Struct rand_pcg::Lcg128CmDxsm64
source · pub struct Lcg128CmDxsm64 { /* private fields */ }
Expand description
A PCG random number generator (CM DXSM 128/64 (LCG) variant).
Permuted Congruential Generator with 128-bit state, internal Linear Congruential Generator, and 64-bit output via “double xorshift multiply” output function.
This is a 128-bit LCG with explicitly chosen stream with the PCG-DXSM
output function. This corresponds to pcg_engines::cm_setseq_dxsm_128_64
from pcg_cpp and PCG64DXSM
from NumPy.
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 while two generators with different stream parameter may be closely correlated, this is mitigated by the DXSM output function.
Implementations§
source§impl Lcg128CmDxsm64
impl Lcg128CmDxsm64
sourcepub fn advance(&mut self, delta: u128)
pub fn advance(&mut self, delta: u128)
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.
sourcepub fn new(state: u128, stream: u128) -> Self
pub fn new(state: u128, stream: u128) -> Self
Construct an instance compatible with PCG seed and stream.
Note that the highest bit of the stream
parameter is discarded
to simplify upholding internal invariants.
Note that while two generators with different stream parameter may be closely correlated, this is mitigated by the DXSM output function.
PCG specifies the following default values for both parameters:
state = 0xcafef00dd15ea5e5
stream = 0xa02bdbf7bb3c0a7ac28fa16a64abf96
Trait Implementations§
source§impl Clone for Lcg128CmDxsm64
impl Clone for Lcg128CmDxsm64
source§fn clone(&self) -> Lcg128CmDxsm64
fn clone(&self) -> Lcg128CmDxsm64
1.0.0 · source§fn clone_from(&mut self, source: &Self)
fn clone_from(&mut self, source: &Self)
source
. Read moresource§impl Debug for Lcg128CmDxsm64
impl Debug for Lcg128CmDxsm64
source§impl<'de> Deserialize<'de> for Lcg128CmDxsm64
impl<'de> Deserialize<'de> for Lcg128CmDxsm64
source§fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>where
__D: Deserializer<'de>,
fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>where __D: Deserializer<'de>,
source§impl PartialEq<Lcg128CmDxsm64> for Lcg128CmDxsm64
impl PartialEq<Lcg128CmDxsm64> for Lcg128CmDxsm64
source§fn eq(&self, other: &Lcg128CmDxsm64) -> bool
fn eq(&self, other: &Lcg128CmDxsm64) -> bool
self
and other
values to be equal, and is used
by ==
.source§impl RngCore for Lcg128CmDxsm64
impl RngCore for Lcg128CmDxsm64
source§fn fill_bytes(&mut self, dest: &mut [u8])
fn fill_bytes(&mut self, dest: &mut [u8])
dest
with random data. Read moresource§fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error>
fn try_fill_bytes(&mut self, dest: &mut [u8]) -> Result<(), Error>
dest
entirely with random data. Read moresource§fn read_adapter(&mut self) -> RngReadAdapter<'_, Self>where
Self: Sized,
fn read_adapter(&mut self) -> RngReadAdapter<'_, Self>where Self: Sized,
RngCore
to a RngReadAdapter
.source§impl SeedableRng for Lcg128CmDxsm64
impl SeedableRng for Lcg128CmDxsm64
source§fn from_seed(seed: Self::Seed) -> Self
fn from_seed(seed: Self::Seed) -> Self
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.
§type Seed = [u8; 32]
type Seed = [u8; 32]
u8
arrays (we recommend [u8; N]
for some N
). Read moresource§fn seed_from_u64(state: u64) -> Self
fn seed_from_u64(state: u64) -> Self
u64
seed. Read moresource§fn from_rng<R>(rng: R) -> Result<Self, Error>where
R: RngCore,
fn from_rng<R>(rng: R) -> Result<Self, Error>where R: RngCore,
Rng
. Read more