Java tutorial
/** * Copyright (C) 2012, Emergya (http://www.emergya.es) * * @author <a href="mailto:marias@emergya.com">Mara Arias de Reyna</a> * * This file is part of GoFleet * * This software 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 software 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 library; if not, write to the Free Software * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA * 02110-1301 USA * * As a special exception, if you link this library with other files to * produce an executable, this library does not by itself cause the * resulting executable to be covered by the GNU General Public License. * This exception does not however invalidate any other reasons why the * executable file might be covered by the GNU General Public License. */ package org.emergya.backtrackTSP; import java.util.ArrayList; import java.util.List; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.TimeUnit; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.gofleet.openLS.tsp.TSPAlgorithm; import org.gofleet.openLS.tsp.TSPStop; import org.gofleet.openLS.tsp.TSPStopBag; public class BackTrackingTSP implements TSPAlgorithm { private static Log LOG = LogFactory.getLog(BackTrackingTSP.class); private Boolean partialSolution = false; private Integer seconds = 18; private ExecutorService executor; private ExecutorService executor2; public BackTrackingTSP() { } /** * If we cannot find a solution, do you like to get the best partial * solution reached? * * @param partialSolution */ public BackTrackingTSP(Boolean partialSolution, Integer seconds) { this(); if (partialSolution != null) this.partialSolution = partialSolution; this.seconds = seconds; } public List<TSPStop> order(TSPStopBag _bag) { long time = System.currentTimeMillis(); Runtime runtime = Runtime.getRuntime(); int numthreads = runtime.availableProcessors() * 10; executor = Executors.newFixedThreadPool(numthreads); DistanceMatrix distances = new DistanceMatrix(); initializeMatrix(distances, _bag); SolutionContainer solutions = new SolutionContainer(distances); if (_bag.size() > 7) { if (_bag.hasLast()) { // run(executor, new AStar(_bag, distances, solutions)); run(executor, new HeuristicBacktracking(_bag, distances, solutions)); } else { for (TSPStop stop : _bag.getAll()) { List<TSPStop> stops = new ArrayList<TSPStop>(); stops.addAll(_bag.getAll()); stops.remove(stop); BacktrackStopBag bag = new BacktrackStopBag(stops, _bag.getFirst(), stop); // run(executor, new AStar(bag, distances, solutions)); run(executor, new HeuristicBacktracking(bag, distances, solutions)); } } } run(executor, new Backtracking(_bag, distances, solutions)); executor.shutdown(); try { if (!executor.awaitTermination(this.seconds - (System.currentTimeMillis() - time) / 1000, TimeUnit.SECONDS)) { stop(); } } catch (InterruptedException e) { if (!this.partialSolution) { throw new RuntimeException("Timeout reached. I couldn't find a solution on a proper time. " + "Please, give me another chance with more time or" + " accept a partial solution. I won't fail you, I promise.", e); } } return getBest(solutions, distances, _bag.size()); } private void run(final ExecutorService executor, final Runnable aStar) { executor.execute(aStar); } private List<TSPStop> getBest(SolutionContainer solutions, DistanceMatrix distances, Integer size) { BackTrackSolution solution = solutions.getSolution(); if (solution == null) throw new RuntimeException("I'm embarrased, I was unable to find a solution for you. " + "Please, forgive me. I am just a machine."); return solution.getStack(); } /** * Initialices the distance matrix on background while tsp is running. * * @param distances * @param bag */ private void initializeMatrix(DistanceMatrix distances, TSPStopBag bag) { Runtime runtime = Runtime.getRuntime(); int numthreads = runtime.availableProcessors() * 3; executor2 = Executors.newFixedThreadPool(numthreads); List<BacktrackStop> candidates = null; candidates = new ArrayList<BacktrackStop>(); for (TSPStop stop : bag.getAll()) candidates.add((BacktrackStop) stop); for (BacktrackStop from : candidates) { executor2.execute(new InitializeDistances(from, candidates, distances)); } executor2.shutdown(); Thread t = new Thread() { @Override public void run() { try { executor2.awaitTermination(6, TimeUnit.SECONDS); } catch (InterruptedException e) { LOG.error(e, e); } } }; t.start(); } @Override public boolean stop() { LOG.info("Shutting down backtracking"); if (executor2 != null) executor2.shutdownNow(); if (executor != null) executor.shutdownNow(); else return false; LOG.info("Backtracking shut down"); return true; } } class SolutionContainer { private BackTrackSolution solution = null; private DistanceMatrix distances = null; public SolutionContainer(DistanceMatrix distances) { this.distances = distances; } public BackTrackSolution getSolution() { synchronized (this) { return this.solution; } } public void add(BackTrackSolution solution) { synchronized (this) { if (this.solution == null) this.solution = solution; else { if (this.solution.getDistance(distances) > solution.getDistance(distances)) this.solution = solution; } } } }