Class XoShiRo256PlusRandomGenerator
- java.lang.Object
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- org.apache.commons.math3.random.AbstractRandomGenerator
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- it.unimi.dsi.util.XoShiRo256PlusRandomGenerator
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- All Implemented Interfaces:
java.io.Serializable
,org.apache.commons.math3.random.RandomGenerator
public class XoShiRo256PlusRandomGenerator extends org.apache.commons.math3.random.AbstractRandomGenerator implements java.io.Serializable
A fast, rock-solid pseudorandom number generator for floating-point generation. It has excellent speed, a state space (256 bits) that is large enough for any parallel application, and it is faster thanXoShiRo256StarStarRandomGenerator
. It passes all tests we are aware of except for the lowest three bits, which might fail linearity tests (and just those), so if low linear complexity is not considered an issue (as it is usually the case) it can be used to generate integer outputs, too. More information can be found at our PRNG page.If you need a general PRNG, use
XoShiRo256StarStarRandomGenerator
. If you are tight on space, you might tryXoRoShiRo128PlusRandomGenerator
.By using the supplied
jump()
method it is possible to generate non-overlapping long sequences for parallel computations;longJump()
makes it possible to create several starting points, each providing several non-overlapping sequences, for distributed computations. This class provides also asplit()
method to support recursive parallel computations, in the spirit ofSplittableRandom
.Warning: before release 2.6.3, the
split()
method would not alter the state of the caller, and it would return instances initialized in the same way if called multiple times. This was a major mistake in the implementation and it has been fixed, but as a consequence the output of the caller after a call tosplit()
is now different, and the result ofsplit()
is initialized in a different way.Note that this is not a secure generator.
- Version:
- 1.0
- See Also:
it.unimi.dsi.util
,RandomGenerator
,XoShiRo256PlusRandom
, Serialized Form
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Constructor Summary
Constructors Modifier Constructor Description XoShiRo256PlusRandomGenerator()
Creates a new generator seeded usingUtil.randomSeed()
.XoShiRo256PlusRandomGenerator(long seed)
Creates a new generator using a given seed.protected
XoShiRo256PlusRandomGenerator(long s0, long s1, long s2, long s3)
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Method Summary
All Methods Instance Methods Concrete Methods Modifier and Type Method Description XoShiRo256PlusRandomGenerator
copy()
Returns a copy of this generator.XoShiRo256PlusRandomGenerator
jump()
The jump function for this generator.protected XoShiRo256PlusRandomGenerator
jump(long[] jump)
XoShiRo256PlusRandomGenerator
longJump()
The long-jump function for this generator.boolean
nextBoolean()
void
nextBytes(byte[] bytes)
double
nextDouble()
double
nextDoubleFast()
Returns the next pseudorandom, uniformly distributeddouble
value between0.0
and1.0
from this random number generator's sequence, using a fast multiplication-free method which, however, can provide only 52 significant bits.float
nextFloat()
int
nextInt()
int
nextInt(int n)
long
nextLong()
long
nextLong(long n)
Returns a pseudorandom uniformly distributedlong
value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence.void
setSeed(long seed)
Sets the seed of this generator.void
setState(long[] state)
Sets the state of this generator.XoShiRo256PlusRandomGenerator
split()
Returns a new instance that shares no mutable state with this instance.
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Constructor Detail
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XoShiRo256PlusRandomGenerator
protected XoShiRo256PlusRandomGenerator(long s0, long s1, long s2, long s3)
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XoShiRo256PlusRandomGenerator
public XoShiRo256PlusRandomGenerator()
Creates a new generator seeded usingUtil.randomSeed()
.
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XoShiRo256PlusRandomGenerator
public XoShiRo256PlusRandomGenerator(long seed)
Creates a new generator using a given seed.- Parameters:
seed
- a seed for the generator.
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Method Detail
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copy
public XoShiRo256PlusRandomGenerator copy()
Returns a copy of this generator. The sequences produced by this generator and by the returned generator will be identical.This method is particularly useful in conjunction with the
jump()
(orlongJump()
) method: by calling repeatedlyjump().copy()
over a generator it is possible to create several generators producing non-overlapping sequences.- Returns:
- a copy of this generator.
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nextLong
public long nextLong()
- Specified by:
nextLong
in interfaceorg.apache.commons.math3.random.RandomGenerator
- Overrides:
nextLong
in classorg.apache.commons.math3.random.AbstractRandomGenerator
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nextInt
public int nextInt()
- Specified by:
nextInt
in interfaceorg.apache.commons.math3.random.RandomGenerator
- Overrides:
nextInt
in classorg.apache.commons.math3.random.AbstractRandomGenerator
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nextInt
public int nextInt(int n)
- Specified by:
nextInt
in interfaceorg.apache.commons.math3.random.RandomGenerator
- Overrides:
nextInt
in classorg.apache.commons.math3.random.AbstractRandomGenerator
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nextLong
public long nextLong(long n)
Returns a pseudorandom uniformly distributedlong
value between 0 (inclusive) and the specified value (exclusive), drawn from this random number generator's sequence. The algorithm used to generate the value guarantees that the result is uniform, provided that the sequence of 64-bit values produced by this generator is.- Parameters:
n
- the positive bound on the random number to be returned.- Returns:
- the next pseudorandom
long
value between0
(inclusive) andn
(exclusive).
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nextDouble
public double nextDouble()
- Specified by:
nextDouble
in interfaceorg.apache.commons.math3.random.RandomGenerator
- Specified by:
nextDouble
in classorg.apache.commons.math3.random.AbstractRandomGenerator
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nextDoubleFast
public double nextDoubleFast()
Returns the next pseudorandom, uniformly distributeddouble
value between0.0
and1.0
from this random number generator's sequence, using a fast multiplication-free method which, however, can provide only 52 significant bits.This method is faster than
nextDouble()
, but it can return only dyadic rationals of the form k / 2−52, instead of the standard k / 2−53. Before version 2.4.1, this was actually the standard implementation ofnextDouble()
, so you can use this method if you need to reproduce exactly results obtained using previous versions.The only difference between the output of this method and that of
nextDouble()
is an additional least significant bit set in half of the returned values. For most applications, this difference is negligible.- Returns:
- the next pseudorandom, uniformly distributed
double
value between0.0
and1.0
from this random number generator's sequence, using 52 significant bits only.
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nextFloat
public float nextFloat()
- Specified by:
nextFloat
in interfaceorg.apache.commons.math3.random.RandomGenerator
- Overrides:
nextFloat
in classorg.apache.commons.math3.random.AbstractRandomGenerator
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nextBoolean
public boolean nextBoolean()
- Specified by:
nextBoolean
in interfaceorg.apache.commons.math3.random.RandomGenerator
- Overrides:
nextBoolean
in classorg.apache.commons.math3.random.AbstractRandomGenerator
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nextBytes
public void nextBytes(byte[] bytes)
- Specified by:
nextBytes
in interfaceorg.apache.commons.math3.random.RandomGenerator
- Overrides:
nextBytes
in classorg.apache.commons.math3.random.AbstractRandomGenerator
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jump
protected XoShiRo256PlusRandomGenerator jump(long[] jump)
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jump
public XoShiRo256PlusRandomGenerator jump()
The jump function for this generator. It is equivalent to 2128 calls tonextLong()
; it can be used to generate 2128 non-overlapping subsequences for parallel computations.- Returns:
- this generator.
- See Also:
copy()
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longJump
public XoShiRo256PlusRandomGenerator longJump()
The long-jump function for this generator. It is equivalent to 2192 calls tonextLong()
; it can be used to generate 264 starting points, from each of whichjump()
will generate 264 non-overlapping subsequences for parallel distributed computations.- Returns:
- this generator.
- See Also:
copy()
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split
public XoShiRo256PlusRandomGenerator split()
Returns a new instance that shares no mutable state with this instance. The sequence generated by the new instance depends deterministically from the state of this instance, but the probability that the sequence generated by this instance and by the new instance overlap is negligible.Warning: before release 2.6.3, this method would not alter the state of the caller, and it would return instances initialized in the same way if called multiple times. This was a major mistake in the implementation and it has been fixed, but as a consequence the output of this instance after a call to this method is now different, and the returned instance is initialized in a different way.
- Returns:
- the new instance.
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setSeed
public void setSeed(long seed)
Sets the seed of this generator.The argument will be used to seed a
SplitMix64RandomGenerator
, whose output will in turn be used to seed this generator. This approach makes “warmup” unnecessary, and makes the probability of starting from a state with a large fraction of bits set to zero astronomically small.- Specified by:
setSeed
in interfaceorg.apache.commons.math3.random.RandomGenerator
- Specified by:
setSeed
in classorg.apache.commons.math3.random.AbstractRandomGenerator
- Parameters:
seed
- a seed for this generator.
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setState
public void setState(long[] state)
Sets the state of this generator.The internal state of the generator will be reset, and the state array filled with the provided array.
- Parameters:
state
- an array of 2 longs; at least one must be nonzero.
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