aco/strategy/eas/EASPheromoneStrategy.java

   1 package aco.strategy.eas;
   2
   3 import aco.ant.*;
   4 import aco.strategy.*;
   5 import aco.mediator.*;
   6 import aco.mediator.eas.*;
   7
   8 public class EASPheromoneStrategy
   9   extends PheromoneStrategy {
  10
  11   protected EASMediator acom;
  12
  13   public EASPheromoneStrategy(ACOMediator acom) {
  14     super(acom);
  15   }
  16
  17   public void pheromoneUpdate(Ant[] ants) {
  18     this.evaporate();
  19
  20     for (Ant ant : ants) {
  21       this.depositPheromone(ant);
  22     }
  23
  24     enforceGlobalBest();
  25
  26     acom.computeChoiceInformation();
  27   }
  28
  29   protected void enforceGlobalBest() {
  30     /* enforcement of global best route */
  31     int j = 0, l = 0;
  32     for (int i = 0; i < acom.getNumOfCities(); i++) {
  33       j = acom.getGlobalBestTour(i);
  34       l = acom.getGlobalBestTour(i+1);
  35       acom.setPheromone( j, l, (acom.getPheromone(j,l) +
  36             acom.getE()/(double)acom.getGlobalBestTourLength()) );
  37     }
  38   }
  39
  40   protected void depositPheromone(Ant ant) {
  41     double dt = 1.0/(double)ant.getTourLength();
  42     int j = 0;
  43     int l = 0;
  44     for (int i = 0; i < acom.getNumOfCities(); i++) {
  45       j = ant.getTour(i);
  46       l = ant.getTour(i+1);
  47       /* setPheromone will update j,l and l,j */
  48       acom.setPheromone( j, l, (acom.getPheromone(j,l) + dt) );
  49     }
  50   }
  51
  52   protected void evaporate() {
  53     for (int i = 1; i < acom.getNumOfCities(); i++) {
  54       for (int j = 1; j < acom.getNumOfCities(); j++) {
  55         acom.setPheromone(i, j,
  56             (1.0 - acom.getRoh()) * acom.getPheromone(i, j) );
  57       }
  58     }
  59   }
  60
  61 }