Mercurial > hg > de.mpg.mpiwg.itgroup.digilib.plugin
view libs/commons-math-2.1/docs/apidocs/src-html/org/apache/commons/math/genetics/TournamentSelection.html @ 13:cbf34dd4d7e6
commons-math-2.1 added
| author | dwinter |
|---|---|
| date | Tue, 04 Jan 2011 10:02:07 +0100 |
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<HTML> <BODY BGCOLOR="white"> <PRE> <FONT color="green">001</FONT> /*<a name="line.1"></a> <FONT color="green">002</FONT> * Licensed to the Apache Software Foundation (ASF) under one or more<a name="line.2"></a> <FONT color="green">003</FONT> * contributor license agreements. See the NOTICE file distributed with<a name="line.3"></a> <FONT color="green">004</FONT> * this work for additional information regarding copyright ownership.<a name="line.4"></a> <FONT color="green">005</FONT> * The ASF licenses this file to You under the Apache License, Version 2.0<a name="line.5"></a> <FONT color="green">006</FONT> * (the "License"); you may not use this file except in compliance with<a name="line.6"></a> <FONT color="green">007</FONT> * the License. You may obtain a copy of the License at<a name="line.7"></a> <FONT color="green">008</FONT> *<a name="line.8"></a> <FONT color="green">009</FONT> * http://www.apache.org/licenses/LICENSE-2.0<a name="line.9"></a> <FONT color="green">010</FONT> *<a name="line.10"></a> <FONT color="green">011</FONT> * Unless required by applicable law or agreed to in writing, software<a name="line.11"></a> <FONT color="green">012</FONT> * distributed under the License is distributed on an "AS IS" BASIS,<a name="line.12"></a> <FONT color="green">013</FONT> * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.<a name="line.13"></a> <FONT color="green">014</FONT> * See the License for the specific language governing permissions and<a name="line.14"></a> <FONT color="green">015</FONT> * limitations under the License.<a name="line.15"></a> <FONT color="green">016</FONT> */<a name="line.16"></a> <FONT color="green">017</FONT> package org.apache.commons.math.genetics;<a name="line.17"></a> <FONT color="green">018</FONT> <a name="line.18"></a> <FONT color="green">019</FONT> import java.util.ArrayList;<a name="line.19"></a> <FONT color="green">020</FONT> import java.util.List;<a name="line.20"></a> <FONT color="green">021</FONT> <a name="line.21"></a> <FONT color="green">022</FONT> /**<a name="line.22"></a> <FONT color="green">023</FONT> * Tournament selection scheme. Each of the two selected chromosomes is selected<a name="line.23"></a> <FONT color="green">024</FONT> * based on n-ary tournament -- this is done by drawing {@link #arity} random<a name="line.24"></a> <FONT color="green">025</FONT> * chromosomes without replacement from the population, and then selecting the<a name="line.25"></a> <FONT color="green">026</FONT> * fittest chromosome among them.<a name="line.26"></a> <FONT color="green">027</FONT> *<a name="line.27"></a> <FONT color="green">028</FONT> * @since 2.0<a name="line.28"></a> <FONT color="green">029</FONT> * @version $Revision: 811685 $ $Date: 2009-09-05 13:36:48 -0400 (Sat, 05 Sep 2009) $<a name="line.29"></a> <FONT color="green">030</FONT> */<a name="line.30"></a> <FONT color="green">031</FONT> public class TournamentSelection implements SelectionPolicy {<a name="line.31"></a> <FONT color="green">032</FONT> <a name="line.32"></a> <FONT color="green">033</FONT> /** number of chromosomes included in the tournament selections */<a name="line.33"></a> <FONT color="green">034</FONT> private int arity;<a name="line.34"></a> <FONT color="green">035</FONT> <a name="line.35"></a> <FONT color="green">036</FONT> /**<a name="line.36"></a> <FONT color="green">037</FONT> * Creates a new TournamentSelection instance.<a name="line.37"></a> <FONT color="green">038</FONT> *<a name="line.38"></a> <FONT color="green">039</FONT> * @param arity<a name="line.39"></a> <FONT color="green">040</FONT> * how many chromosomes will be drawn to the tournament<a name="line.40"></a> <FONT color="green">041</FONT> */<a name="line.41"></a> <FONT color="green">042</FONT> public TournamentSelection(int arity) {<a name="line.42"></a> <FONT color="green">043</FONT> this.arity = arity;<a name="line.43"></a> <FONT color="green">044</FONT> }<a name="line.44"></a> <FONT color="green">045</FONT> <a name="line.45"></a> <FONT color="green">046</FONT> /**<a name="line.46"></a> <FONT color="green">047</FONT> * Select two chromosomes from the population. Each of the two selected<a name="line.47"></a> <FONT color="green">048</FONT> * chromosomes is selected based on n-ary tournament -- this is done by<a name="line.48"></a> <FONT color="green">049</FONT> * drawing {@link #arity} random chromosomes without replacement from the<a name="line.49"></a> <FONT color="green">050</FONT> * population, and then selecting the fittest chromosome among them.<a name="line.50"></a> <FONT color="green">051</FONT> *<a name="line.51"></a> <FONT color="green">052</FONT> * @param population<a name="line.52"></a> <FONT color="green">053</FONT> * the population from which the chromosomes are choosen.<a name="line.53"></a> <FONT color="green">054</FONT> * @return the selected chromosomes.<a name="line.54"></a> <FONT color="green">055</FONT> */<a name="line.55"></a> <FONT color="green">056</FONT> public ChromosomePair select(Population population) {<a name="line.56"></a> <FONT color="green">057</FONT> return new ChromosomePair(<a name="line.57"></a> <FONT color="green">058</FONT> tournament((ListPopulation) population),<a name="line.58"></a> <FONT color="green">059</FONT> tournament((ListPopulation)population)<a name="line.59"></a> <FONT color="green">060</FONT> );<a name="line.60"></a> <FONT color="green">061</FONT> }<a name="line.61"></a> <FONT color="green">062</FONT> <a name="line.62"></a> <FONT color="green">063</FONT> /**<a name="line.63"></a> <FONT color="green">064</FONT> * Helper for {@link #select(Population)}. Draw {@link #arity} random<a name="line.64"></a> <FONT color="green">065</FONT> * chromosomes without replacement from the population, and then select the<a name="line.65"></a> <FONT color="green">066</FONT> * fittest chromosome among them.<a name="line.66"></a> <FONT color="green">067</FONT> *<a name="line.67"></a> <FONT color="green">068</FONT> * @param population<a name="line.68"></a> <FONT color="green">069</FONT> * the population from which the chromosomes are choosen.<a name="line.69"></a> <FONT color="green">070</FONT> * @return the selected chromosome.<a name="line.70"></a> <FONT color="green">071</FONT> */<a name="line.71"></a> <FONT color="green">072</FONT> private Chromosome tournament(ListPopulation population) {<a name="line.72"></a> <FONT color="green">073</FONT> if (population.getPopulationSize() < this.arity)<a name="line.73"></a> <FONT color="green">074</FONT> throw new IllegalArgumentException("Tournament arity cannot be bigger than population size.");<a name="line.74"></a> <FONT color="green">075</FONT> // auxiliary population<a name="line.75"></a> <FONT color="green">076</FONT> ListPopulation tournamentPopulation = new ListPopulation(this.arity) {<a name="line.76"></a> <FONT color="green">077</FONT> public Population nextGeneration() {<a name="line.77"></a> <FONT color="green">078</FONT> // not useful here<a name="line.78"></a> <FONT color="green">079</FONT> return null;<a name="line.79"></a> <FONT color="green">080</FONT> }<a name="line.80"></a> <FONT color="green">081</FONT> };<a name="line.81"></a> <FONT color="green">082</FONT> <a name="line.82"></a> <FONT color="green">083</FONT> // create a copy of the chromosome list<a name="line.83"></a> <FONT color="green">084</FONT> List<Chromosome> chromosomes = new ArrayList<Chromosome> (population.getChromosomes());<a name="line.84"></a> <FONT color="green">085</FONT> for (int i=0; i<this.arity; i++) {<a name="line.85"></a> <FONT color="green">086</FONT> // select a random individual and add it to the tournament<a name="line.86"></a> <FONT color="green">087</FONT> int rind = GeneticAlgorithm.getRandomGenerator().nextInt(chromosomes.size());<a name="line.87"></a> <FONT color="green">088</FONT> tournamentPopulation.addChromosome(chromosomes.get(rind));<a name="line.88"></a> <FONT color="green">089</FONT> // do not select it again<a name="line.89"></a> <FONT color="green">090</FONT> chromosomes.remove(rind);<a name="line.90"></a> <FONT color="green">091</FONT> }<a name="line.91"></a> <FONT color="green">092</FONT> // the winner takes it all<a name="line.92"></a> <FONT color="green">093</FONT> return tournamentPopulation.getFittestChromosome();<a name="line.93"></a> <FONT color="green">094</FONT> }<a name="line.94"></a> <FONT color="green">095</FONT> <a name="line.95"></a> <FONT color="green">096</FONT> /**<a name="line.96"></a> <FONT color="green">097</FONT> * Gets the arity (number of chromosomes drawn to the tournament).<a name="line.97"></a> <FONT color="green">098</FONT> *<a name="line.98"></a> <FONT color="green">099</FONT> * @return arity of the tournament<a name="line.99"></a> <FONT color="green">100</FONT> */<a name="line.100"></a> <FONT color="green">101</FONT> public int getArity() {<a name="line.101"></a> <FONT color="green">102</FONT> return arity;<a name="line.102"></a> <FONT color="green">103</FONT> }<a name="line.103"></a> <FONT color="green">104</FONT> <a name="line.104"></a> <FONT color="green">105</FONT> /**<a name="line.105"></a> <FONT color="green">106</FONT> * Sets the arity (number of chromosomes drawn to the tournament).<a name="line.106"></a> <FONT color="green">107</FONT> *<a name="line.107"></a> <FONT color="green">108</FONT> * @param arity arity of the tournament<a name="line.108"></a> <FONT color="green">109</FONT> */<a name="line.109"></a> <FONT color="green">110</FONT> public void setArity(int arity) {<a name="line.110"></a> <FONT color="green">111</FONT> this.arity = arity;<a name="line.111"></a> <FONT color="green">112</FONT> }<a name="line.112"></a> <FONT color="green">113</FONT> <a name="line.113"></a> <FONT color="green">114</FONT> }<a name="line.114"></a> </PRE> </BODY> </HTML>