsilon*0.95*std::pow(1e-4/diff,1./3.);
//std::cout << GridLogMessage << "New epsilon : " << epsilon << std::endl;
}
template <class Gimpl>
RealD WilsonFlow<Gimpl>::energyDensityPlaquette(unsigned int step, const GaugeField& U) const {
RealD td = tau(step);
return 2.0 * td * td * SG.S(U)/U._grid->gSites();
}
template <class Gimpl>
RealD WilsonFlow<Gimpl>::energyDensityPlaquette(const GaugeField& U) const {
return 2.0 * taus * taus * SG.S(U)/U._grid->gSites();
}
//#define WF_TIMING
template <class Gimpl>
void WilsonFlow<Gimpl>::smear(GaugeField& out, const GaugeField& in) const {
out = in;
for (unsigned int step = 1; step <= Nstep; step++) {
auto start = std::chrono::high_resolution_clock::now();
evolve_step(out);
auto end = std::chrono::high_resolution_clock::now();
std::chrono::duration<double> diff = end - start;
#ifdef WF_TIMING
std::cout << "Time to evolve " << diff.count() << " s\n";
#endif
std::cout << GridLogMessage << "[WilsonFlow] Energy density (plaq) : "
<< step << " " << tau(step) << " "
<< energyDensityPlaquette(step,out) << std::endl;
if( step % measure_interval == 0){
std::cout << GridLogMessage << "[WilsonFlow] Top. charge : "
<< step << " "
<< WilsonLoops<PeriodicGimplR>::TopologicalCharge(out) << std::endl;
}
}
}
template <class Gimpl>
void WilsonFlow<Gimpl>::smear_adaptive(GaugeField& out, const GaugeField& in, RealD maxTau){
out = in;
taus = epsilon;
unsigned int step = 0;
do{
step++;
//std::cout << GridLogMessage << "Evolution time :"<< taus << std::endl;
evolve_step_adaptive(out, maxTau);
std::cout << GridLogMessage << "[WilsonFlow] Energy density (plaq) : "
<< step << " " << taus << " "
<< energyDensityPlaquette(out) << std::endl;
if( step % measure_interval == 0){
std::cout << GridLogMessage << "[WilsonFlow] Top. charge : "
<< step << " "
<< WilsonLoops<PeriodicGimplR>::TopologicalCharge(out) << std::endl;
}
} while (taus < maxTau);
}
} // namespace QCD
} // namespace Grid
#endif // WILSONFLOW_H
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