class numpy.random.pcg64.PCG64(seed_seq=None)
BitGenerator for the PCG-64 pseudo-random number generator.
Parameters: |
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PCG-64 is a 128-bit implementation of O’Neill’s permutation congruential generator ([1], [2]). PCG-64 has a period of and supports advancing an arbitrary number of steps as well as streams. The specific member of the PCG family that we use is PCG XSL RR 128/64 as described in the paper ([2]).
PCG64
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 a Generator
or similar object that supports low-level access.
Supports the method advance
to advance the RNG an arbitrary number of steps. The state of the PCG-64 RNG is represented by 2 128-bit unsigned integers.
State and Seeding
The PCG64
state vector consists of 2 unsigned 128-bit values, which are represented externally as Python ints. One is the state of the PRNG, which is advanced by a linear congruential generator (LCG). The second is a fixed odd increment used in the LCG.
The input seed is processed by SeedSequence
to generate both values. The increment is not independently settable.
Parallel Features
The preferred way to use a BitGenerator in parallel applications is to use the SeedSequence.spawn
method to obtain entropy values, and to use these to generate new BitGenerators:
>>> from numpy.random import Generator, PCG64, SeedSequence >>> sg = SeedSequence(1234) >>> rg = [Generator(PCG64(s)) for s in sg.spawn(10)]
Compatibility Guarantee
PCG64
makes a guarantee that a fixed seed and will always produce the same random integer stream.
[1] | “PCG, A Family of Better Random Number Generators” |
[2] | (1, 2) O’Neill, Melissa E. “PCG: A Family of Simple Fast Space-Efficient Statistically Good Algorithms for Random Number Generation” |
state | Get or set the PRNG state |
advance (delta) | Advance the underlying RNG as-if delta draws have occurred. |
jumped ([jumps]) | Returns a new bit generator with the state jumped. |
cffi | CFFI interface |
ctypes | ctypes interface |
© 2005–2019 NumPy Developers
Licensed under the 3-clause BSD License.
https://docs.scipy.org/doc/numpy-1.17.0/reference/random/bit_generators/pcg64.html