Random

A collection of Pseudo Random Number Generators (PRNG) algorithms for the Crystal language. Each implementation implements the Random interface.

Continuation of the crystal-random shard.

Installation

Add the shard:

dependencies:
  random:
    github: ysbaddaden/random.cr

Usage

You may require random/all to include all algorithms, but it is recommended to specify the chosen algorithms such as random/xorshift128plus for example.

Algorithms

Sorted by increasing state.

PRNG	w	speed (x86)	speed (arm)	State	Splittable	Cryptography	TestU01	Comment
Random::XorShift32	32-bit	4.01ns	3.24ns	2$^{32}	No	No	Fails	too many TESTU01 failures
Random::ISAAC (stdlib)	32-bit	8.02ns	8.71ns	2$^{64}	No	Yes	-
Random::PCG32 (stdlib)	32-bit	4.41ns	3.77ns	2$^{64}	No	No	Big Crush
Random::PCG64	64-bit	4.47ns	7.20ns	2$^{64}	No	No	?
Random::SplitMix64	64-bit	3.77ns	4.13ns	2$^{64}	No	No	Big Crush	used to seed XoShiRo128 and XoShiRo256
Random::Splittable	64-bit	3.46ns	3.91ns	2$^{64}	Yes	No	Big Crush
Random::XorShift64	64-bit	3.55ns	2.52ns !	2$^{64}	No	No	Fails
Random::XorShift64Plus	32-bit	4.47ns	3.77ns	2$^{64}	No	No	Small Crush	for Float32 numbers
Random::XorShift64Star	64-bit	3.51ns	3.01ns	2$^{64}	No	No	Fails	for Float64 numbers
Random::XoRoShiRo64StarStar	32-bit	4.75ns	4.10ns	2$^{64}	No	No	Big Crush	all purpose generator
Random::WyRand	64-bit	3.15ns !	5.18ns	2$^{64}	No	No	Big Crush
Random::Lehmer64	64-bit	3.15ns !	5.53ns	2$^{128}	No	No	Big Crush	simplest
Random::Splittable128	64-bit	4.24ns	4.70ns	2$^{128}	Yes	No	Big Crush
Random::XorShift128	32-bit	5.97ns	4.89ns	2$^{128}	No	No	Fails
Random::XorShift128Plus	64-bit	3.38ns	2.91ns	2$^{128}	No	No	?	for Float64 numbers
Random::XoShiRo128StarStar	32-bit	5.23ns	4.15ns	2$^{128}	Yes	No	Big Crush	all purpose generator
Random::XoShiRo128Plus	32-bit	5.04ns	4.28ns	2$^{128}	Yes	No	?	for Float32 numbers
Random::XoShiRo256PlusPlus	64-bit	4.07ns	3.60ns	2$^{256}	Yes	No	Big Crush	all purpose generator
Random::XoShiRo256StarStar	64-bit	3.97ns	3.50ns	2$^{256}	Yes	No	Big Crush	all purpose generator
Random::XoShiRo256Plus	64-bit	3.90ns	3.76ns	2$^{256}	Yes	No	?	for Float64 numbers
Random::XorShift1024Star	64-bit	3.77ns	4.00ns	2$^{1024}	Yes	No	Fails	for massive parallel computations
Random::MT19937	32-bit	6.64ns	5.13ns	2$^{19937}	No	No	Fails	Mersenne Twister (removed from stdlib)

The Plus and Star scrambles for the xorshift family (including xoshiro and xoroshiro) all fail BigCrush, but are still statistically correct enough to generate floating-point numbers (either Float32 or Float64) since their weakest bits are skipped.

The algorithms were benchmarked on an Intel Core i7-4712HQ (Haswell) and an Neoverse-N1 ARM server.

The TESTU01 results are aggregated from the following pages by Sebastiano Vigna and Daniel Lemire, as well as different papers.

• https://prng.di.unimi.it/
• https://github.com/lemire/testingRNG
• https://arxiv.org/pdf/1402.6246
• https://arxiv.org/pdf/1404.0390

TODO:

• [ ] Random::ISAAC64
• [ ] Random::ChaCha12
• [ ] Random::ChaCha20

Maybe also:

• [ ] Random::MWC128
• [ ] Random::MWC256
• [ ] Random::MWC512
• [ ] Random::GMWC128
• [ ] Random::GMWC256
• [ ] Random::WELL512
• [ ] Random::WELL1024
• [ ] Random::WELL19937
• [ ] Random::WELL44497
• [ ] Random::XorWow
• [ ] Random::XoRoShiRo64Star
• [ ] Random::XoRoShiRo128Plus
• [ ] Random::XoRoShiRo128PlusPlus
• [ ] Random::XoRoShiRo128StarStar
• [ ] Random::XoShiRo512Plus
• [ ] Random::XoShiRo512PlusPlus
• [ ] Random::XoShiRo512StarStar
• [ ] Random::XoRoShiRo1024PlusPlus
• [ ] Random::XoRoShiRo1024StarStar
• [ ] Random::XoRoShiRo1024Star

License

Distributed under the Apache-2.0 license.

Contributors

• Julien Portalier (@ysbaddaden)
• crystal-lang The Crystal Lang Team - creator, maintainer