Struct rand_pcg::Lcg128Xsl64 [−][src]
pub struct Lcg128Xsl64 { /* fields omitted */ }
Expand description
A PCG random number generator (XSL RR 128/64 (LCG) variant).
Permuted Congruential Generator with 128-bit state, internal Linear Congruential Generator, and 64-bit output via “xorshift low (bits), random rotation” output function.
This is a 128-bit LCG with explicitly chosen stream with the PCG-XSL-RR
output function. This combination is the standard pcg64
.
Despite the name, this implementation uses 32 bytes (256 bit) space
comprising 128 bits of state and 128 bits stream selector. These are both
set by SeedableRng
, using a 256-bit seed.
Note that two generators with different stream parameters may be closely correlated.
Implementations
Multi-step advance functions (jump-ahead, jump-back)
The method used here is based on Brown, “Random Number Generation with Arbitrary Stride,”, Transactions of the American Nuclear Society (Nov. 1994). The algorithm is very similar to fast exponentiation.
Even though delta is an unsigned integer, we can pass a signed integer to go backwards, it just goes “the long way round”.
Using this function is equivalent to calling next_64()
delta
number of times.
Construct an instance compatible with PCG seed and stream.
Note that two generators with different stream parameters may be closely correlated.
PCG specifies the following default values for both parameters:
state = 0xcafef00dd15ea5e5
stream = 0xa02bdbf7bb3c0a7ac28fa16a64abf96
Trait Implementations
This method tests for self
and other
values to be equal, and is used
by ==
. Read more
This method tests for !=
.
We use a single 255-bit seed to initialise the state and select a stream.
One seed
bit (lowest bit of seed[8]
) is ignored.