Package org.apache.commons.math3.genetics

Class RandomKey<T>

java.lang.Object
org.apache.commons.math3.genetics.Chromosome
org.apache.commons.math3.genetics.AbstractListChromosome<Double>
org.apache.commons.math3.genetics.RandomKey<T>
Type Parameters:
T - type of the permuted objects
All Implemented Interfaces:
Comparable<Chromosome>, Fitness, PermutationChromosome<T>
public abstract class RandomKey<T> extends AbstractListChromosome<Double> implements PermutationChromosome<T>
Random Key chromosome is used for permutation representation. It is a vector of a fixed length of real numbers in [0,1] interval. The index of the i-th smallest value in the vector represents an i-th member of the permutation.

For example, the random key [0.2, 0.3, 0.8, 0.1] corresponds to the permutation of indices (3,0,1,2). If the original (unpermuted) sequence would be (a,b,c,d), this would mean the sequence (d,a,b,c).

With this representation, common operators like n-point crossover can be used, because any such chromosome represents a valid permutation.

Since the chromosome (and thus its arrayRepresentation) is immutable, the array representation is sorted only once in the constructor.

For details, see:

  • Bean, J.C.: Genetic algorithms and random keys for sequencing and optimization. ORSA Journal on Computing 6 (1994) 154-160
  • Rothlauf, F.: Representations for Genetic and Evolutionary Algorithms. Volume 104 of Studies in Fuzziness and Soft Computing. Physica-Verlag, Heidelberg (2002)
Since:
2.0

  • Constructor Details

  • Method Details

    • decode

      public List<T> decode(List<T> sequence)
      Permutes the sequence of objects of type T according to the permutation this chromosome represents. For example, if this chromosome represents a permutation (3,0,1,2), and the unpermuted sequence is (a,b,c,d), this yields (d,a,b,c).
      Specified by:
      decode in interface PermutationChromosome<T>
      Parameters:
      sequence - the unpermuted (original) sequence of objects
      Returns:
      permutation of sequence represented by this permutation

    • isSame

      protected boolean isSame(Chromosome another)
      Returns true iff another is a RandomKey and encodes the same permutation.
      Overrides:
      isSame in class Chromosome
      Parameters:
      another - chromosome to compare
      Returns:
      true iff chromosomes encode the same permutation

    • checkValidity

      protected void checkValidity(List<Double> chromosomeRepresentation) throws InvalidRepresentationException
      Asserts that representation can represent a valid chromosome.
      Specified by:
      checkValidity in class AbstractListChromosome<Double>
      Parameters:
      chromosomeRepresentation - representation of the chromosome
      Throws:
      InvalidRepresentationException - iff the representation can not represent a valid chromosome

    • randomPermutation

      public static final List<Double> randomPermutation(int l)
      Generates a representation corresponding to a random permutation of length l which can be passed to the RandomKey constructor.
      Parameters:
      l - length of the permutation
      Returns:
      representation of a random permutation

    • identityPermutation

      public static final List<Double> identityPermutation(int l)
      Generates a representation corresponding to an identity permutation of length l which can be passed to the RandomKey constructor.
      Parameters:
      l - length of the permutation
      Returns:
      representation of an identity permutation

    • comparatorPermutation

      public static <S> List<Double> comparatorPermutation(List<S> data, Comparator<S> comparator)
      Generates a representation of a permutation corresponding to the data sorted by comparator. The data is not modified during the process. This is useful if you want to inject some permutations to the initial population.
      Type Parameters:
      S - type of the data
      Parameters:
      data - list of data determining the order
      comparator - how the data will be compared
      Returns:
      list representation of the permutation corresponding to the parameters

    • inducedPermutation

      public static <S> List<Double> inducedPermutation(List<S> originalData, List<S> permutedData) throws DimensionMismatchException, MathIllegalArgumentException
      Generates a representation of a permutation corresponding to a permutation which yields permutedData when applied to originalData. This method can be viewed as an inverse to decode(List).
      Type Parameters:
      S - type of the data
      Parameters:
      originalData - the original, unpermuted data
      permutedData - the data, somehow permuted
      Returns:
      representation of a permutation corresponding to the permutation originalData -> permutedData
      Throws:
      DimensionMismatchException - iff the length of originalData and permutedData lists are not equal
      MathIllegalArgumentException - iff the permutedData and originalData lists contain different data

    • toString

      public String toString()
      Overrides:
      toString in class AbstractListChromosome<Double>