Package edu.cornell.lassp.houle.RngPack

Class RandomElement

  • All Implemented Interfaces:
    Cloneable
    Direct Known Subclasses:
    RandomSeedable
    public abstract class RandomElement
extends Object
implements Cloneable
    RandomElement is an abstract class that encapsulates random number generators. To base a class on it, you must define the method raw() as described below. It is also likely that you will want to define a constructor or another mechanism for seeding the the generator. The other classes defined in RandomElement add value to the numbers generated by raw()

    Source code is available.

    Version:
    1.1a
    Author:
    Paul Houle (E-mail: paul@honeylocust.com)
    See Also:
    RandomJava, RandomShuffle

    • Constructor Detail

      • RandomElement

        public RandomElement()

    • Method Detail

      • raw

        public abstract double raw()
        The abstract method that must be defined to make a working RandomElement. See the class RandomJava for an example of how to do this.
        Returns:
        a random double in the range [0,1]
        See Also:
        RandomJava

      • raw

        public void raw​(double[] d,
                int n)
        Fill part or all of an array with doubles. The method defined here uses multiple calls to raw() to fill the array. You can eliminate the overhead of multiple method calls by subclassing this with a version of the generator that fills the array. On our system this improves the efficiency of Ranecu by 20% when filling large arrays.
        Parameters:
        d - array to be filled with doubles
        n - number of doubles to generate

      • raw

        public void raw​(double[] d)
        Fill an entire array with doubles. This method calls raw(double d[],int n) with d=d.length. Since this adds little overhead for d.length large, it is only necessary to override raw(double d[],int n)
        Parameters:
        d - array to be filled with doubles.

      • choose

        public int choose​(int hi)
        Parameters:
        hi - upper limit of range
        Returns:
        a random integer in the range 1,2,... ,hi

      • choose

        public int choose​(int lo,
                  int hi)
        Parameters:
        lo - lower limit of range
        hi - upper limit of range
        Returns:
        a random integer in the range lo, lo+1, ... ,hi

      • coin

        public boolean coin()
        Returns:
        a boolean that's true 0.5 of the time; equivalent to coin(0.5).

      • coin

        public boolean coin​(double p)
        Parameters:
        p - probability that function will return true
        Returns:
        a boolean that's true p of the time.

      • uniform

        public double uniform​(double lo,
                      double hi)
        Parameters:
        lo - lower limit of range
        hi - upper limit of range
        Returns:
        a uniform random real in the range [lo,hi]

      • gaussian

        public double gaussian()
        gaussian() uses the Box-Muller algorithm to transform raw()'s into gaussian deviates.
        Returns:
        a random real with a gaussian distribution, standard deviation

      • gaussian

        public double gaussian​(double sd)
        Parameters:
        sd - standard deviation
        Returns:
        a gaussian distributed random real with standard deviation sd

      • powlaw

        public double powlaw​(double alpha,
                     double cut)
        generate a power-law distribution with exponent alpha and lower cutoff cut
        Parameters:
        alpha - the exponent
        cut - the lower cutoff