/* Monte-Carlo simulation code for statistical physics Copyright (C) 2001-2004 Sylvain Reynal Département de Physique Ecole Nationale Supérieure de l'Electronique et de ses Applications (ENSEA) 6, avenue du Ponceau, F-95014 CERGY CEDEX et Laboratoire de Physique Théorique et Modélisation (LPTM) Université de Cergy-Pontoise - Site de Neuville F-95031 CERGY CEDEX Tel : 00 +33 130 736 245 Fax : 00 +33 130 736 667 e-mail : reynal@ensea.fr web page : http://www.ensea.fr/staff/reynal/ */ package fr.ensea.montecarlo.multicanonical; import java.io.*; import java.awt.Color; import java.text.*; import fr.ensea.Localizer; import fr.ensea.montecarlo.model.*; import fr.ensea.montecarlo.data.*; import fr.ensea.montecarlo.canonical.*; import fr.ensea.montecarlo.misc.*; /** * Wang-Landau algorithm for the 2D antiferromagnetic Ising model */ public class AFIsingWL extends WangLandau { private AFIsingLattice lattice; /** * Init a new WL algorithm * @param weight initial weight for updating S(E), i.e. S(E)+=weight. * @param dE histogram bin width */ public AFIsingWL(AFIsingLattice lattice, SamplesBag bag, double dE, double weight) { super(bag, dE, weight); this.lattice = lattice; } /** * Attempts updating L*L spins. */ public void sweep(){ int row,col, neighborVal; double dE, oldSE, newSE; final int L = lattice.size; final int L2 = lattice.size2; for (int step=0; step < L2; step++){ attemptedMoves++; // pick at random a spin to be updated: row = (int)(L * createRandomNumber()); col = (int)(L * createRandomNumber()); oldSE = wlDosHistogram.getSE(lattice.getEnergy()); dE = lattice.getEnergyChange(row,col); // virtually toggle spin (row,col) newSE = wlDosHistogram.getSE(lattice.getEnergy()+dE); // attempt move: if (newSE <= oldSE || createRandomNumber() <= Math.exp(oldSE-newSE)){ acceptedMoves++; lattice.toggleSpin(row,col); lattice.energy += dE; } } samplesBag.addEnergySample(lattice.getEnergy()/lattice.size2); samplesBag.addMagnetizationSample(lattice.getMagnetization()); wlDosHistogram.fill(lattice.getEnergy()); } }