Hawkynt

SplitMix64

SplitMix64 is a very fast pseudo-random number generator designed by Guy L. Steele Jr. and Doug Lea. It uses a simple linear congruential update combined with a high-quality 64-bit mixing function. Commonly used to seed other PRNGs like xorshift*.

Properties

Property	Value
Category	Random Number Generators
Sub-category	Deterministic PRNG
Security status	🎓 Educational Only
Complexity	Beginner
Inventor	Guy L. Steele Jr., Doug Lea
Year	2013
Origin	🇺🇸 United States
Source	algorithms/random/splitmix64.js

Parameters

Parameter	Supported values
Seed sizes	1 byte (8 bits) to 8 bytes (64 bits)

Capabilities

Flag	Value
IsDeterministic	Yes
IsCryptographicallySecure	No

Security

Status: 🎓 Educational Only

No vulnerabilities are recorded for this implementation.

Documentation

• Original Paper: Fast Splittable Pseudorandom Number Generators (OOPSLA 2014)
• Java 8 SplittableRandom Source Code
• Reference Implementation (C)
• Wikipedia: SplitMix64

References

• PCG: A Better Random Number Generator
• TestU01 Statistical Testing Suite

Test vectors

5 vectors ship with this algorithm and run in the test suite. Byte values are hexadecimal.

Vector 1 — Seed 0: First 8 outputs (verified against reference C implementation)

Field	Value
seed	0000000000000000
outputSize	64
input	null
expected	e220a8397b1dcdaf6e789e6aa1b965f4 06c45d188009454ff88bb8a8724c81ec 1b39896a51a8749b53cb9f0c747ea2ea 2c829abe1f4532e1c584133ac916ab3c

Vector 2 — Seed 1: First 5 outputs

Field	Value
seed	0000000000000001
outputSize	40
input	null
expected	910a2dec89025cc1beeb8da1658eec67 f893a2eefb32555e71c18690ee42c90b 71bb54d8d101b5b9

Vector 3 — Seed 42: First 5 outputs (commonly used test seed)

Field	Value
seed	000000000000002a
outputSize	40
input	null
expected	bdd732262feb6e9528efe333b266f103 47526757130f9f52581ce1ff0e4ae394 09bc585a244823f2

Vector 4 — Seed 1234567: First 5 outputs (Rosetta Code test vector)

Field	Value
seed	000000000012d687
outputSize	40
input	null
expected	599ed017fb08fc852c73f08458540fa5 883ebce5a3f27c773fbef740e9177b3f e3b8346708cb5ecd

Vector 5 — Seed 987654321: First 5 outputs (Rosetta Code test vector)

Field	Value
seed	000000003ade68b1
outputSize	40
input	null
expected	b0de530201a9d17ce0b60b3994b35aa2 e048f39adc9ee4a0867287110e89eb48 bfb28d8c1560f051

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