aco/strategy/ACOStrategy.java

   1 package aco.strategy;
   2
   3 import aco.ant.*;
   4 import aco.mediator.*;
   5
   6 public abstract class ACOStrategy {
   7
   8   protected ACOMediator acom;
   9
  10   public ACOStrategy(ACOMediator acom) {
  11     this.acom = acom;
  12   }
  13
  14   public void computeTourLength(Ant ant) {
  15     ant.setTour(acom.getNumOfCities(), ant.getTour(0));
  16     for (int i = 0; i < acom.getNumOfCities(); i++) {
  17       /* tourlength = tourlength + distance(i, i+1) */
  18       ant.setTourLength(
  19           ant.getTourLength() +
  20           acom.getDistance(ant.getTour(i), ant.getTour(i+1)));
  21     }
  22   }
  23
  24   public void pickInitialRandomCity(Ant ant) {
  25     int r = (int)(Math.random() * acom.getNumOfCities());
  26     ant.setTour(0, r);
  27     ant.setVisited(r, true);
  28   }
  29
  30   public abstract void neighbourListASDecisionRule(Ant ant, int Step);
  31
  32   protected void chooseBestNext(Ant ant, int Step) {
  33     int nc = 0;
  34     /* this seems to be neccessary because some choice information
  35      * tends to become zero after a while */
  36     double v = -1.0;
  37     int CurrentCity = ant.getTour(Step - 1);
  38
  39     for (int j = 0; j < acom.getNumOfCities(); j++) {
  40       if (! ant.getVisited(j)) {
  41         if (acom.getChoiceInformation(CurrentCity,j) > v) {
  42           nc = j;
  43           v = acom.getChoiceInformation(CurrentCity,j);
  44         }
  45       }
  46     }
  47
  48     ant.setTour(Step, nc);
  49     ant.setVisited(nc, true);
  50   }
  51
  52 }