HORIZON HASKELLDocslts/ghc-9.10.xc74966e2026-09-27Search names, modules, packages, or :: a typeCtrl K

GHC 9.10.3 · lts/ghc-9.10.x · c74966e · 2026-09-27

Modulesplitmix-0.1.3.1Haskell2010

System.Random.SplitMix

SplitMix is a splittable pseudorandom number generator (PRNG) that is quite fast.

Guy L. Steele, Jr., Doug Lea, and Christine H. Flood. 2014. Fast splittable pseudorandom number generators. In Proceedings of the 2014 ACM International Conference on Object Oriented Programming Systems Languages & Applications (OOPSLA '14). ACM, New York, NY, USA, 453-472. DOI: https://doi.org/10.1145/2660193.2660195

The paper describes a new algorithm SplitMix for splittable pseudorandom number generator that is quite fast: 9 64 bit arithmetic/logical operations per 64 bits generated.

SplitMix is tested with two standard statistical test suites (DieHarder and TestU01, this implementation only using the former) and it appears to be adequate for "everyday" use, such as Monte Carlo algorithms and randomized data structures where speed is important.

In particular, it should not be used for cryptographic or security applications, because generated sequences of pseudorandom values are too predictable (the mixing functions are easily inverted, and two successive outputs suffice to reconstruct the internal state).

  • 1 type
  • 18 values
  • Packagesplitmix-0.1.3.1
  • Exports19
  • LanguageHaskell2010
  • LicenceBSD-3-Clause
  • SourceSplitMix.hs
datadata SMGen
#

SplitMix generator state.

Instances3Read, Show, NFData
  • Read SMGenDefined in splitmix-0.1.3.1 · System.Random.SplitMix
    Example1 expression
    readMaybe "SMGen 1 1" :: Maybe SMGenJust (SMGen 1 1)
    Example1 expression
    readMaybe "SMGen 1 2" :: Maybe SMGenNothing
    Example1 expression
    readMaybe (show (mkSMGen 42)) :: Maybe SMGenJust (SMGen 9297814886316923340 13679457532755275413)
  • Show SMGenDefined in splitmix-0.1.3.1 · System.Random.SplitMix
  • NFData SMGenDefined in splitmix-0.1.3.1 · System.Random.SplitMix
valuenextWord64 :: SMGen -> (Word64, SMGen)
#

Generate a Word64.

Example1 expression
take 3 $ map (printf "%x") $ unfoldr (Just . nextWord64) (mkSMGen 1337) :: [String]["b5c19e300e8b07b3","d600e0e216c0ac76","c54efc3b3cc5af29"]
valuenextDouble :: SMGen -> (Double, SMGen)
#

Generate a Double in [0, 1) range.

Example1 expression
take 8 $ map (printf "%0.3f") $ unfoldr (Just . nextDouble) (mkSMGen 1337) :: [String]["0.710","0.836","0.771","0.409","0.297","0.527","0.589","0.067"]
valuenextFloat :: SMGen -> (Float, SMGen)
#

Generate a Float in [0, 1) range.

Example1 expression
take 8 $ map (printf "%0.3f") $ unfoldr (Just . nextFloat) (mkSMGen 1337) :: [String]["0.057","0.089","0.237","0.383","0.680","0.320","0.826","0.007"]

Generation

4 declarations
valuebitmaskWithRejection64 :: Word64 -> SMGen -> (Word64, SMGen)
#

Bitmask with rejection method of generating subrange of Word64.

bitmaskWithRejection64 w64 generates random numbers in closed-open range of [0, w64).

Example1 expression
take 20 $ unfoldr (Just . bitmaskWithRejection64 5) (mkSMGen 1337)[3,1,4,1,2,3,1,1,0,3,4,2,3,0,2,3,3,4,1,0]
valuebitmaskWithRejection64' :: Word64 -> SMGen -> (Word64, SMGen)
#

Bitmask with rejection method of generating subrange of Word64.

bitmaskWithRejection64' w64 generates random numbers in closed-closed range of [0, w64].

Example1 expression
take 20 $ unfoldr (Just . bitmaskWithRejection64' 5) (mkSMGen 1337)[3,1,4,1,2,3,1,1,0,3,4,5,2,3,0,2,3,5,3,4]

Initialisation

6 declarations
valuemkSMGen :: Word64 -> SMGen
#

Preferred way to deterministically construct SMGen.

Example1 expression
mkSMGen 42SMGen 9297814886316923340 13679457532755275413