Package org.apache.commons.math4.legacy.genetics

Class 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

    • Method Detail

      • 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

      • 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