Class XoShiRo256PlusRandom
 All Implemented Interfaces:
Serializable
public class XoShiRo256PlusRandom extends Random
XoShiRo256StarStarRandom
. 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 XoShiRo256StarStarRandom
. If you are tight on space,
you might try XoRoShiRo128PlusRandom
.
By using the supplied jump()
method it is possible to generate nonoverlapping long sequences
for parallel computations; longJump()
makes it possible to create several
starting points, each providing several nonoverlapping sequences, for distributed computations. This class provides also a split()
method to support recursive parallel computations, in the spirit of
SplittableRandom
.
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 to split()
is
now different, and the result of split()
is initialized in a different way.
Note that this is not a secure generator.
 Version:
 1.0
 See Also:
it.unimi.dsi.util
,RandomGenerator
,XoShiRo256PlusRandomGenerator
, Serialized Form

Constructor Summary
Constructors Modifier Constructor Description XoShiRo256PlusRandom()
Creates a new generator seeded usingUtil.randomSeed()
.XoShiRo256PlusRandom(long seed)
Creates a new generator using a given seed.protected
XoShiRo256PlusRandom(long s0, long s1, long s2, long s3)

Method Summary
Modifier and Type Method Description XoShiRo256PlusRandom
copy()
Returns a copy of this generator.XoShiRo256PlusRandom
jump()
The jump function for this generator.protected XoShiRo256PlusRandom
jump(long[] jump)
XoShiRo256PlusRandom
longJump()
The longjump function for this generator.static void
main(String[] arg)
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 multiplicationfree 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.XoShiRo256PlusRandom
split()
Returns a new instance that shares no mutable state with this instance.

Constructor Details

XoShiRo256PlusRandom
protected XoShiRo256PlusRandom(long s0, long s1, long s2, long s3) 
XoShiRo256PlusRandom
public XoShiRo256PlusRandom()Creates a new generator seeded usingUtil.randomSeed()
. 
XoShiRo256PlusRandom
public XoShiRo256PlusRandom(long seed)Creates a new generator using a given seed. Parameters:
seed
 a seed for the generator.


Method Details

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 nonoverlapping sequences. Returns:
 a copy of this generator.

nextLong
public long nextLong() 
nextInt
public int nextInt() 
nextInt
public int nextInt(int n) 
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 64bit 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).

nextDouble
public double nextDouble() Overrides:
nextDouble
in classRandom

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 multiplicationfree 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.

nextFloat
public float nextFloat() 
nextBoolean
public boolean nextBoolean() Overrides:
nextBoolean
in classRandom

nextBytes
public void nextBytes(byte[] bytes) 
jump

jump
The jump function for this generator. It is equivalent to 2^{128} calls tonextLong()
; it can be used to generate 2^{128} nonoverlapping subsequences for parallel computations. Returns:
 this generator.
 See Also:
copy()

longJump
The longjump function for this generator. It is equivalent to 2^{192} calls tonextLong()
; it can be used to generate 2^{64} starting points, from each of whichjump()
will generate 2^{64} nonoverlapping subsequences for parallel distributed computations. Returns:
 this generator.
 See Also:
copy()

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.

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. 
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.

main
