Package org.apache.commons.rng.core.source64

Class Philox4x64

java.lang.Object

org.apache.commons.rng.core.BaseProvider

org.apache.commons.rng.core.source64.LongProvider

org.apache.commons.rng.core.source64.Philox4x64

All Implemented Interfaces:

ArbitrarilyJumpableUniformRandomProvider, RandomLongSource, JumpableUniformRandomProvider, LongJumpableUniformRandomProvider, RestorableUniformRandomProvider, UniformRandomProvider

public final class Philox4x64
extends LongProvider
implements LongJumpableUniformRandomProvider, ArbitrarilyJumpableUniformRandomProvider

This class implements the Philox4x64 256-bit counter-based generator with 10 rounds.

This is a member of the Philox family of generators. Memory footprint is 384 bits and the period is 2²⁵⁸.

Jumping in the sequence is essentially instantaneous. This generator provides both subsequences and arbitrary jumps for easy parallelization.

References:

1. Salmon, J.K. et al (2011) Parallel Random Numbers: As Easy as 1,2,3.

Since:

1.7

Constructor Summary

Constructors

Constructor	Description
Philox4x64(long[] seed)	Creates a new instance given 6 long numbers containing, key (first two longs) and the counter (next 4 longs, low bits = first long).

Method Summary

Modifier and Type	Method	Description
protected byte[]	getStateInternal()	Creates a snapshot of the RNG state.
UniformRandomProvider	jump()
ArbitrarilyJumpableUniformRandomProvider	jump(double distance)
ArbitrarilyJumpableUniformRandomProvider	jumpPowerOfTwo(int logDistance)
Stream<ArbitrarilyJumpableUniformRandomProvider>	jumps(double distance)
JumpableUniformRandomProvider	longJump()
long	next()	Return the next random value.
protected void	setStateInternal(byte[] s)	Resets the RNG to the given state.

Methods inherited from class org.apache.commons.rng.core.source64.LongProvider

nextBoolean, nextInt, nextLong, resetCachedState

Methods inherited from class org.apache.commons.rng.core.BaseProvider

checkIndex, checkStateSize, composeStateInternal, extendSeed, extendSeed, fillState, fillState, restoreState, saveState, splitStateInternal, toString

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface org.apache.commons.rng.ArbitrarilyJumpableUniformRandomProvider

jumps

Methods inherited from interface org.apache.commons.rng.JumpableUniformRandomProvider

jumps, jumps

Methods inherited from interface org.apache.commons.rng.LongJumpableUniformRandomProvider

longJumps, longJumps

Methods inherited from interface org.apache.commons.rng.UniformRandomProvider

doubles, doubles, doubles, doubles, ints, ints, ints, ints, longs, longs, longs, longs, nextBoolean, nextBytes, nextBytes, nextDouble, nextDouble, nextDouble, nextFloat, nextFloat, nextFloat, nextInt, nextInt, nextInt, nextLong, nextLong, nextLong

Constructor Detail

Philox4x64

public Philox4x64(long[] seed)

Creates a new instance given 6 long numbers containing, key (first two longs) and the counter (next 4 longs, low bits = first long). The counter is not scrambled and may be used to create contiguous blocks with size a multiple of 4 longs. For example, setting seed[2] = 1 is equivalent to start with seed[2]=0 and calling next() 4 times.

Parameters:

seed - Array of size 6 defining key0,key1,counter0,counter1,counter2,counter3. If the size is smaller, zero values are assumed.

Method Detail

getStateInternal

protected byte[] getStateInternal()

Creates a snapshot of the RNG state.

Overrides:

getStateInternal in class LongProvider

Returns:

the internal state.

setStateInternal

protected void setStateInternal(byte[] s)

Resets the RNG to the given state.

Overrides:

setStateInternal in class LongProvider

Parameters:

s - State (previously obtained by a call to BaseProvider.getStateInternal()).

See Also:

BaseProvider.checkStateSize(byte[],int)

next

public long next()

Return the next random value.

Specified by:

next in interface RandomLongSource

Returns:

the next random value.

jump

public UniformRandomProvider jump()

The jump size is the equivalent of 2¹³⁰ calls to nextLong(). It can provide up to 2¹²⁸ non-overlapping subsequences.

Specified by:

jump in interface JumpableUniformRandomProvider

longJump

public JumpableUniformRandomProvider longJump()

The jump size is the equivalent of 2¹⁹⁴ calls to nextLong(). It can provide up to 2⁶⁴ non-overlapping subsequences of length 2¹⁹⁴; each subsequence can provide up to 2⁶⁴ non-overlapping subsequences of length 2¹³⁰ using the jump() method.

Specified by:

longJump in interface LongJumpableUniformRandomProvider

jump

public ArbitrarilyJumpableUniformRandomProvider jump(double distance)

Specified by:

jump in interface ArbitrarilyJumpableUniformRandomProvider

jumpPowerOfTwo

public ArbitrarilyJumpableUniformRandomProvider jumpPowerOfTwo(int logDistance)

Specified by:

jumpPowerOfTwo in interface ArbitrarilyJumpableUniformRandomProvider

jumps

public Stream<ArbitrarilyJumpableUniformRandomProvider> jumps(double distance)

Specified by:

jumps in interface ArbitrarilyJumpableUniformRandomProvider