org.apache.commons.math3.random
Class ISAACRandom

java.lang.Object
  extended by org.apache.commons.math3.random.BitsStreamGenerator
      extended by org.apache.commons.math3.random.ISAACRandom
All Implemented Interfaces:
java.io.Serializable, RandomGenerator

public class ISAACRandom
extends BitsStreamGenerator
implements java.io.Serializable

ISAAC: a fast cryptographic pseudo-random number generator
ISAAC (Indirection, Shift, Accumulate, Add, and Count) generates 32-bit random numbers. ISAAC has been designed to be cryptographically secure and is inspired by RC4. Cycles are guaranteed to be at least 240 values long, and they are 28295 values long on average. The results are uniformly distributed, unbiased, and unpredictable unless you know the seed.
This code is based (with minor changes and improvements) on the original implementation of the algorithm by Bob Jenkins.

Since:
3.0
Version:
$Id: ISAACRandom.java 1416643 2012-12-03 19:37:14Z tn $
See Also:
Serialized Form

Field Summary
private  int[] arr
          Service variable.
private  int count
          Count through the results in rsl[]
private static int GLD_RATIO
          The golden ratio
private static int H_SIZE
          Half-size of rsl[] and mem[]
private  int isaacA
          Accumulator
private  int isaacB
          The last result
private  int isaacC
          Counter, guarantees cycle is at least 2^40
private  int isaacI
          Service variable.
private  int isaacJ
          Service variable.
private  int isaacX
          Service variable.
private static int MASK
          For pseudo-random lookup
private  int[] mem
          The internal state
private  int[] rsl
          The results given to the user
private static long serialVersionUID
          Serializable version identifier
private static int SIZE
          Size of rsl[] and mem[]
private static int SIZE_L
          Log of size of rsl[] and mem[]
 
Constructor Summary
ISAACRandom()
          Creates a new ISAAC random number generator.
ISAACRandom(int[] seed)
          Creates a new ISAAC random number generator using an int array seed.
ISAACRandom(long seed)
          Creates a new ISAAC random number generator using a single long seed.
 
Method Summary
private  void initState()
          Initialize, or reinitialize, this instance of rand.
private  void isaac()
          Generate 256 results
private  void isaac2()
          Intermediate internal loop.
private  void isaac3()
          Lowest level internal loop.
protected  int next(int bits)
          Generate next pseudorandom number.
 void setSeed(int seed)
          Sets the seed of the underlying random number generator using an int seed.
 void setSeed(int[] seed)
          Sets the seed of the underlying random number generator using an int array seed.
 void setSeed(long seed)
          Sets the seed of the underlying random number generator using a long seed.
private  void setState(int start)
          Set the state by copying the internal arrays.
private  void shuffle()
          Shuffle array.
 
Methods inherited from class org.apache.commons.math3.random.BitsStreamGenerator
clear, nextBoolean, nextBytes, nextDouble, nextFloat, nextGaussian, nextInt, nextInt, nextLong
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

serialVersionUID

private static final long serialVersionUID
Serializable version identifier

See Also:
Constant Field Values

SIZE_L

private static final int SIZE_L
Log of size of rsl[] and mem[]

See Also:
Constant Field Values

SIZE

private static final int SIZE
Size of rsl[] and mem[]

See Also:
Constant Field Values

H_SIZE

private static final int H_SIZE
Half-size of rsl[] and mem[]

See Also:
Constant Field Values

MASK

private static final int MASK
For pseudo-random lookup

See Also:
Constant Field Values

GLD_RATIO

private static final int GLD_RATIO
The golden ratio

See Also:
Constant Field Values

rsl

private final int[] rsl
The results given to the user


mem

private final int[] mem
The internal state


count

private int count
Count through the results in rsl[]


isaacA

private int isaacA
Accumulator


isaacB

private int isaacB
The last result


isaacC

private int isaacC
Counter, guarantees cycle is at least 2^40


arr

private final int[] arr
Service variable.


isaacX

private int isaacX
Service variable.


isaacI

private int isaacI
Service variable.


isaacJ

private int isaacJ
Service variable.

Constructor Detail

ISAACRandom

public ISAACRandom()
Creates a new ISAAC random number generator.
The instance is initialized using a combination of the current time and system hash code of the instance as the seed.


ISAACRandom

public ISAACRandom(long seed)
Creates a new ISAAC random number generator using a single long seed.

Parameters:
seed - Initial seed.

ISAACRandom

public ISAACRandom(int[] seed)
Creates a new ISAAC random number generator using an int array seed.

Parameters:
seed - Initial seed. If null, the seed will be related to the current time.
Method Detail

setSeed

public void setSeed(int seed)
Sets the seed of the underlying random number generator using an int seed.

Sequences of values generated starting with the same seeds should be identical.

Specified by:
setSeed in interface RandomGenerator
Specified by:
setSeed in class BitsStreamGenerator
Parameters:
seed - the seed value

setSeed

public void setSeed(long seed)
Sets the seed of the underlying random number generator using a long seed.

Sequences of values generated starting with the same seeds should be identical.

Specified by:
setSeed in interface RandomGenerator
Specified by:
setSeed in class BitsStreamGenerator
Parameters:
seed - the seed value

setSeed

public void setSeed(int[] seed)
Sets the seed of the underlying random number generator using an int array seed.

Sequences of values generated starting with the same seeds should be identical.

Specified by:
setSeed in interface RandomGenerator
Specified by:
setSeed in class BitsStreamGenerator
Parameters:
seed - the seed value

next

protected int next(int bits)
Generate next pseudorandom number.

This method is the core generation algorithm. It is used by all the public generation methods for the various primitive types BitsStreamGenerator.nextBoolean(), BitsStreamGenerator.nextBytes(byte[]), BitsStreamGenerator.nextDouble(), BitsStreamGenerator.nextFloat(), BitsStreamGenerator.nextGaussian(), BitsStreamGenerator.nextInt(), BitsStreamGenerator.next(int) and BitsStreamGenerator.nextLong().

Specified by:
next in class BitsStreamGenerator
Parameters:
bits - number of random bits to produce
Returns:
random bits generated

isaac

private void isaac()
Generate 256 results


isaac2

private void isaac2()
Intermediate internal loop.


isaac3

private void isaac3()
Lowest level internal loop.


initState

private void initState()
Initialize, or reinitialize, this instance of rand.


shuffle

private void shuffle()
Shuffle array.


setState

private void setState(int start)
Set the state by copying the internal arrays.

Parameters:
start - First index into mem array.


Copyright (c) 2003-2013 Apache Software Foundation