edu.cornell.lassp.houle.RngPack

Class RandomElement

java.lang.Object

edu.cornell.lassp.houle.RngPack.RandomElement

All Implemented Interfaces:

java.lang.Cloneable

Direct Known Subclasses:

RandomJava, RandomSeedable, RandomShuffle, RandomSynchronized

public abstract class RandomElement
extends java.lang.Object
implements java.lang.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.

See Also:

RandomJava, RandomShuffle

Constructor Summary

Constructors

Constructor and Description
RandomElement()

Method Summary

Modifier and Type	Method and Description
int	choose(int hi)
int	choose(int lo, int hi)
java.lang.Object	clone()
boolean	coin()
boolean	coin(double p)
double	gaussian() gaussian() uses the Box-Muller algorithm to transform raw()'s into gaussian deviates.
double	gaussian(double sd)
double	powlaw(double alpha, double cut) generate a power-law distribution with exponent alpha and lower cutoff cut
abstract double	raw() The abstract method that must be defined to make a working RandomElement.
void	raw(double[] d) Fill an entire array with doubles.
void	raw(double[] d, int n) Fill part or all of an array with doubles.
double	uniform(double lo, double hi)

Methods inherited from class java.lang.Object

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

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

clone

public java.lang.Object clone()
                       throws java.lang.CloneNotSupportedException

Overrides:

clone in class java.lang.Object

Throws:

java.lang.CloneNotSupportedException