.. index:: single: fast_random(Algorithm) .. _fast_random/1:

.. rst-class:: right

object

fast_random(Algorithm)

• Algorithm - Random number generator algorithm. One of as183, splitmix64, xoshiro128pp, xoshiro128ss, xoshiro256pp, xoshiro256ss, well512a. Fast portable random number generator predicates.

  | Availability: | logtalk_load(random(loader))

  | Author: Paulo Moura | Version: 3:0:0 | Date: 2026-02-23

  | Compilation flags: | static, context_switching_calls

  | Implements: | public :ref:`pseudo_random_protocol <pseudo_random_protocol/0>` | public :ref:`sampling_protocol <sampling_protocol/0>` | Uses: | :ref:`list <list/0>`

  | Remarks:

  • Single random number generator: This object provides a faster version of the random library object but does not support being extended to define multiple random number generators.
  • Randomness: Loading this object always initializes the random generator seed to the same value, thus providing a pseudo random number generator. The randomize/1 predicate can be used to initialize the seed with a random value.
  • as183: Algorithm AS 183 from Applied Statistics. 32-bit PRNG with period 2^60. Not cryptographically secure.
  • xoshiro128pp: Xoshiro128++ random number generator. 32-bit state-of-the-art PRNG with period 2^128-1. Algorithm by David Blackman and Sebastiano Vigna.
  • xoshiro128ss: Xoshiro128** random number generator. 32-bit PRNG with period 2^128-1. Algorithm by David Blackman and Sebastiano Vigna.
  • xoshiro256pp: Xoshiro256++ random number generator. 64-bit state-of-the-art PRNG with period 2^256-1. Algorithm by David Blackman and Sebastiano Vigna.
  • xoshiro256ss: Xoshiro256** random number generator. 64-bit PRNG with period 2^256-1. Algorithm by David Blackman and Sebastiano Vigna.
  • splitmix64: SplitMix64 random number generator. 64-bit PRNG primarily used for seeding other generators. Algorithm by Guy L. Steele Jr. et al.
  • well512a: WELL512a 16x32-bit state-of-the-art PRNG with period 2^512-1. Algorithm by by François Panneton, Pierre L'Ecuyer, and Makoto Matsumoto.
  • Algorithms backend compatibility: The SplitMix64, Xoshiro256++, and Xoshiro256** algorithms require support for unbound integer arithmetic.

  | Inherited public predicates: |  :ref:`sampling_protocol/0::bernoulli/2`  :ref:`sampling_protocol/0::beta/3`  :ref:`random_protocol/0::between/3`  :ref:`sampling_protocol/0::binomial/3`  :ref:`sampling_protocol/0::chi_squared/2`  :ref:`sampling_protocol/0::circular_uniform_cartesian/3`  :ref:`sampling_protocol/0::circular_uniform_polar/3`  :ref:`sampling_protocol/0::dirichlet/2`  :ref:`random_protocol/0::enumerate/2`  :ref:`sampling_protocol/0::exponential/2`  :ref:`sampling_protocol/0::fisher/3`  :ref:`sampling_protocol/0::gamma/3`  :ref:`sampling_protocol/0::geometric/2`  :ref:`pseudo_random_protocol/0::get_seed/1`  :ref:`sampling_protocol/0::gumbel/3`  :ref:`sampling_protocol/0::hypergeometric/4`  :ref:`sampling_protocol/0::logistic/3`  :ref:`sampling_protocol/0::lognormal/3`  :ref:`sampling_protocol/0::logseries/2`  :ref:`random_protocol/0::maybe/0`  :ref:`random_protocol/0::maybe/1`  :ref:`random_protocol/0::maybe/2`  :ref:`random_protocol/0::maybe_call/1`  :ref:`random_protocol/0::maybe_call/2`  :ref:`random_protocol/0::member/2`  :ref:`sampling_protocol/0::normal/3`  :ref:`random_protocol/0::permutation/2`  :ref:`sampling_protocol/0::poisson/2`  :ref:`sampling_protocol/0::power/2`  :ref:`random_protocol/0::random/1`  :ref:`random_protocol/0::random/3`  :ref:`random_protocol/0::randseq/4`  :ref:`random_protocol/0::randset/4`  :ref:`random_protocol/0::select/3`  :ref:`random_protocol/0::select/4`  :ref:`random_protocol/0::sequence/4`  :ref:`random_protocol/0::set/4`  :ref:`pseudo_random_protocol/0::set_seed/1`  :ref:`sampling_protocol/0::standard_cauchy/3`  :ref:`sampling_protocol/0::standard_exponential/1`  :ref:`sampling_protocol/0::standard_gamma/2`  :ref:`sampling_protocol/0::standard_normal/1`  :ref:`sampling_protocol/0::standard_t/2`  :ref:`random_protocol/0::swap/2`  :ref:`random_protocol/0::swap_consecutive/2`  :ref:`sampling_protocol/0::triangular/4`  :ref:`sampling_protocol/0::uniform/1`  :ref:`sampling_protocol/0::uniform/3`  :ref:`sampling_protocol/0::von_mises/3`  :ref:`sampling_protocol/0::wald/3`  :ref:`sampling_protocol/0::weibull/3`  

  .. contents:: :local: :backlinks: top

Public predicates

.. index:: reset_seed/0 .. _fast_random/1::reset_seed/0:

reset_seed/0 ^^^^^^^^^^^^^^^^

Resets the random generator seed to its default value. Use get_seed/1 and set_seed/1 instead if you need reproducibility.

| Compilation flags: | static, synchronized

| Mode and number of proofs: | reset_seed - one

---

.. index:: randomize/1 .. _fast_random/1::randomize/1:

randomize/1 ^^^^^^^^^^^^^^^

Randomizes the random generator using a positive integer to compute a new seed. Use of a large integer is recommended. In alternative, when using a small integer argument, discard the first dozen random values.

| Compilation flags: | static, synchronized

| Template: | randomize(Seed) | Mode and number of proofs: | randomize(+positive_integer) - one

---

Protected predicates

(no local declarations; see entity ancestors if any)

Private predicates

.. index:: seed_/2 .. _fast_random/1::seed_/2:

seed_/2 ^^^^^^^^^^^

Stores the current random generator seed values (a ground but otherwise opaque term).

| Compilation flags: | dynamic

| Template: | seed_(Algorithm,Seed) | Mode and number of proofs: | seed_(+atom,-ground) - one

---

Operators

(none)

.. seealso::

:ref:`fast_random <fast_random/0>`, :ref:`random(Algorithm) <random/1>`, :ref:`random <random/0>`, :ref:`backend_random <backend_random/0>`