SSJ
3.3.1
Stochastic Simulation in Java

This class represents a random stream whose uniforms are cached for more efficiency when using common random numbers. More...
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...  
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 timeconsuming. It can also help with restoring the simulation to a certain state without setting streamspecific seeds. However, using such caching may lead to memory problems if a large quantity of random numbers are needed.
RandomStreamWithCache  (  RandomStream  stream  ) 
Constructs a new cached random stream with internal stream stream
.
stream  the random stream whose uniforms are cached. 
NullPointerException  if stream is null . 
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.
stream  the random stream whose values are cached. 
initialCapacity  the initial capacity of the cache. 
NullPointerException  if stream is null . 
void clearCache  (  ) 
Clears the cached values for this random stream.
Any subsequent call will then obtain new values from the internal stream.
RandomStream getCachedStream  (  ) 
Returns a reference to the random stream whose values are cached.
DoubleArrayList getCachedValues  (  ) 
Returns an array list containing the values cached by this random stream.
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.
int getNumCachedValues  (  ) 
Returns the total number of values cached by this random stream.
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).
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.
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
.
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.
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.)
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.
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.
Implements RandomStream.
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.)
i  smallest integer that can be generated 
j  greatest integer that can be generated 
Implements RandomStream.
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.
stream  the new random stream whose values will be cached. 
NullPointerException  if stream is null . 
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.
values  the array list of cached values. 
NullPointerException  if values is null . 
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.
newIndex  the new index. 
IllegalArgumentException  if newIndex is negative or greater than or equal to the cache size. 
void setCaching  (  boolean  caching  ) 
Sets the caching indicator to caching
.
If caching is turned OFF, this method calls clearCache to clear the cached values.
caching  the new value of the caching indicator. 