Class MersenneTwister
- All Implemented Interfaces:
RandomIntSource
,RestorableUniformRandomProvider
,UniformRandomProvider
This generator features an extremely long period (219937-1) and 623-dimensional equidistribution up to 32 bits accuracy. The home page for this generator is located at http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html.
This generator is described in a paper by Makoto Matsumoto and Takuji Nishimura in 1998: 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
This class is mainly a Java port of the 2002-01-26 version of the generator written in C by Makoto Matsumoto and Takuji Nishimura. Here is their original copyright:
Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura, All rights reserved. |
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions
are met:
|
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
- Since:
- 1.0
- See Also:
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Field Summary
FieldsModifier and TypeFieldDescriptionprivate static final long
Mask 32 most significant bits.private static final int
Least significant r bits.private static final long
Least significant r bits.private static final int
Period second parameter.private static final int[]
X * MATRIX_A for X = {0, 1}.private final int[]
Bytes pool.private int
Current index in the bytes pool.private static final int
Size of the bytes pool.private static final int
Most significant w-r bits.private static final long
Most significant w-r bits. -
Constructor Summary
Constructors -
Method Summary
Modifier and TypeMethodDescriptionprivate static void
fillStateMersenneTwister
(int[] state, int[] inputSeed) Utility for wholly filling astate
array with non-zero bytes, even if theseed
has a smaller size.protected byte[]
Creates a snapshot of the RNG state.private static void
initializeState
(int[] state) Fill the state using a defined pseudo-random sequence.private static int
mixSeedAndState
(int[] state, int[] seed) Mix the seed into the state using a non-linear combination.private static void
mixState
(int[] state, int startIndex) Mix each position of the state using a non-linear combination.int
next()
Return the next random value.private void
setSeedInternal
(int[] seed) Initializes the generator with the given seed.protected void
setStateInternal
(byte[] s) Resets the RNG to the givenstate
.Methods inherited from class org.apache.commons.rng.core.source32.IntProvider
nextBoolean, nextBytes, nextBytes, nextBytesFill, nextDouble, nextInt, nextLong, resetCachedState
Methods inherited from class org.apache.commons.rng.core.BaseProvider
checkIndex, checkStateSize, composeStateInternal, extendSeed, extendSeed, fillState, fillState, restoreState, saveState, splitStateInternal, toString
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Field Details
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INT_MASK_LONG
private static final long INT_MASK_LONGMask 32 most significant bits.- See Also:
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UPPER_MASK_LONG
private static final long UPPER_MASK_LONGMost significant w-r bits.- See Also:
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LOWER_MASK_LONG
private static final long LOWER_MASK_LONGLeast significant r bits.- See Also:
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UPPER_MASK
private static final int UPPER_MASKMost significant w-r bits.- See Also:
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LOWER_MASK
private static final int LOWER_MASKLeast significant r bits.- See Also:
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N
private static final int NSize of the bytes pool.- See Also:
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M
private static final int MPeriod second parameter.- See Also:
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MAG01
private static final int[] MAG01X * MATRIX_A for X = {0, 1}. -
mt
private final int[] mtBytes pool. -
mti
private int mtiCurrent index in the bytes pool.
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Constructor Details
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MersenneTwister
public MersenneTwister(int[] seed) Creates a new random number generator.- Parameters:
seed
- Initial seed.
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Method Details
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getStateInternal
protected byte[] getStateInternal()Creates a snapshot of the RNG state.- Overrides:
getStateInternal
in classIntProvider
- Returns:
- the internal state.
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setStateInternal
protected void setStateInternal(byte[] s) Resets the RNG to the givenstate
.- Overrides:
setStateInternal
in classIntProvider
- Parameters:
s
- State (previously obtained by a call toBaseProvider.getStateInternal()
).- See Also:
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setSeedInternal
private void setSeedInternal(int[] seed) Initializes the generator with the given seed.- Parameters:
seed
- Initial seed.
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fillStateMersenneTwister
private static void fillStateMersenneTwister(int[] state, int[] inputSeed) Utility for wholly filling astate
array with non-zero bytes, even if theseed
has a smaller size. The procedure is the one defined by the standard implementation of the algorithm.- Parameters:
state
- State to be filled (must be allocated).inputSeed
- Seed (cannot benull
).
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initializeState
private static void initializeState(int[] state) Fill the state using a defined pseudo-random sequence.- Parameters:
state
- State to be filled (must be allocated).
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mixSeedAndState
private static int mixSeedAndState(int[] state, int[] seed) Mix the seed into the state using a non-linear combination. The procedure usesk
steps wherek = max(state.length, seed.length)
. If the seed is smaller than the state it is wrapped to obtain enough values. If the seed is larger than the state then the procedure visits entries in the state multiple times.Returns the index immediately after the most recently visited position in the state array.
- Parameters:
state
- State to be filled (must be allocated).seed
- Seed (must be at least length 1).- Returns:
- the next index
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mixState
private static void mixState(int[] state, int startIndex) Mix each position of the state using a non-linear combination. The procedure starts from the specified index in the state array and wraps iteration through the array if required.- Parameters:
state
- State to be filled (must be allocated).startIndex
- The index to begin within the state array.
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next
public int next()Return the next random value.- Returns:
- the next random value.
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