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Update to the swap-bits mutator. True changes are now preferred.

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This commit is contained in:
Marcel Kronfeld 2010-11-11 11:09:23 +00:00
parent 2873df5058
commit 68c25a6c53
1 changed files with 36 additions and 4 deletions
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40
src/eva2/server/go/operators/mutation/MutateGASwapBits.java
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@ -10,20 +10,25 @@ import eva2.server.go.problems.InterfaceOptimizationProblem;
import eva2.tools.math.RNG;
/**
* Created by IntelliJ IDEA.
* User: streiche
* Swap two random bits of a GA individual. If preferPairs is true, unequal pairs
* are picked with some preference (by trying for l/2 times, where l is the binary
* individual length).
*
* User: streiche, mkron
* Date: 05.08.2004
* Time: 17:45:36
* To change this template use File | Settings | File Templates.
*/
public class MutateGASwapBits implements InterfaceMutation, java.io.Serializable {
private int m_NumberOfMutations = 1;
private boolean preferPairs = true; // if true, pairs of (1,0) are swapped with higher probability
public MutateGASwapBits() {
}
public MutateGASwapBits(MutateGASwapBits mutator) {
this.m_NumberOfMutations = mutator.m_NumberOfMutations;
this.setPreferTrueChange(mutator.isPreferTrueChange());
}
/** This method will enable you to clone a given mutation operator
@ -73,8 +78,8 @@ public class MutateGASwapBits implements InterfaceMutation, java.io.Serializable
int[][] mutationIndices = new int[this.m_NumberOfMutations][2];
boolean tmpBit;
for (int i = 0; i < mutationIndices.length; i++) {
mutationIndices[i][0] = RNG.randomInt(0, ((InterfaceGAIndividual)individual).getGenotypeLength());;
mutationIndices[i][1] = RNG.randomInt(0, ((InterfaceGAIndividual)individual).getGenotypeLength());;
mutationIndices[i][0] = getRandomIndex(individual, true); // may prefer true bits
mutationIndices[i][1] = getRandomIndex(individual, false); // may prefer false bits
}
// double instances of mutationIndices could be checked here... *sigh*
for (int i = 0; i < mutationIndices.length; i++) {
@ -87,6 +92,24 @@ public class MutateGASwapBits implements InterfaceMutation, java.io.Serializable
//System.out.println("After Mutate: " +((GAIndividual)individual).getSolutionRepresentationFor());
}
private int getRandomIndex(AbstractEAIndividual individual, boolean maybePrefered) {
int genoLen = ((InterfaceGAIndividual)individual).getGenotypeLength();
int k = RNG.randomInt(0, genoLen);
if (isPreferTrueChange()) {
int maxTries=genoLen/2;
while (!(maybePrefered==((InterfaceGAIndividual)individual).getBGenotype().get(k)) && (maxTries>=0)) {
k=(k+RNG.randomInt(1,genoLen))%genoLen; // try next random position
maxTries--;
}
}
return k;
}
// private int getRandomSecondIndex(int firstIndex, AbstractEAIndividual individual) {
// int genoLen = ((InterfaceGAIndividual)individual).getGenotypeLength();
// return RNG.randomInt(0, genoLen);
// }
/** This method allows you to get a string representation of the mutation
* operator
* @return A descriptive string.
@ -126,4 +149,13 @@ public class MutateGASwapBits implements InterfaceMutation, java.io.Serializable
public String numberOfMutationsTipText() {
return "The number of bits to be swapped.";
}
public void setPreferTrueChange(boolean preferPairs) {
this.preferPairs = preferPairs;
}
public boolean isPreferTrueChange() {
return preferPairs;
}
public String preferTrueChangeTipText() {
return "If set to true, mutation events will prefer swapping 1 and 0";
}
}