SFC64 Small Fast Chaotic PRNG¶

class
numpy.random.
SFC64
(seed=None)¶ BitGenerator for Chris DotyHumphrey’s Small Fast Chaotic PRNG.
Parameters:  seed : {None, int, array_like[ints], ISeedSequence}, optional
A seed to initialize the BitGenerator. If None, then fresh, unpredictable entropy will be pulled from the OS. If an
int
orarray_like[ints]
is passed, then it will be passed toSeedSequence
to derive the initial BitGenerator state. One may also pass in an implementor of the ISeedSequence interface likeSeedSequence
.
Notes
SFC64
is a 256bit implementation of Chris DotyHumphrey’s Small Fast Chaotic PRNG ([1]).SFC64
has a few different cycles that one might be on, depending on the seed; the expected period will be about ([2]).SFC64
incorporates a 64bit counter which means that the absolute minimum cycle length is and that distinct seeds will not run into each other for at least iterations.SFC64
provides a capsule containing function pointers that produce doubles, and unsigned 32 and 64 bit integers. These are not directly consumable in Python and must be consumed by aGenerator
or similar object that supports lowlevel access.State and Seeding
The
SFC64
state vector consists of 4 unsigned 64bit values. The last is a 64bit counter that increments by 1 each iteration.The input seed is processed by
SeedSequence
to generate the first 3 values, then theSFC64
algorithm is iterated a small number of times to mix.Compatibility Guarantee
SFC64
makes a guarantee that a fixed seed will always produce the same random integer stream.References
[1] “PractRand” [2] “Random Invertible Mapping Statistics”