Package io.jenetics.engine

Class Codecs

  • public final class Codecs
extends Object
    This class contains factory methods for creating common problem encodings.
    Since:
    3.2
    Version:
    5.2

    • Method Detail

      • ofScalar

        public static <A> Codec<A,​AnyGene<A>> ofScalar​(Supplier<? extends A> supplier,
                                                     Predicate<? super A> validator)
        Return a scala Codec with the given allele Supplier and allele validator. The supplier is responsible for creating new random alleles, and the validator can verify it.

        The following example shows a codec which creates and verifies BigInteger objects.

        final Codec<BigInteger, AnyGene<BigInteger>> codec = Codecs.of( // Create new random 'BigInteger' object. () -> { final byte[] data = new byte[100]; RandomRegistry.getRandom().nextBytes(data); return new BigInteger(data); }, // Verify that bit 7 is set. (For illustration purpose.) bi -> bi.testBit(7) );
        Type Parameters:
        A - the allele type
        Parameters:
        supplier - the allele-supplier which is used for creating new, random alleles
        validator - the validator used for validating the created gene. This predicate is used in the AnyGene.isValid() method.
        Returns:
        a new Codec with the given parameters
        Throws:
        NullPointerException - if one of the parameters is null
        See Also:
        AnyGene.of(Supplier, Predicate), AnyChromosome.of(Supplier, Predicate)

      • ofVector

        public static <A> Codec<ISeq<A>,​AnyGene<A>> ofVector​(Supplier<? extends A> supplier,
                                                           Predicate<? super A> alleleValidator,
                                                           Predicate<? super ISeq<A>> alleleSeqValidator,
                                                           int length)
        Return a scala Codec with the given allele Supplier, allele validator and Chromosome length. The supplier is responsible for creating new random alleles, and the validator can verify it.

        The following example shows a codec which creates and verifies BigInteger object arrays.

        final Codec<BigInteger[], AnyGene<BigInteger>> codec = Codecs.of( // Create new random 'BigInteger' object. () -> { final byte[] data = new byte[100]; RandomRegistry.getRandom().nextBytes(data); return new BigInteger(data); }, // Verify that bit 7 is set. (For illustration purpose.) bi -> bi.testBit(7), // The 'Chromosome' length. 123 );
        Type Parameters:
        A - the allele type
        Parameters:
        supplier - the allele-supplier which is used for creating new, random alleles
        alleleValidator - the validator used for validating the created gene. This predicate is used in the AnyGene.isValid() method.
        alleleSeqValidator - the validator used for validating the created chromosome. This predicate is used in the AnyChromosome.isValid() method.
        length - the vector length
        Returns:
        a new Codec with the given parameters
        Throws:
        NullPointerException - if one of the parameters is null
        IllegalArgumentException - if the length of the vector is smaller than one.
        See Also:
        AnyChromosome.of(Supplier, Predicate, Predicate, int)

      • ofVector

        public static <A> Codec<ISeq<A>,​AnyGene<A>> ofVector​(Supplier<? extends A> supplier,
                                                           Predicate<? super A> validator,
                                                           int length)
        Return a scala Codec with the given allele Supplier, allele validator and Chromosome length. The supplier is responsible for creating new random alleles, and the validator can verify it.
        Type Parameters:
        A - the allele type
        Parameters:
        supplier - the allele-supplier which is used for creating new, random alleles
        validator - the validator used for validating the created gene. This predicate is used in the AnyGene.isValid() method.
        length - the vector length
        Returns:
        a new Codec with the given parameters
        Throws:
        NullPointerException - if one of the parameters is null
        IllegalArgumentException - if the length of the vector is smaller than one.

      • ofVector

        public static <A> Codec<ISeq<A>,​AnyGene<A>> ofVector​(Supplier<? extends A> supplier,
                                                           int length)
        Return a scala Codec with the given allele Supplier and Chromosome length. The supplier is responsible for creating new random alleles.
        Type Parameters:
        A - the allele type
        Parameters:
        supplier - the allele-supplier which is used for creating new, random alleles
        length - the vector length
        Returns:
        a new Codec with the given parameters
        Throws:
        NullPointerException - if one of the parameters is null
        IllegalArgumentException - if the length of the vector is smaller than one.

      • ofMatrix

        public static InvertibleCodec<int[][],​IntegerGene> ofMatrix​(IntRange domain,
                                                                  int rows,
                                                                  int cols)
        Return a 2-dimensional matrix InvertibleCodec for the given range. All matrix values are restricted by the same domain. The dimension of the returned matrix is int[rows][cols].
        Parameters:
        domain - the domain of the matrix values
        rows - the number of rows of the matrix
        cols - the number of columns of the matrix
        Returns:
        a new matrix Codec
        Throws:
        NullPointerException - if the given domain is null
        IllegalArgumentException - if the rows or cols are smaller than one.
        Since:
        4.4

      • ofMatrix

        public static InvertibleCodec<long[][],​LongGene> ofMatrix​(LongRange domain,
                                                                int rows,
                                                                int cols)
        Return a 2-dimensional matrix InvertibleCodec for the given range. All matrix values are restricted by the same domain. The dimension of the returned matrix is long[rows][cols].
        Parameters:
        domain - the domain of the matrix values
        rows - the number of rows of the matrix
        cols - the number of columns of the matrix
        Returns:
        a new matrix Codec
        Throws:
        NullPointerException - if the given domain is null
        IllegalArgumentException - if the rows or cols are smaller than one.
        Since:
        4.4

      • ofMatrix

        public static InvertibleCodec<double[][],​DoubleGene> ofMatrix​(DoubleRange domain,
                                                                    int rows,
                                                                    int cols)
        Return a 2-dimensional matrix InvertibleCodec for the given range. All matrix values are restricted by the same domain. The dimension of the returned matrix is double[rows][cols].
        Parameters:
        domain - the domain of the matrix values
        rows - the number of rows of the matrix
        cols - the number of columns of the matrix
        Returns:
        a new matrix Codec
        Throws:
        NullPointerException - if the given domain is null
        IllegalArgumentException - if the rows or cols are smaller than one.
        Since:
        4.4

      • ofMapping

        public static <A,​B,​M extends Map<A,​B>> InvertibleCodec<M,​EnumGene<Integer>> ofMapping​(ISeq<? extends A> source,
                                                                                                              ISeq<? extends B> target,
                                                                                                              Supplier<M> mapSupplier)
        Create a codec, which creates a a mapping from the elements given in the source sequence to the elements given in the target sequence. The returned mapping can be seen as a function which maps every element of the target set to an element of the source set.
        final ISeq<Integer> numbers = ISeq.of(1, 2, 3, 4, 5); final ISeq<String> strings = ISeq.of("1", "2", "3"); final Codec<Map<Integer, String>, EnumGene<Integer>> codec = Codecs.ofMapping(numbers, strings, HashMap::new);
        If source.size() > target.size(), the created mapping is surjective, if source.size() < target.size(), the mapping is injective and if both sets have the same size, the returned mapping is bijective.
        Type Parameters:
        A - the type of the source elements
        B - the type of the target elements
        M - the type of the encoded Map
        Parameters:
        source - the source elements. Will be the keys of the encoded Map.
        target - the target elements. Will be the values of the encoded Map.
        mapSupplier - a function which returns a new, empty Map into which the mapping will be inserted
        Returns:
        a new mapping codec
        Throws:
        IllegalArgumentException - if the target sequences are empty
        NullPointerException - if one of the argument is null
        Since:
        4.3

      • ofMapping

        public static <A,​B> InvertibleCodec<Map<A,​B>,​EnumGene<Integer>> ofMapping​(ISeq<? extends A> source,
                                                                                            ISeq<? extends B> target)
        Create a codec, which creates a a mapping from the elements given in the source sequence to the elements given in the target sequence. The returned mapping can be seen as a function which maps every element of the target set to an element of the source set.
        final ISeq<Integer> numbers = ISeq.of(1, 2, 3, 4, 5); final ISeq<String> strings = ISeq.of("1", "2", "3"); final Codec<Map<Integer, String>, EnumGene<Integer>> codec = Codecs.ofMapping(numbers, strings);
        If source.size() > target.size(), the created mapping is surjective, if source.size() < target.size(), the mapping is injective and if both sets have the same size, the returned mapping is bijective.
        Type Parameters:
        A - the type of the source elements
        B - the type of the target elements
        Parameters:
        source - the source elements. Will be the keys of the encoded Map.
        target - the target elements. Will be the values of the encoded Map.
        Returns:
        a new mapping codec
        Throws:
        IllegalArgumentException - if the target sequences are empty
        NullPointerException - if one of the argument is null
        Since:
        4.3

      • ofSubSet

        public static <T> InvertibleCodec<ISeq<T>,​BitGene> ofSubSet​(ISeq<? extends T> basicSet)
        The subset InvertibleCodec can be used for problems where it is required to find the best variable-sized subset from given basic set. A typical usage example of the returned Codec is the Knapsack problem.

        The following code snippet shows a simplified variation of the Knapsack problem.

        public final class Main { // The basic set from where to choose an 'optimal' subset. private final static ISeq<Integer> SET = ISeq.of(1, 2, 3, 4, 5, 6, 7, 8, 9, 10); // Fitness function directly takes an 'int' value. private static int fitness(final ISeq<Integer> subset) { assert(subset.size() <= SET.size()); final int size = subset.stream() .collect(Collectors.summingInt(Integer::intValue)); return size <= 20 ? size : 0; } public static void main(final String[] args) { final Engine<BitGene, Double> engine = Engine .builder(Main::fitness, codec.ofSubSet(SET)) .build(); ... } }
        Type Parameters:
        T - the element type of the basic set
        Parameters:
        basicSet - the basic set, from where to choose the optimal subset.
        Returns:
        a new codec which can be used for modelling subset problems.
        Throws:
        NullPointerException - if the given basicSet is null; null elements are allowed.
        IllegalArgumentException - if the basicSet size is smaller than one.

      • ofSubSet

        public static <T> InvertibleCodec<ISeq<T>,​EnumGene<T>> ofSubSet​(ISeq<? extends T> basicSet,
                                                                      int size)
        The subset InvertibleCodec can be used for problems where it is required to find the best fixed-size subset from given basic set.
        Type Parameters:
        T - the element type of the basic set
        Parameters:
        basicSet - the basic set, from where to choose the optimal subset.
        size - the length of the desired subsets
        Returns:
        a new codec which can be used for modelling subset problems.
        Throws:
        NullPointerException - if the given basicSet is null; null elements are allowed.
        IllegalArgumentException - if basicSet.size() < size, size <= 0 or basicSet.size()*size will cause an integer overflow.
        Since:
        3.4
        See Also:
        PermutationChromosome, PermutationChromosome.of(ISeq, int)