| 1 | /*
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| 2 | Copyright 2006 by Sean Luke
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| 3 | Licensed under the Academic Free License version 3.0
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| 4 | See the file "LICENSE" for more information
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| 5 | */
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| 6 |
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| 7 |
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| 8 | package ec.app.tutorial3;
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| 9 | import ec.*;
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| 10 | import ec.util.*;
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| 11 |
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| 12 | public class OurSelection extends SelectionMethod
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| 13 | {
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| 14 | // We have to specify a default base
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| 15 | public static final String P_OURSELECTION = "our-selection";
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| 16 | public Parameter defaultBase() { return new Parameter(P_OURSELECTION); }
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| 17 |
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| 18 | public static final String P_MIDDLEPROBABILITY = "middle-probability"; // our parameter name
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| 19 |
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| 20 | public double middleProbability;
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| 21 |
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| 22 | public void setup(final EvolutionState state, final Parameter base)
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| 23 | {
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| 24 | super.setup(state,base); // always call super.setup(...) first if it exists!
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| 25 |
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| 26 | Parameter def = defaultBase();
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| 27 |
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| 28 | // gets a double between min (0.0) and max (1.0), from the parameter
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| 29 | // database, returning a value of min-1 (-1.0) if the parameter doesn't exist or was
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| 30 | // outside this range.
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| 31 | middleProbability = state.parameters.getDoubleWithMax(base.push(P_MIDDLEPROBABILITY),
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| 32 | def.push(P_MIDDLEPROBABILITY),0.0,1.0);
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| 33 | if (middleProbability < 0.0)
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| 34 | state.output.fatal("Middle-Probability must be between 0.0 and 1.0",
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| 35 | base.push(P_MIDDLEPROBABILITY),def.push(P_MIDDLEPROBABILITY));
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| 36 | }
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| 37 |
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| 38 | public int produce(final int subpopulation, final EvolutionState state, final int thread)
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| 39 | {
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| 40 | //toss a coin
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| 41 | if (state.random[thread].nextBoolean(middleProbability))
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| 42 | {
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| 43 | //pick three individuals, return the middle one
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| 44 | Individual[] inds = state.population.subpops[subpopulation].individuals;
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| 45 | int one = state.random[thread].nextInt(inds.length);
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| 46 | int two = state.random[thread].nextInt(inds.length);
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| 47 | int three = state.random[thread].nextInt(inds.length);
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| 48 | // generally the betterThan(...) method imposes an ordering,
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| 49 | // so you shouldn't see any cycles here except in very unusual domains...
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| 50 | if (inds[two].fitness.betterThan(inds[one].fitness))
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| 51 | {
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| 52 | if (inds[three].fitness.betterThan(inds[two].fitness)) // 1 < 2 < 3
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| 53 | return two;
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| 54 | else if (inds[three].fitness.betterThan(inds[one].fitness)) // 1 < 3 < 2
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| 55 | return three;
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| 56 | else // 3 < 1 < 2
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| 57 | return one;
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| 58 | }
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| 59 | else if (inds[three].fitness.betterThan(inds[one].fitness)) // 2 < 1 < 3
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| 60 | return one;
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| 61 | else if (inds[three].fitness.betterThan(inds[two].fitness)) // 2 < 3 < 1
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| 62 | return three;
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| 63 | else // 3 < 2 < 1
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| 64 | return two;
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| 65 | }
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| 66 | else //select a random individual's index
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| 67 | {
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| 68 | return state.random[thread].nextInt(
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| 69 | state.population.subpops[subpopulation].individuals.length);
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| 70 | }
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| 71 | }
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| 72 | } // close the class
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