Package io.jenetics.prog.regression

Interface Complexity<T>

  • Type Parameters:
    T - the sample type
    Functional Interface:
    This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.
    @FunctionalInterface
public interface Complexity<T>
    Represents a complexity measure if a given program tree. The program complexity ensures, that simpler programs with similar loss function values are preferred. It is part of the overall Error function.
    final Error<Double> error = Error.of(LossFunction::mse, Complexity.ofMaxNodeCount(50));
    Since:
    5.0
    Version:
    5.0
    Author:
    Franz Wilhelmstötter
    See Also:
    LossFunction, Error

    • Method Summary

      All Methods Static Methods Instance Methods Abstract Methods 
      Modifier and Type Method Description
      double apply​(Tree<? extends Op<T>,​?> program)
      Calculates the complexity of the current program (possibly) relative to the actual error value.
      static double count​(Tree<?,​?> program, int maxNodes)
      This method uses the node count of a program tree for calculating its complexity.
      static <T> Complexity<T> ofNodeCount​(int maxNodeCount)
      Return a complexity measure which counts the number of nodes of a program.

    • Method Detail

      • apply

        double apply​(Tree<? extends Op<T>,​?> program)
        Calculates the complexity of the current program (possibly) relative to the actual error value.
        Parameters:
        program - the actual program
        Returns:
        the measure of the program complexity

      • ofNodeCount

        static <T> Complexity<T> ofNodeCount​(int maxNodeCount)
        Return a complexity measure which counts the number of nodes of a program.
        Type Parameters:
        T - the sample type
        Parameters:
        maxNodeCount - the maximal node count. The returned complexity will be one if the program node count is greater or equal the given count
        Returns:
        a program node count complexity measure
        Throws:
        IllegalArgumentException - if the max node count is smaller than one
        See Also:
        count(Tree, int)

      • count

        static double count​(Tree<?,​?> program,
                    int maxNodes)
        This method uses the node count of a program tree for calculating its complexity. The returned node count measure is within the range of [0, 1]. If the program contains only one node, zero is returned. If the node count is bigger or equal maxNodes, one is returned.

        The complexity is calculated in the following way:

        final double cc = min(program.size() - 1, maxNodes); return 1.0 - sqrt(1.0 - (cc*cc)/(maxNodes*maxNodes));
        Parameters:
        program - the program used for the complexity measure
        maxNodes - the maximal expected node count
        Returns:
        the complexity measure of the given program
        Throws:
        NullPointerException - if the given program is null
        IllegalArgumentException - if maxNodes is smaller than one
        See Also:
        ofNodeCount(int)