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118 lines
3.6 KiB
C++
118 lines
3.6 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 Grid {
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namespace QCD {
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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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RealD epsilon;
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WilsonGaugeAction &SG;
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void evolve_step();
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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):
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Nstep(Nstep),
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epsilon(epsilon),
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SG(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
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<< "[WilsonFlow] epsilon : " << epsilon
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<< "[WilsonFlow] full trajectory : " << Nstep * epsilon
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<< 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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RealD energyDensityPlaquette(unsigned int step, const GaugeField& U) const;
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};
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void WilsonFlow::evolve_step(GaugeField &U) {
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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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RealD 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(Uflow)/volume;
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}
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void WilsonFlow::smear(GaugeField& out, const GaugeField& in) const {
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out = in;
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RealD volume = out._grid->gSites();
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for (unsigned int step = 0; step < Nstep; step++) {
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evolve_step(out);
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// Energy density, plaquette
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std::cout << GridLogMessage
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<< "[WilsonFlow] Energy Density (step) : "
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<< step
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<< " " << energyDensityPlaquette(step, out)
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<< std::endl;
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}
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} // namespace QCD
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} // namespace Grid
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#endif // WILSONFLOW_H
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