RandomStreamBase Class Reference

This class provides a convenient foundation on which RNGs can be built. More...

Inheritance diagram for RandomStreamBase:

Collaboration diagram for RandomStreamBase:

Public Member Functions
abstract void	resetStartStream ()
	Reinitializes the stream to its initial state \(I_g\): \(C_g\) and \(B_g\) are set to \(I_g\).
abstract void	resetStartSubstream ()
	Reinitializes the stream to the beginning of its current substream: \(C_g\) is set to \(B_g\).
abstract void	resetNextSubstream ()
	Reinitializes the stream to the beginning of its next substream: \(N_g\) is computed, and \(C_g\) and \(B_g\) are set to \(N_g\).
abstract String	toString ()
	Returns a string containing the current state of this stream. More...
void	increasedPrecision (boolean incp)
	After calling this method with incp = true, each call to the RNG (direct or indirect) for this stream will return a uniform random number with more bits of precision than what is returned by nextValue, and will advance the state of the stream by 2 steps instead of 1 (i.e., nextValue will be called twice for each random number). More...
double	nextDouble ()
	Returns a uniform random number between 0 and 1 from the stream. More...
void	nextArrayOfDouble (double[] u, int start, int n)
	Calls nextDouble n times to fill the array u. More...
int	nextInt (int i, int j)
	Calls nextDouble once to create one integer between i and j. More...
void	nextArrayOfInt (int i, int j, int[] u, int start, int n)
	Calls nextInt n times to fill the array u. More...
String	formatState ()
	Use the toString method.
String	formatStateFull ()
	Use the toStringFull method.
RandomStreamBase	clone ()
	Clones the current generator and return its copy. More...

Protected Member Functions
abstract double	nextValue ()
	This method should return the next random number (between 0 and 1) from the current stream. More...

Protected Attributes
String	name = null
boolean	prec53 = false
boolean	anti = false

Static Protected Attributes
static double	invtwo24 = 5.9604644775390625e-8

Detailed Description

This class provides a convenient foundation on which RNGs can be built.

It implements all the methods which do not depend directly on the generator itself, but only on its output, which is to be defined by implementing the abstract method nextValue. In the present class, all methods returning random numbers directly or indirectly (nextDouble, nextArrayOfDouble, nextInt and nextArrayOfInt) call nextValue. Thus, to define a subclass that implements a RNG, it suffices to implement nextValue, in addition to the reset... and toString methods. Of course, the other methods may also be overridden for improved efficiency.

If the nextValue already generates numbers with a precision of 53-bits or higher, then nextDouble can be overridden to improve the performance. The mechanism for increasing the precision assumes that nextValue returns at least 29 bits of precision, in which case the higher precision numbers will have roughly 52 bits of precision. This mechanism was designed primarily for RNGs that return numbers with around 30 to 32 bits of precision.

RandomStreamBase and its subclasses are implementing the Serializable interface. Each class has a serial number wich represent the class version. For instance 70510 means that the last change was the 10th May 2007.

Member Function Documentation

clone()

RandomStreamBase clone

(

)

Clones the current generator and return its copy.

Returns

A deep copy of the current generator

Implements CloneableRandomStream.

increasedPrecision()

void increasedPrecision

(

boolean

incp

)

After calling this method with incp = true, each call to the RNG (direct or indirect) for this stream will return a uniform random number with more bits of precision than what is returned by nextValue, and will advance the state of the stream by 2 steps instead of 1 (i.e., nextValue will be called twice for each random number).

More precisely, if s is a stream of a subclass of RandomStreamBase, when the precision has been increased, the instruction "<tt>u = s.nextDouble()</tt>", is equivalent to "<tt>u = (s.nextValue() + s.nextValue()*fact) % 1.0</tt>" where the constant fact is equal to \(2^{-24}\). This also applies when calling nextDouble indirectly (e.g., via nextInt, etc.). By default, or if this method is called again with incp = false, each call to nextDouble for this stream advances the state by 1 step and returns the same number as nextValue.

Parameters

incp	if the generator will be set to high precision mode

nextArrayOfDouble()

void nextArrayOfDouble	(	double []	u,
		int	start,
		int	n
	)

Calls nextDouble n times to fill the array u.

Parameters

u	the array in which the numbers will be stored
start	the first index of u to be used
n	the number of random numbers to put in u

Implements RandomStream.

nextArrayOfInt()

void nextArrayOfInt	(	int	i,
		int	j,
		int []	u,
		int	start,
		int	n
	)

Calls nextInt n times to fill the array u.

This method should be overridden if a faster implementation exists for the specific generator.

Parameters

i	the smallest possible integer to put in u
j	the largest possible integer to put in u
u	the array in which the numbers will be stored
start	the first index of u to be used
n	the number of random numbers to put in u

Implements RandomStream.

nextDouble()

double nextDouble

(

)

Returns a uniform random number between 0 and 1 from the stream.

Its behavior depends on the last call to increasedPrecision. The generators programmed in SSJ never return the values 0 or 1.

Returns

a number in the interval (0,1)

Implements RandomStream.

nextInt()

int nextInt	(	int	i,
		int	j
	)

Calls nextDouble once to create one integer between i and j.

This method always uses the highest order bits of the random number. It should be overridden if a faster implementation exists for the specific generator.

Parameters

i	the smallest possible returned integer
j	the largest possible returned integer

Returns

a random integer between i and j

Implements RandomStream.

nextValue()

abstract double nextValue ( )

abstractprotected

This method should return the next random number (between 0 and 1) from the current stream.

If the stream is set to the high precision mode (increasedPrecision(true) was called), then each call to nextDouble will call nextValue twice, otherwise it will call it only once.

Returns

a number in the interval (0,1)

toString()

abstract String toString ( )

abstract

Returns a string containing the current state of this stream.

Returns

the state of the generator formated as a string

Implements RandomStream.

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The documentation for this class was generated from the following file:

• RandomStreamBase.java