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pub struct Lcg128CmDxsm64 { /* private fields */ }
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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

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 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

Returns a copy of the value. Read more
Performs copy-assignment from source. Read more
Formats the value using the given formatter. Read more
This method tests for self and other values to be equal, and is used by ==. Read more
This method tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason. Read more
Return the next random u32. Read more
Return the next random u64. Read more
Fill dest with random data. Read more
Fill dest entirely with random data. Read more

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.

Seed type, which is restricted to types mutably-dereferenceable as u8 arrays (we recommend [u8; N] for some N). Read more
Create a new PRNG using a u64 seed. Read more
Create a new PRNG seeded from another Rng. Read more
Creates a new instance of the RNG seeded via getrandom. Read more

Auto Trait Implementations

Blanket Implementations

Gets the TypeId of self. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The resulting type after obtaining ownership.
Creates owned data from borrowed data, usually by cloning. Read more
Uses borrowed data to replace owned data, usually by cloning. Read more
The type returned in the event of a conversion error.
Performs the conversion.
The type returned in the event of a conversion error.
Performs the conversion.