This class represents a random stream whose uniforms are cached for more efficiency when using common random numbers. More...

Inheritance diagram for RandomStreamWithCache:

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Collaboration diagram for RandomStreamWithCache:

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Public Member Functions
	RandomStreamWithCache (RandomStream stream)
	Constructs a new cached random stream with internal stream `stream`. More...

	RandomStreamWithCache (RandomStream stream, int initialCapacity)
	Constructs a new cached random stream with internal stream `stream`. More...

boolean	isCaching ()
	Determines if the random stream is caching values, default being `true`. More...

void	setCaching (boolean caching)
	Sets the caching indicator to `caching`. More...

RandomStream	getCachedStream ()
	Returns a reference to the random stream whose values are cached. More...

void	setCachedStream (RandomStream stream)
	Sets the random stream whose values are cached to `stream`. More...

void	clearCache ()
	Clears the cached values for this random stream. More...

void	initCache ()
	Resets this random stream to recover values from the cache. More...

int	getNumCachedValues ()
	Returns the total number of values cached by this random stream. More...

int	getCacheIndex ()
	Return the index of the next cached value that will be returned by the stream. More...

void	setCacheIndex (int newIndex)
	Sets the index, in the cache, of the next value returned by nextDouble. More...

DoubleArrayList	getCachedValues ()
	Returns an array list containing the values cached by this random stream. More...

void	setCachedValues (DoubleArrayList values)
	Sets the array list containing the cached values to `values`. More...

void	resetStartStream ()
	Reinitializes the stream to its initial state \(I_g\): \(C_g\) and \(B_g\) are set to \(I_g\).

void	resetStartSubstream ()
	Reinitializes the stream to the beginning of its current substream: \(C_g\) is set to \(B_g\).

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 \(N_g\).

double	nextDouble ()
	Returns a (pseudo)random number from the uniform distribution over the interval \((0,1)\), using this stream, after advancing its state by one step. More...

void	nextArrayOfDouble (double[] u, int start, int n)
	Generates `n` (pseudo)random numbers from the uniform distribution and stores them into the array `u` starting at index `start`. More...

int	nextInt (int i, int j)
	Returns a (pseudo)random number from the discrete uniform distribution over the integers \(\{i,i+1,…,j\}\), using this stream. More...

void	nextArrayOfInt (int i, int j, int[] u, int start, int n)
	Generates `n` (pseudo)random numbers from the discrete uniform distribution over the integers \(\{i,i+1,…,j\}\), using this stream and stores the result in the array `u` starting at index `start`. More...

Public Member Functions inherited from RandomStream
String	toString ()
	Returns a string containing the current state of this stream. More...

Detailed Description

This class represents a random stream whose uniforms are cached for more efficiency when using common random numbers.

An object from this class is constructed with a reference to a RandomStream instance used to get the random numbers. These numbers are stored in an internal array to be retrieved later. The dimension of the array increases as the values are generated. If the nextDouble method is called after the object is reset, it gives back the cached values instead of computing new ones. If the cache is exhausted before the stream is reset, new values are computed, and added to the cache.

Such caching allows for a better performance with common random numbers, when generating uniforms is time-consuming. It can also help with restoring the simulation to a certain state without setting stream-specific seeds. However, using such caching may lead to memory problems if a large quantity of random numbers are needed.

Constructor & Destructor Documentation

◆ RandomStreamWithCache() [1/2]

RandomStreamWithCache ( RandomStream stream )

Constructs a new cached random stream with internal stream stream.

Parameters

stream the random stream whose uniforms are cached.

Exceptions

NullPointerException if stream is null.

◆ RandomStreamWithCache() [2/2]

RandomStreamWithCache	(	RandomStream	stream,
		int	initialCapacity
	)

Constructs a new cached random stream with internal stream stream.

The initialCapacity parameter is used to set the initial capacity of the internal array which can grow as needed; it does not limit the total size of the cache.

Parameters

stream	the random stream whose values are cached.
initialCapacity	the initial capacity of the cache.

Exceptions

NullPointerException if stream is null.

Member Function Documentation

◆ clearCache()

void clearCache ( )

Clears the cached values for this random stream.

Any subsequent call will then obtain new values from the internal stream.

◆ getCachedStream()

RandomStream getCachedStream ( )

Returns a reference to the random stream whose values are cached.

Returns: a reference to the random stream whose values are cached.

◆ getCachedValues()

DoubleArrayList getCachedValues ( )

Returns an array list containing the values cached by this random stream.

Returns: the array of cached values.

◆ getCacheIndex()

int getCacheIndex ( )

Return the index of the next cached value that will be returned by the stream.

If the cache is exhausted, the returned value corresponds to the value returned by getNumCachedValues, and a subsequent call to nextDouble will generate a new variate rather than reading a previous one from the cache. If caching is disabled, this always returns 0.

Returns: the index of the next cached value.

◆ getNumCachedValues()

int getNumCachedValues ( )

Returns the total number of values cached by this random stream.

Returns: the total number of cached values.

◆ initCache()

void initCache ( )

Resets this random stream to recover values from the cache.

Subsequent calls to nextDouble will return the cached uniforms until all the values are returned. When the array of cached values is exhausted, the internal random stream is used to generate new values which are added to the internal array as well. This method is equivalent to calling setCacheIndex(int).

◆ isCaching()

boolean isCaching ( )

Determines if the random stream is caching values, default being true.

When caching is turned OFF, the nextDouble method simply calls the corresponding method on the internal random stream, without storing the generated uniforms.

Returns: the caching indicator.

◆ nextArrayOfDouble()

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

Generates n (pseudo)random numbers from the uniform distribution and stores them into the array u starting at index start.

Parameters

u	array that will contain the generated uniforms
start	starting index, in the array `u`, to write uniforms from
n	number of uniforms to generate

Implements RandomStream.

◆ nextArrayOfInt()

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

Generates n (pseudo)random numbers from the discrete uniform distribution over the integers \(\{i,i+1,…,j\}\), using this stream and stores the result in the array u starting at index start.

(Calls nextInt n times.)

Parameters

i	smallest integer that can be generated
j	greatest integer that can be generated
u	array that will contain the generated values
start	starting index, in the array `u`, to write integers from
n	number of values being generated

Implements RandomStream.

◆ nextDouble()

double nextDouble ( )

Returns a (pseudo)random number from the uniform distribution over the interval \((0,1)\), using this stream, after advancing its state by one step.

The generators programmed in SSJ never return the values 0 or 1.

Returns: the next generated uniform

Implements RandomStream.

◆ nextInt()

int nextInt	(	int	i,
		int	j
	)

Returns a (pseudo)random number from the discrete uniform distribution over the integers \(\{i,i+1,…,j\}\), using this stream.

(Calls nextDouble once.)

Parameters

i	smallest integer that can be generated
j	greatest integer that can be generated

Returns: the generated integer

Implements RandomStream.

◆ setCachedStream()

void setCachedStream ( RandomStream stream )

Sets the random stream whose values are cached to stream.

If the stream is changed, the clearCache method is called to clear the cache.

Parameters

stream the new random stream whose values will be cached.

Exceptions

NullPointerException if stream is null.

◆ setCachedValues()

void setCachedValues ( DoubleArrayList values )

Sets the array list containing the cached values to values.

This resets the cache index to the size of the given array.

Parameters

values the array list of cached values.

Exceptions

NullPointerException if values is null.

◆ setCacheIndex()

void setCacheIndex ( int newIndex )

Sets the index, in the cache, of the next value returned by nextDouble.

If newIndex is 0, this is equivalent to calling initCache. If newIndex is getNumCachedValues, subsequent calls to nextDouble will add new values to the cache.

Parameters

newIndex the new index.

Exceptions

IllegalArgumentException if newIndex is negative or greater than or equal to the cache size.

◆ setCaching()

void setCaching ( boolean caching )

Sets the caching indicator to caching.

If caching is turned OFF, this method calls clearCache to clear the cached values.

Parameters

caching the new value of the caching indicator.

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

RandomStreamWithCache.java

Public Member Functions

Detailed Description

Constructor & Destructor Documentation

◆ RandomStreamWithCache() [1/2]

◆ RandomStreamWithCache() [2/2]

Member Function Documentation

◆ clearCache()

◆ getCachedStream()

◆ getCachedValues()

◆ getCacheIndex()

◆ getNumCachedValues()

◆ initCache()

◆ isCaching()

◆ nextArrayOfDouble()

◆ nextArrayOfInt()

◆ nextDouble()

◆ nextInt()

◆ setCachedStream()

◆ setCachedValues()

◆ setCacheIndex()

◆ setCaching()