Package org.apache.commons.rng.sampling

Class SubsetSamplerUtils

  • final class SubsetSamplerUtils
extends java.lang.Object
    Utility class for selecting a subset of a sequence of integers.

    • Constructor Summary

      Constructors 
      Modifier Constructor Description
      private SubsetSamplerUtils()
      No public construction.

    • Method Summary

      All Methods Static Methods Concrete Methods 
      Modifier and Type Method Description
      (package private) static void checkSubset​(int n, int k)
      Checks the subset of length k from n is valid.
      (package private) static int[] partialSample​(int[] domain, int steps, UniformRandomProvider rng, boolean upper)
      Perform a partial Fisher-Yates shuffle of the domain in-place and return either the upper fully shuffled section or the remaining lower partially shuffled section.
      (package private) static void swap​(int[] array, int i, int j)
      Swaps the two specified elements in the specified array.

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Constructor Detail

      • SubsetSamplerUtils

        private SubsetSamplerUtils()
        No public construction.

    • Method Detail

      • checkSubset

        static void checkSubset​(int n,
                        int k)
        Checks the subset of length k from n is valid.

        If n <= 0 or k <= 0 or k > n then no subset is required and an exception is raised.

        Parameters:
        n - Size of the set.
        k - Size of the subset.
        Throws:
        java.lang.IllegalArgumentException - if n <= 0 or k <= 0 or k > n.

      • partialSample

        static int[] partialSample​(int[] domain,
                           int steps,
                           UniformRandomProvider rng,
                           boolean upper)
        Perform a partial Fisher-Yates shuffle of the domain in-place and return either the upper fully shuffled section or the remaining lower partially shuffled section.

        The returned combination will have a length of steps for upper=true, or domain.length - steps otherwise.

        Sampling uses UniformRandomProvider.nextInt(int).

        Parameters:
        domain - The domain.
        steps - The number of shuffle steps.
        rng - Generator of uniformly distributed random numbers.
        upper - Set to true to return the upper fully shuffled section.
        Returns:
        a random combination.

      • swap

        static void swap​(int[] array,
                 int i,
                 int j)
        Swaps the two specified elements in the specified array.
        Parameters:
        array - the array
        i - the first index
        j - the second index