Package cern.jet.random.sampling

Class RandomSamplingAssistant

  • All Implemented Interfaces:
    java.io.Serializable, java.lang.Cloneable
    public class RandomSamplingAssistant
extends PersistentObject
    Conveniently computes a stable Simple Random Sample Without Replacement (SRSWOR) subsequence of n elements from a given input sequence of N elements; Example: Computing a sublist of n=3 random elements from a list (1,...,50) may yield the sublist (7,13,47). The subsequence is guaranteed to be stable, i.e. elements never change position relative to each other. Each element from the N elements has the same probability to be included in the n chosen elements. This class is a convenience adapter for RandomSampler using blocks.
    Version:
    1.0, 02/05/99
    See Also:
    RandomSampler, Serialized Form

    • Constructor Summary

      Constructors 
      Constructor Description
      RandomSamplingAssistant​(long n, long N, RandomEngine randomGenerator)
      Constructs a random sampler that samples n random elements from an input sequence of N elements.

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      java.lang.Object clone()
      Returns a deep copy of the receiver.
      protected void fetchNextBlock()
      Not yet commented.
      RandomEngine getRandomGenerator()
      Returns the used random generator.
      static void main​(java.lang.String[] args)
      Tests random sampling.
      static int[] sampleArray​(int n, int[] elements)
      Just shows how this class can be used; samples n elements from and int[] array.
      boolean sampleNextElement()
      Returns whether the next element of the input sequence shall be sampled (picked) or not.
      static void test​(long n, long N)
      Tests the methods of this class.
      static void testArraySampling​(int n, int N)
      Tests the methods of this class.
      private void xsampleNextElements​(BooleanArrayList acceptList)
      Returns whether the next elements of the input sequence shall be sampled (picked) or not.

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • buffer

        protected long[] buffer

      • bufferPosition

        protected int bufferPosition

      • skip

        protected long skip

      • n

        protected long n

    • Constructor Detail

      • RandomSamplingAssistant

        public RandomSamplingAssistant​(long n,
                               long N,
                               RandomEngine randomGenerator)
        Constructs a random sampler that samples n random elements from an input sequence of N elements.
        Parameters:
        n - the total number of elements to choose (must be >= 0).
        N - number of elements to choose from (must be >= n).
        randomGenerator - a random number generator. Set this parameter to null to use the default random number generator.

    • Method Detail

      • clone

        public java.lang.Object clone()
        Returns a deep copy of the receiver.
        Overrides:
        clone in class PersistentObject
        Returns:
        a copy of the receiver.

      • fetchNextBlock

        protected void fetchNextBlock()
        Not yet commented.

      • getRandomGenerator

        public RandomEngine getRandomGenerator()
        Returns the used random generator.

      • main

        public static void main​(java.lang.String[] args)
        Tests random sampling.

      • sampleArray

        public static int[] sampleArray​(int n,
                                int[] elements)
        Just shows how this class can be used; samples n elements from and int[] array.

      • sampleNextElement

        public boolean sampleNextElement()
        Returns whether the next element of the input sequence shall be sampled (picked) or not.
        Returns:
        true if the next element shall be sampled (picked), false otherwise.

      • test

        public static void test​(long n,
                        long N)
        Tests the methods of this class. To do benchmarking, comment the lines printing stuff to the console.

      • testArraySampling

        public static void testArraySampling​(int n,
                                     int N)
        Tests the methods of this class. To do benchmarking, comment the lines printing stuff to the console.

      • xsampleNextElements

        private void xsampleNextElements​(BooleanArrayList acceptList)
        Returns whether the next elements of the input sequence shall be sampled (picked) or not. one is chosen from the first block, one from the second, ..., one from the last block.
        Parameters:
        acceptList - a bitvector which will be filled with true where sampling shall occur and false where it shall not occur.