Safe Haskell	None
Language	Haskell98

Hedgehog.Internal.Seed

Contents

Internal

Description

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

Synopsis

data Seed = Seed {
- seedValue :: !Word64
- seedGamma :: !Word64
}
random :: MonadIO m => m Seed
from :: Word64 -> Seed
split :: Seed -> (Seed, Seed)
nextInteger :: Integer -> Integer -> Seed -> (Integer, Seed)
nextDouble :: Double -> Double -> Seed -> (Double, Seed)
goldenGamma :: Word64
nextWord64 :: Seed -> (Word64, Seed)
nextWord32 :: Seed -> (Word32, Seed)
mix64 :: Word64 -> Word64
mix64variant13 :: Word64 -> Word64
mix32 :: Word64 -> Word32
mixGamma :: Word64 -> Word64

Documentation

data Seed #

A splittable random number generator.

Constructors

Seed
Fields seedValue :: !Word64 seedGamma :: !Word64 must be an odd number

Instances

Eq Seed #
Instance details Defined in Hedgehog.Internal.Seed Methods (==) :: Seed -> Seed -> Bool # (/=) :: Seed -> Seed -> Bool #
Ord Seed #
Instance details Defined in Hedgehog.Internal.Seed Methods compare :: Seed -> Seed -> Ordering # (<) :: Seed -> Seed -> Bool # (<=) :: Seed -> Seed -> Bool # (>) :: Seed -> Seed -> Bool # (>=) :: Seed -> Seed -> Bool # max :: Seed -> Seed -> Seed # min :: Seed -> Seed -> Seed #
Read Seed #
Instance details Defined in Hedgehog.Internal.Seed Methods readsPrec :: Int -> ReadS Seed # readList :: ReadS [Seed] # readPrec :: ReadPrec Seed # readListPrec :: ReadPrec [Seed] #
Show Seed #
Instance details Defined in Hedgehog.Internal.Seed Methods showsPrec :: Int -> Seed -> ShowS # show :: Seed -> String # showList :: [Seed] -> ShowS #
RandomGen Seed #
Instance details Defined in Hedgehog.Internal.Seed Methods next :: Seed -> (Int, Seed) # genRange :: Seed -> (Int, Int) # split :: Seed -> (Seed, Seed) #

random :: MonadIO m => m Seed #

Create a random Seed using an effectful source of randomness.

from :: Word64 -> Seed #

Create a Seed using a Word64.

split :: Seed -> (Seed, Seed) #

Splits a random number generator in to two.

nextInteger :: Integer -> Integer -> Seed -> (Integer, Seed) #

Generate a random Integer in the [inclusive,inclusive] range.

nextDouble :: Double -> Double -> Seed -> (Double, Seed) #

Generate a random Double in the [inclusive,exclusive) range.

Internal

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.

goldenGamma :: Word64 #

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.

nextWord64 :: Seed -> (Word64, Seed) #

Generate a random Word64.

nextWord32 :: Seed -> (Word32, Seed) #

Generate a random Word32.

mix64 :: Word64 -> Word64 #

mix64variant13 :: Word64 -> Word64 #

mix32 :: Word64 -> Word32 #

mixGamma :: Word64 -> Word64 #