GHC 10.0.0.20260917 · lts/ghc-10.0.x · 2b27632 · 2026-10-31
Modulehedgehog-1.7Haskell2010
This is a port of "Fast Splittable Pseudorandom Number Generators" by Steele et. al. [1].
The paper's algorithm provides decent randomness for most purposes but sacrifices cryptographic-quality randomness in favor of speed. The original implementation is tested with DieHarder and BigCrush; see the paper for details.
This implementation, originally from [2], is a port from the paper.
It also takes in to account the SplittableRandom.java source code in OpenJDK v8u40-b25 as well as splittable_random.ml in Jane Street's standard library overlay (kernel) v113.33.03, and Random.fs in FsCheck v3.
Other than the choice of initial seed for from this port should be faithful.
Guy L. Steele, Jr., Doug Lea, Christine H. Flood Fast splittable pseudorandom number generators Comm ACM, 49(10), Oct 2014, pp453-472.
Nikos Baxevanis https://github.com/moodmosaic/SplitMix/blob/master/SplitMix.hs
A splittable random number generator.
Eq SeedDefined in hedgehog-1.7 · Hedgehog.Internal.SeedOrd SeedDefined in hedgehog-1.7 · Hedgehog.Internal.SeedRead SeedDefined in hedgehog-1.7 · Hedgehog.Internal.SeedShow SeedDefined in hedgehog-1.7 · Hedgehog.Internal.SeedRandomGen SeedDefined in hedgehog-1.7 · Hedgehog.Internal.SeedLift SeedDefined in hedgehog-1.7 · Hedgehog.Internal.SeedCreate a random Seed using an effectful source of randomness.
Splits a random number generator in to two.
Generate a random Integer in the [inclusive,inclusive] range.
Generate a random Double in the [inclusive,exclusive) range.
These functions are exported in case you need them in a pinch, but are not part of the public API and may change at any time, even as part of a minor update.
A predefined gamma value's needed for initializing the "root" instances of Seed. That is, instances not produced by splitting an already existing instance.
We choose: the odd integer closest to 2^64/φ, where φ = (1 + √5)/2 is
the golden ratio.
Generate a random Word64.
Generate a random Word32.