Pseudo-random numbers/Splitmix64: Difference between revisions

=={{header|Nim}}==

<lang Nim>import math, sequtils, strutils

const Two64 = 2.0^64

type Splitmix64 = object

state: uint64

func initSplitmix64(seed: uint64): Splitmix64 =

## Initialize a Splitmiax64 PRNG.

Splitmix64(state: seed)

func nextInt(r: var Splitmix64): uint64 =

## Return the next pseudorandom integer (actually a uint64 value).

r.state += 0x9e3779b97f4a7c15u

var z = r.state

z = (z xor z shr 30) * 0xbf58476d1ce4e5b9u

z = (z xor z shr 27) * 0x94d049bb133111ebu

result = z xor z shr 31

func nextFloat(r: var Splitmix64): float =

## Retunr the next pseudorandom float (between 0.0 and 1.0 excluded).

r.nextInt().float / Two64

when isMainModule:

echo "Seed = 1234567:"

var prng = initSplitmix64(1234567)

for i in 1..5:

echo i, ": ", ($prng.nextInt).align(20)

echo "\nSeed = 987654321:"

var counts: array[0..4, int]

prng = initSplitmix64(987654321)

for _ in 1..100_000:

inc counts[int(prng.nextFloat * 5)]

echo toSeq(counts.pairs).mapIt(($it[0]) & ": " & ($it[1])).join(", "</lang>

{{out}}

<pre>Seed = 1234567:

1: 6457827717110365317

2: 3203168211198807973

3: 9817491932198370423

4: 4593380528125082431

5: 16408922859458223821

Seed = 987654321:

0: 20027, 1: 19892, 2: 20073, 3: 19978, 4: 20030</pre>