Class XorShift1024StarPhiRandom
 java.lang.Object

 java.util.Random

 it.unimi.dsi.util.XorShift1024StarPhiRandom

 All Implemented Interfaces:
Serializable
public class XorShift1024StarPhiRandom extends Random
A fast, highquality pseudorandom number generator that combines a longperiod instance of George Marsaglia's Xorshift generators (described in “Xorshift RNGs”, Journal of Statistical Software, 8:1−6, 2003) with a multiplication. More information can be found at our PRNG page.By using the supplied
jump()
method it is possible to generate nonoverlapping long sequences for parallel computations. This class provides also asplit()
method to support recursive parallel computations, in the spirit ofSplittableRandom
.Note that this is not a secure generator.


Constructor Summary
Constructors Constructor Description XorShift1024StarPhiRandom()
Creates a new generator seeded usingUtil.randomSeed()
.XorShift1024StarPhiRandom(long seed)
Creates a new generator using a given seed.

Method Summary
Modifier and Type Method Description void
jump()
The jump function for this generator.protected int
next(int bits)
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, int p)
Sets the state of this generator.XorShift1024StarPhiRandom
split()
Returns a new instance that shares no mutable state with this instance.



Constructor Detail

XorShift1024StarPhiRandom
public XorShift1024StarPhiRandom()
Creates a new generator seeded usingUtil.randomSeed()
.

XorShift1024StarPhiRandom
public XorShift1024StarPhiRandom(long seed)
Creates a new generator using a given seed. Parameters:
seed
 a seed for the generator.


Method Detail

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}.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.

nextBoolean
public boolean nextBoolean()
 Overrides:
nextBoolean
in classRandom

jump
public void jump()
The jump function for this generator. It is equivalent to 2^{512} calls tonextLong()
; it can be used to generate 2^{512} nonoverlapping subsequences for parallel computations.

split
public XorShift1024StarPhiRandom 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, int p)
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 16 longs; at least one must be nonzero.p
 the internal index.

