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Java > Open Source Codes > org > jgap > impl > fitness > TruthTableFitnessFunction


1 /*
2  * This file is part of JGAP.
3  *
4  * JGAP offers a dual license model containing the LGPL as well as the MPL.
5  *
6  * For licencing information please see the file license.txt included with JGAP
7  * or have a look at the top of class org.jgap.Chromosome which representatively
8  * includes the JGAP license policy applicable for any file delivered with JGAP.
9  */
10 package org.jgap.impl.fitness;
11
12 import java.util.*;
13 import org.jgap.*;
14
15 /**
16  * Fitness Function relying on a truth table.
17  * <p>
18  * To use this class, just implement a subclass of it, register the current
19  * truth table and implement the evaluate method in a way that you can call
20  * calcFitness with the required (parameter (given values: encoded with the
21  * chromosome). If the truth table is dynamic just register it in evaluate,
22  * otherwise do it after construction of this fitness function.
23  *
24  * @author Klaus Meffert
25  * @since 2.4
26  */
27 public abstract class TruthTableFitnessFunction
28     extends FitnessFunction {
29   /** String containing the CVS revision. Read out via reflection!*/
30   private final static String JavaDoc CVS_REVISION = "$Revision: 1.5 $";
31
32   private Map m_truthTable;
33
34   // Constants for calculating the fitness value
35 // -------------------------------------------
36 public static final int MAX_FITNESS = 9999999;
37
38   private static final int RELATION_FITNESS = 100;
39
40   public static final int WORST = MAX_FITNESS / RELATION_FITNESS;
41
42   private Configuration m_conf;
43
44   /**
45    * Only use for dynamic instantiation as configuration retrieved from static
46    * setting.
47    *
48    * @author Klaus Meffert
49    * @since 2.4
50    */
51   public TruthTableFitnessFunction() {
52     this(Genotype.getStaticConfiguration());
53   }
54
55   /**
56    * Constructor without registering a truth table. Use this constructor if the
57    * truth table is not fix over generations and needs to be set in method
58    * evaluate.
59    *
60    * @param a_conf the configuration to use
61    *
62    * @author Klaus Meffert
63    * @since 3.01
64    */
65   public TruthTableFitnessFunction(Configuration a_conf) {
66     m_conf = a_conf;
67   }
68
69
70   /**
71    * Constructor for registering a truth table. Use this constructor if the
72    * truth table is fix over generations.
73    *
74    * @param a_conf the configuration to use
75    * @param a_truthTable table of input/output pairs for feeding the formula
76    * and determining the fitness value thru delta computation
77    *
78    * @author Klaus Meffert
79    * @since 3.1
80    */
81   public TruthTableFitnessFunction(Configuration a_conf, final Map a_truthTable) {
82     this(a_conf);
83     setTruthTable(a_truthTable);
84   }
85
86   public void setTruthTable(final Map a_truthTable) {
87     m_truthTable = a_truthTable;
88   }
89
90   public Map getTruthTable() {
91     return m_truthTable;
92   }
93
94   /**
95    * Implementation of the evaluate method from class FitnessFunction.
96    * Calculates the fitness of a given Chromosome in a determined way.
97    * @param a_chromosome the Chromosome to be evaluated
98    * @return positive integer value representing the fitness of the Chromosome
99    *
100    * @author Klaus Meffert
101    * @since 2.4
102    */
103   protected abstract double evaluate(IChromosome a_chromosome);
104
105   /**
106    * Fitness value calculation for a given table of input/output tupels
107    * and a truth-table (also given as list of input/output tupels)
108    *
109    * @param a_actualInputOutput table of actual input/output pairs
110    * @return delta between current values and given truth table
111    *
112    * @author Klaus Meffert
113    * @since 2.4
114    */
115   public double calcFitness(final Map a_actualInputOutput) {
116     // Determine delta values of all function values and add up their squares
117 double outputValueGiven, outputValueWanted;
118     Double JavaDoc inputValueWanted;
119     double diffAbs = 0.0f;
120     double delta;
121     double deltaAbs;
122     Set keySet = getTruthTable().keySet();
123     Iterator keys = keySet.iterator();
124     while (keys.hasNext()) {
125       inputValueWanted = (Double JavaDoc) keys.next();
126       outputValueWanted = ( (Double JavaDoc) getTruthTable().get(inputValueWanted)).
127           doubleValue();
128       Double JavaDoc output = ( (Double JavaDoc) a_actualInputOutput.get(inputValueWanted));
129       if (output != null) {
130         outputValueGiven = output.doubleValue();
131         // determine current value (evolved formula) minus reference value
132 if (Double.isNaN(outputValueWanted)) {
133           return Double.NaN;
134         }
135         delta = outputValueGiven - outputValueWanted;
136         deltaAbs = (float) Math.abs(delta);
137       }
138       else {
139         deltaAbs = Math.abs(outputValueWanted);
140       }
141       diffAbs += deltaAbs;
142     }
143     /**@todo consider length of formula (i.e. number of terms, e.g.) for
144      * fitness calculation*/
145
146     return diffAbs;
147   }
148
149   /**
150    * @return the Configuration object set
151    *
152    * @author Klaus Meffert
153    * @since 3.1
154    */
155   public Configuration getConfiguration() {
156     return m_conf;
157   }
158 }
159
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