aco/environment/Environment.java

   1 package aco.environment;
   2
   3 import java.lang.Runtime;
   4 import java.util.SortedMap;
   5 import java.util.Observable;
   6
   7 import aco.ant.*;
   8 import aco.misc.*;
   9 import aco.mediator.*;
  10 import aco.environment.data.*;
  11
  12 public class Environment
  13   extends Observable {
  14
  15   protected Ant[] ants;
  16   protected ACOMediator acom;
  17   protected EnvironmentData ed;
  18
  19   public Environment(ACOMediator acom) {
  20     this.acom = acom;
  21
  22     this.ants = new Ant[acom.getNumOfAnts()];
  23
  24     for (int i = 0; i < acom.getNumOfAnts(); i++)
  25       ants[i] = new Ant(acom);
  26
  27     this.ed = new EnvironmentData(acom);
  28
  29     /* add a shutdown hook to print out the last best solution */
  30     Runtime.getRuntime().addShutdownHook(new EnvironmentShutdownHook(this));
  31
  32     /* run the garbage collector after all the initialization is done */
  33     System.gc();
  34   }
  35
  36   /* d'tor */
  37   protected void finalize() {
  38     deleteObservers();
  39   }
  40
  41   public void run() {
  42     int i = 0;
  43     while (! terminateCondition(i++)) {
  44       constructSolutions();
  45       updateStatistics(i);
  46       acom.pheromoneUpdate(ants);
  47       /* localSearch();
  48        * updatePheromoneTrails(); */
  49     }
  50   }
  51
  52   protected void constructSolutions() {
  53
  54     /* clear ants memory and ..
  55      * assign an initial random city to ant */
  56     /* TODO: threading */
  57     for (Ant ant : ants) {
  58       ant.reset();
  59       acom.pickInitialRandomCity(ant);
  60     }
  61
  62     /* let each ant construct a complete tour
  63      * start a 1 since every ant already has an initial city */
  64     /* TODO: threading */
  65     for (int step = 1; step < acom.getNumOfCities(); step++) {
  66       for (Ant ant : ants)
  67         acom.neighbourListASDecisionRule(ant, step);
  68     }
  69
  70     /* compute tour length of each ant */
  71     /* TODO: threading */
  72     for (Ant ant : ants) {
  73       acom.computeTourLength(ant);
  74     }
  75
  76
  77   }
  78
  79   protected void updateStatistics(int iteration) {
  80     for (Ant ant : ants) {
  81
  82       if (ant.getTourLength() < acom.getGlobalBestTourLength()) {
  83         acom.setGlobalBestTourLength(ant.getTourLength());
  84         acom.setGlobalBestTourIteration(iteration);
  85
  86         for (int i = 0; i < acom.getNumOfCities() + 1; i++) {
  87           acom.setGlobalBestTour(i, ant.getTour(i));
  88         }
  89
  90         acom.addGlobalBestTour((Integer)acom.getGlobalBestTourLength(),
  91             acom.getGlobalBestTour());
  92         this.setChanged();
  93         this.notifyObservers();
  94       }
  95
  96     }
  97
  98     /* since we are already at it.. run the garbage collector */
  99     System.gc();
 100   }
 101
 102   /*
 103   protected boolean stagnationBehaviour() {
 104     for (Ant antOne : ants) {
 105       for (Ant antTwo : ants) {
 106         for (int i : antOne.getTour()) {
 107           for (int j : antTwo.getTour()) {
 108             if (i != j)
 109               return false;
 110           }
 111         }
 112       }
 113     }
 114     return true;
 115   }
 116   */
 117
 118   protected boolean terminateCondition(int iteration) {
 119     /* 1) solution within predefined distance
 120      * 2) max number of tour constructions or algorithm iterations
 121      * 3) max cpu time
 122      * 4) algorithm stagnation behaviour */
 123     if (iteration >= acom.getMaxNumOfTours()) {
 124       return true;
 125     //} else if (stagnationBehaviour()) {
 126       //return true;
 127     } else {
 128       return false;
 129     }
 130   }
 131
 132   @Override
 133     public String toString() {
 134       StringBuilder result = new StringBuilder();
 135
 136       result.append("Shortest tour at iteration " +
 137           acom.getGlobalBestTourIteration() +
 138           " with length " +
 139           acom.getGlobalBestTourLength() +
 140           "\n");
 141
 142       for (int t : acom.getGlobalBestTour())
 143           result.append(t + " -- ");
 144
 145       result.delete(result.lastIndexOf(" -- "), result.length());
 146       return result.toString();
 147     }
 148
 149   public int[] getGlobalBestTour() {
 150     return ed.getGlobalBestTour();
 151   }
 152
 153   public int getGlobalBestTour(int index) {
 154     return ed.getGlobalBestTour(index);
 155   }
 156
 157   public void setGlobalBestTour(int[] GlobalBestTour) {
 158     ed.setGlobalBestTour(GlobalBestTour);
 159   }
 160
 161   public void setGlobalBestTour(int index, int GlobalBestTour) {
 162     ed.setGlobalBestTour(index, GlobalBestTour);
 163   }
 164
 165   public int getGlobalBestTourLength() {
 166     return ed.getGlobalBestTourLength();
 167   }
 168
 169   public void setGlobalBestTourLength(int GlobalBestTourLength) {
 170     ed.setGlobalBestTourLength(GlobalBestTourLength);
 171   }
 172
 173   public int getGlobalBestTourIteration() {
 174     return ed.getGlobalBestTourIteration();
 175   }
 176
 177   public void setGlobalBestTourIteration(int GlobalBestTourIteration) {
 178     ed.setGlobalBestTourIteration(GlobalBestTourIteration);
 179   }
 180
 181   public SortedMap<Integer, int[]> getGlobalBestTourMap() {
 182     return ed.getGlobalBestTourMap();
 183   }
 184
 185   public void addGlobalBestTour(Integer TourLength, int[] Tour) {
 186     ed.addGlobalBestTour(TourLength, Tour);
 187   }
 188
 189 }