Class MersenneTwisterFast
- java.lang.Object
-
- pal.math.MersenneTwisterFast
-
- All Implemented Interfaces:
java.io.Serializable
public class MersenneTwisterFast extends java.lang.Object implements java.io.Serializable
MersenneTwisterFast: A simulation quality fast random number generator (MT19937) with the same public methods as java.util.Random.About the Mersenne Twister. This is a Java version of the C-program for MT19937: Integer version. next(32) generates one pseudorandom unsigned integer (32bit) which is uniformly distributed among 0 to 2^32-1 for each call. next(int bits) >>>'s by (32-bits) to get a value ranging between 0 and 2^bits-1 long inclusive; hope that's correct. setSeed(seed) set initial values to the working area of 624 words. For setSeed(seed), seed is any 32-bit integer except for 0.
Reference. M. Matsumoto and T. Nishimura, "Mersenne Twister: A 623-Dimensionally Equidistributed Uniform Pseudo-Random Number Generator", ACM Transactions on Modeling and Computer Simulation, Vol. 8, No. 1, January 1998, pp 3--30.
Bug Fixes. This implementation implements the bug fixes made in Java 1.2's version of Random, which means it can be used with earlier versions of Java. See the JDK 1.2 java.util.Random documentation for further documentation on the random-number generation contracts made. Additionally, there's an undocumented bug in the JDK java.util.Random.nextBytes() method, which this code fixes.
Important Note. Just like java.util.Random, this generator accepts a long seed but doesn't use all of it. java.util.Random uses 48 bits. The Mersenne Twister instead uses 32 bits (int size). So it's best if your seed does not exceed the int range.
- added shuffling method (Alexei Drummond)
- See Also:
- Serialized Form
-
-
Constructor Summary
Constructors Constructor Description MersenneTwisterFast()
Constructor using the time of day as default seed.MersenneTwisterFast(long seed)
Constructor using a given seed.
-
Method Summary
All Methods Static Methods Instance Methods Concrete Methods Modifier and Type Method Description static boolean
getNextBoolean()
Access a default instance of this class, access is synchronizedstatic byte
getNextByte()
Access a default instance of this class, access is synchronizedstatic void
getNextBytes(byte[] bs)
Access a default instance of this class, access is synchronizedstatic char
getNextChar()
Access a default instance of this class, access is synchronizedstatic double
getNextDouble()
Access a default instance of this class, access is synchronizedstatic float
getNextFloat()
Access a default instance of this class, access is synchronizedstatic int
getNextInt()
Access a default instance of this class, access is synchronizedstatic long
getNextLong()
Access a default instance of this class, access is synchronizedstatic short
getNextShort()
Access a default instance of this class, access is synchronizedboolean
nextBoolean()
byte
nextByte()
void
nextBytes(byte[] bytes)
char
nextChar()
double
nextDouble()
float
nextFloat()
double
nextGaussian()
int
nextInt()
int
nextInt(int n)
Returns an integer drawn uniformly from 0 to n-1.long
nextLong()
short
nextShort()
void
setSeed(long seed)
Initalize the pseudo random number generator.void
shuffle(int[] array)
Shuffles an array.void
shuffle(int[] array, int numberOfShuffles)
Shuffles an array by repeatedly choosing two random members and swapping them.void
shuffle(java.lang.Object[] array)
Shuffles an array of objects.int[]
shuffled(int l)
Generates an array of ints that are shuffledvoid
shuffleSubset(int startIndex, int length, java.lang.Object[] array)
Shuffles an array of objects.
-
-
-
Constructor Detail
-
MersenneTwisterFast
public MersenneTwisterFast()
Constructor using the time of day as default seed.
-
MersenneTwisterFast
public MersenneTwisterFast(long seed)
Constructor using a given seed. Though you pass this seed in as a long, it's best to make sure it's actually an integer.- Parameters:
seed
- generator starting number, often the time of day.
-
-
Method Detail
-
shuffle
public final void shuffle(int[] array)
Shuffles an array.- Parameters:
array
- The array of ints to shuffle
-
shuffleSubset
public final void shuffleSubset(int startIndex, int length, java.lang.Object[] array)
Shuffles an array of objects.- Parameters:
array
- The array of objects to shufflestartIndex
- the starting index of the portion of the array to shufflelength
- the length of the portion of the array to shuffle
-
shuffle
public final void shuffle(java.lang.Object[] array)
Shuffles an array of objects.- Parameters:
array
- The array of objects to shuffle
-
shuffle
public final void shuffle(int[] array, int numberOfShuffles)
Shuffles an array by repeatedly choosing two random members and swapping them.- Parameters:
numberOfShuffles
- The number of times to do the random swap operationarray
- The array of ints to shuffle
-
shuffled
public int[] shuffled(int l)
Generates an array of ints that are shuffled- Parameters:
l
- length of the array required.- Returns:
- an array of shuffled indices of the specified length.
-
setSeed
public final void setSeed(long seed)
Initalize the pseudo random number generator. The Mersenne Twister only uses an integer for its seed; It's best that you don't pass in a long that's bigger than an int.- Parameters:
seed
- from constructor
-
nextInt
public final int nextInt()
-
nextShort
public final short nextShort()
-
nextChar
public final char nextChar()
-
nextBoolean
public final boolean nextBoolean()
-
nextByte
public final byte nextByte()
-
nextBytes
public final void nextBytes(byte[] bytes)
-
nextLong
public final long nextLong()
-
nextDouble
public final double nextDouble()
-
nextGaussian
public final double nextGaussian()
-
nextFloat
public final float nextFloat()
-
nextInt
public int nextInt(int n)
Returns an integer drawn uniformly from 0 to n-1. Suffice it to say, n must be > 0, or an IllegalArgumentException is raised.
-
getNextByte
public static final byte getNextByte()
Access a default instance of this class, access is synchronized
-
getNextBoolean
public static final boolean getNextBoolean()
Access a default instance of this class, access is synchronized
-
getNextBytes
public static final void getNextBytes(byte[] bs)
Access a default instance of this class, access is synchronized
-
getNextChar
public static final char getNextChar()
Access a default instance of this class, access is synchronized
-
getNextDouble
public static final double getNextDouble()
Access a default instance of this class, access is synchronized
-
getNextFloat
public static final float getNextFloat()
Access a default instance of this class, access is synchronized
-
getNextLong
public static final long getNextLong()
Access a default instance of this class, access is synchronized
-
getNextShort
public static final short getNextShort()
Access a default instance of this class, access is synchronized
-
getNextInt
public static final int getNextInt()
Access a default instance of this class, access is synchronized
-
-