org.apache.mahout.math.jet.random.engine

Class RandomEngine

java.lang.Object

org.apache.mahout.math.function.DoubleFunction

org.apache.mahout.math.jet.random.engine.RandomEngine

All Implemented Interfaces:

IntFunction

Direct Known Subclasses:

MersenneTwister

public abstract class RandomEngine
extends DoubleFunction
implements IntFunction

Abstract base class for uniform pseudo-random number generating engines.

Most probability distributions are obtained by using a uniform pseudo-random number generation engine followed by a transformation to the desired distribution. Thus, subclasses of this class are at the core of computational statistics, simulations, Monte Carlo methods, etc.

Subclasses produce uniformly distributed int's and long's in the closed intervals [Integer.MIN_VALUE,Integer.MAX_VALUE] and [Long.MIN_VALUE,Long.MAX_VALUE], respectively, as well as float's and double's in the open unit intervals (0.0f,1.0f) and (0.0,1.0), respectively.

Subclasses need to override one single method only: nextInt(). All other methods generating different data types or ranges are usually layered upon nextInt(). long's are formed by concatenating two 32 bit int's. float's are formed by dividing the interval [0.0f,1.0f] into 2³² sub intervals, then randomly choosing one subinterval. double's are formed by dividing the interval [0.0,1.0] into 2⁶⁴ sub intervals, then randomly choosing one subinterval.

Note that this implementation is not synchronized.

See Also:

MersenneTwister, Random

Constructor Summary

Constructors

Constructor and Description
RandomEngine()

Method Summary

Methods

Modifier and Type	Method and Description
double	apply(double dummy) Equivalent to raw().
int	apply(int dummy) Equivalent to nextInt().
double	nextDouble()
float	nextFloat()
abstract int	nextInt()
long	nextLong()
double	raw()

Methods inherited from class org.apache.mahout.math.function.DoubleFunction

isDensifying

Methods inherited from class java.lang.Object

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

Constructor Detail

RandomEngine

public RandomEngine()

Method Detail

apply

public double apply(double dummy)

Equivalent to raw(). This has the effect that random engines can now be used as function objects, returning a random number upon function evaluation.

Specified by:

apply in class DoubleFunction

Parameters:

dummy - double for the argument

Returns:

the result of applying the function

apply

public int apply(int dummy)

Equivalent to nextInt(). This has the effect that random engines can now be used as function objects, returning a random number upon function evaluation.

Specified by:

apply in interface IntFunction

Parameters:

dummy - argument passed to the function.

Returns:

the result of the function.

nextDouble

public double nextDouble()

Returns:

a 64 bit uniformly distributed random number in the open unit interval (0.0,1.0) (excluding 0.0 and 1.0).

nextFloat

public float nextFloat()

Returns:

a 32 bit uniformly distributed random number in the open unit interval (0.0f, 1.0f) (excluding 0.0f and 1.0f).

nextInt

public abstract int nextInt()

Returns:

a 32 bit uniformly distributed random number in the closed interval [Integer.MIN_VALUE,Integer.MAX_VALUE] (including Integer.MIN_VALUE and Integer.MAX_VALUE);

nextLong

public long nextLong()

Returns:

a 64 bit uniformly distributed random number in the closed interval [Long.MIN_VALUE,Long.MAX_VALUE] (including Long.MIN_VALUE and Long.MAX_VALUE).

raw

public double raw()

Returns:

a 32 bit uniformly distributed random number in the open unit interval (0.0, 1.0) (excluding 0.0 and 1.0).