Class XoRoShiRo128PlusPlusRandom
 java.lang.Object

 java.util.Random

 it.unimi.dsi.util.XoRoShiRo128PlusPlusRandom

 All Implemented Interfaces:
Serializable
public class XoRoShiRo128PlusPlusRandom extends Random
A fast, allpurpose, rocksolid, smallstate pseudorandom number generator. It has excellent speed, but its state space (128 bits) that is large enough for mild parallelism only; it passes all tests we are aware of. In Java, it is slightly faster than aXoRoShiRo128StarStarRandom
. More information can be found at our PRNG page.If you need to generate just floatingpoint numbers,
XoRoShiRo128PlusRandom
is slightly faster. If you can use more space, you might tryXoShiRo256PlusPlusRandom
.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 asplit()
method to support recursive parallel computations, in the spirit ofSplittableRandom
.Note that this is not a secure generator.
 Version:
 1.0
 See Also:
it.unimi.dsi.util
,RandomGenerator
,XoRoShiRo128PlusPlusRandomGenerator
, Serialized Form


Constructor Summary
Constructors Modifier Constructor Description XoRoShiRo128PlusPlusRandom()
Creates a new generator seeded usingUtil.randomSeed()
.XoRoShiRo128PlusPlusRandom(long seed)
Creates a new generator using a given seed.protected
XoRoShiRo128PlusPlusRandom(long s0, long s1)

Method Summary
Modifier and Type Method Description XoRoShiRo128PlusPlusRandom
copy()
Returns a copy of this generator.XoRoShiRo128PlusPlusRandom
jump()
The jump function for this generator.XoRoShiRo128PlusPlusRandom
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.XoRoShiRo128PlusPlusRandom
split()
Returns a new instance that shares no mutable state with this instance.



Constructor Detail

XoRoShiRo128PlusPlusRandom
protected XoRoShiRo128PlusPlusRandom(long s0, long s1)

XoRoShiRo128PlusPlusRandom
public XoRoShiRo128PlusPlusRandom()
Creates a new generator seeded usingUtil.randomSeed()
.

XoRoShiRo128PlusPlusRandom
public XoRoShiRo128PlusPlusRandom(long seed)
Creates a new generator using a given seed. Parameters:
seed
 a seed for the generator.


Method Detail

copy
public XoRoShiRo128PlusPlusRandom 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()
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(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.  Since:
 2.4.1

nextBoolean
public boolean nextBoolean()
 Overrides:
nextBoolean
in classRandom

jump
public XoRoShiRo128PlusPlusRandom jump()
The jump function for this generator. It is equivalent to 2^{64} calls tonextLong()
; it can be used to generate 2^{64} nonoverlapping subsequences for parallel computations. Returns:
 this generator.
 See Also:
copy()

longJump
public XoRoShiRo128PlusPlusRandom longJump()
The longjump function for this generator. It is equivalent to 2^{96} calls tonextLong()
; it can be used to generate 2^{32} starting points, from each of whichjump()
will generate 2^{32} nonoverlapping subsequences for parallel distributed computations. Returns:
 this generator.
 See Also:
copy()

split
public XoRoShiRo128PlusPlusRandom 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. 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
public static void main(String[] arg)

