Module io.jenetics.base
Package io.jenetics.engine

Interface Problem<T,G extends Gene<?,G>,C extends Comparable<? super C>>

Type Parameters:
T - the (native) argument type of the problem fitness function
G - the gene type the evolution engine is working with
C - the result type of the fitness function
All Known Implementing Classes:
Regression
public interface Problem<T,G extends Gene<?,G>,C extends Comparable<? super C>>
This interface describes a problem which can be solved by the GA evolution Engine. It connects the actual fitness() function and the needed codec(). 
final Problem<ISeq<BitGene>, BitGene, Integer> counting = Problem.of(
    // Native fitness function
    genes -> (int)genes.stream()
        .filter(BitGene::bit)
        .count(),
    // Problem encoding
    Codec.of(
        Genotype.of(BitChromosome.of(100)),
        gt -> ISeq.of(gt.chromosome())
    )
);
The example above shows the Ones-Counting problem definition.
Since:
3.4
Version:
6.1
See Also:

  • Method Summary

    Modifier and Type
    Method
    Description
    Codec<T,G>
    codec()
    Return the codec, which translates the types of the problem domain into types, which can be understood by the evolution Engine.
    default Optional<Constraint<G,C>>
    constraint()
    Return the constraint, associated with this problem, if available.
    default T
    decode(Genotype<G> genotype)
    Converts the given Genotype to the target type Problem.
    Function<T,C>
    fitness()
    Return the fitness function of the problem in the native problem domain.
    default C
    fitness(Genotype<G> genotype)
    Returns the fitness value for the given argument.
    default C
    fitness(T arg)
    Returns the fitness value for the given argument.
    static <T, G extends Gene<?, G>, C extends Comparable<? super C>>
    Problem<T,G,C>
    of(Function<T,C> fitness, Codec<T,G> codec)
    Return a new optimization problem with the given parameters.
    static <T, G extends Gene<?, G>, C extends Comparable<? super C>>
    Problem<T,G,C>
    of(Function<T,C> fitness, Codec<T,G> codec, Constraint<G,C> constraint)
    Return a new optimization problem with the given parameters.

  • Method Details

    • fitness

      Function<T,C> fitness()
      Return the fitness function of the problem in the native problem domain.
      Returns:
      the fitness function

    • codec

      Codec<T,G> codec()
      Return the codec, which translates the types of the problem domain into types, which can be understood by the evolution Engine.
      Returns:
      the engine codec

    • constraint

      default Optional<Constraint<G,C>> constraint()
      Return the constraint, associated with this problem, if available.
      Returns:
      the constraint, associated with this problem
      Since:
      6.1

    • decode

      default T decode(Genotype<G> genotype)
      Converts the given Genotype to the target type Problem. This is a shortcut for 
      final Problem<SomeObject, DoubleGene, Double> problem = ...;
final Genotype<DoubleGene> gt = problem.codec().encoding().newInstance();

final SomeObject arg = problem.decode(gt);
      Parameters:
      genotype - the genotype to be converted
      Returns:
      the converted genotype
      Throws:
      NullPointerException - if the given genotype is null
      Since:
      4.2
      See Also:

    • fitness

      default C fitness(T arg)
      Returns the fitness value for the given argument.
      Parameters:
      arg - the argument of the fitness function
      Returns:
      the fitness value
      Since:
      4.1

    • fitness

      default C fitness(Genotype<G> genotype)
      Returns the fitness value for the given argument.
      Parameters:
      genotype - the argument of the fitness function
      Returns:
      the fitness value
      Since:
      4.1

    • of

      static <T, G extends Gene<?, G>, C extends Comparable<? super C>> Problem<T,G,C> of(Function<T,C> fitness, Codec<T,G> codec, Constraint<G,C> constraint)
      Return a new optimization problem with the given parameters. The given constraint is applied to the Engine, via Engine.Builder.constraint(Constraint), and the Codec, via Constraint.constrain(Codec).

      Note
      When creating a new Problem instance with this factory method, there is no need for additionally constraining the given codec with Constraint.constrain(Codec).

      Type Parameters:
      T - the (native) argument type of the problem fitness function
      G - the gene type the evolution engine is working with
      C - the result type of the fitness function
      Parameters:
      fitness - the problem fitness function
      codec - the evolution engine codec
      constraint - the problem constraint, may be null
      Returns:
      a new problem object from the given parameters
      Throws:
      NullPointerException - if the fitness or codec is null
      Since:
      6.1
      See Also:

    • of

      static <T, G extends Gene<?, G>, C extends Comparable<? super C>> Problem<T,G,C> of(Function<T,C> fitness, Codec<T,G> codec)
      Return a new optimization problem with the given parameters.
      Type Parameters:
      T - the (native) argument type of the problem fitness function
      G - the gene type the evolution engine is working with
      C - the result type of the fitness function
      Parameters:
      fitness - the problem fitness function
      codec - the evolution engine codec
      Returns:
      a new problem object from the given parameters
      Throws:
      NullPointerException - if one of the arguments is null