xorshift128plus PRNG that mimics System.Random

Faster with much better quality random numbers than System.Random. See https://en.wikipedia.org/wiki/Xorshift

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type XorshiftPRNG(seed) =
    let mutable s : uint64[] = Array.zeroCreate 2

    do s.[1] <- uint64 seed

    let sample() =
        let mutable x = s.[0]
        let y = s.[1]
        s.[0] <- y
        x <- x ^^^ (x <<< 23)
        s.[1] <- x ^^^ y ^^^ (x >>> 17) ^^^ (y >>> 26)
        let smpl = s.[1] + y
        if smpl = System.UInt64.MaxValue then smpl - 1UL else smpl

    member x.NextDouble() = (float (sample())) / float System.UInt64.MaxValue

    member x.Next(max) = 
        if max < 0 then failwith "max < 0"
        x.NextDouble() * (float max) |> int

    member x.Next(min:int,max:int) = 
        if min > max then failwith "min > max" 
        let r = max - min in (float r) * (x.NextDouble()) + (float min) |> int

    new()=XorshiftPRNG(System.Environment.TickCount)

Multiple items
type XorshiftPRNG =
  new : unit -> XorshiftPRNG
  new : seed:int -> XorshiftPRNG
  member Next : max:int -> int
  member Next : min:int * max:int -> int
  member NextDouble : unit -> float

Full name: Script.XorshiftPRNG

--------------------
new : unit -> XorshiftPRNG
new : seed:int -> XorshiftPRNG

val seed : int

val mutable s : uint64 []

Multiple items
val uint64 : value:'T -> uint64 (requires member op_Explicit)

Full name: Microsoft.FSharp.Core.Operators.uint64

--------------------
type uint64 = System.UInt64

Full name: Microsoft.FSharp.Core.uint64

module Array

from Microsoft.FSharp.Collections

val zeroCreate : count:int -> 'T []

Full name: Microsoft.FSharp.Collections.Array.zeroCreate

val sample : (unit -> uint64)

val mutable x : uint64

val y : uint64

val smpl : uint64

namespace System

type UInt64 =
  struct
    member CompareTo : value:obj -> int + 1 overload
    member Equals : obj:obj -> bool + 1 overload
    member GetHashCode : unit -> int
    member GetTypeCode : unit -> TypeCode
    member ToString : unit -> string + 3 overloads
    static val MaxValue : uint64
    static val MinValue : uint64
    static member Parse : s:string -> uint64 + 3 overloads
    static member TryParse : s:string * result:uint64 -> bool + 1 overload
  end

Full name: System.UInt64

field uint64.MaxValue = 18446744073709551615UL

val x : XorshiftPRNG

member XorshiftPRNG.NextDouble : unit -> float

Full name: Script.XorshiftPRNG.NextDouble

Multiple items
val float : value:'T -> float (requires member op_Explicit)

Full name: Microsoft.FSharp.Core.Operators.float

--------------------
type float = System.Double

Full name: Microsoft.FSharp.Core.float

--------------------
type float<'Measure> = float

Full name: Microsoft.FSharp.Core.float<_>

member XorshiftPRNG.Next : max:int -> int

Full name: Script.XorshiftPRNG.Next

val max : int

val failwith : message:string -> 'T

Full name: Microsoft.FSharp.Core.Operators.failwith

member XorshiftPRNG.NextDouble : unit -> float

Multiple items
val int : value:'T -> int (requires member op_Explicit)

Full name: Microsoft.FSharp.Core.Operators.int

--------------------
type int = int32

Full name: Microsoft.FSharp.Core.int

--------------------
type int<'Measure> = int

Full name: Microsoft.FSharp.Core.int<_>

member XorshiftPRNG.Next : min:int * max:int -> int

Full name: Script.XorshiftPRNG.Next

val min : int

val r : int

type Environment =
  static member CommandLine : string
  static member CurrentDirectory : string with get, set
  static member Exit : exitCode:int -> unit
  static member ExitCode : int with get, set
  static member ExpandEnvironmentVariables : name:string -> string
  static member FailFast : message:string -> unit + 1 overload
  static member GetCommandLineArgs : unit -> string[]
  static member GetEnvironmentVariable : variable:string -> string + 1 overload
  static member GetEnvironmentVariables : unit -> IDictionary + 1 overload
  static member GetFolderPath : folder:SpecialFolder -> string + 1 overload
  ...
  nested type SpecialFolder
  nested type SpecialFolderOption

Full name: System.Environment

property System.Environment.TickCount: int

Raw view Test code New version

More information

Link:	http://fssnip.net/7Rb
Posted:	8 years ago
Author:	Faisal Waris
Tags:	prng, pseudo-random number generator, random