A good random number generator for C


Solution 1

This seems like a good use-case for the Mersenne Twister

  • It's faster than most standard implementations of rand()
  • It has a very long (2^19937 − 1) period
  • It has a pretty high quality - it passes most standardized randomness tests
  • It's public domain

Solution 2

If you are looking for a very fast, decent quality algorithm, you should think about xorshift128+ or xorshift1024*. They are almost as fast as LCGs (according to my comparison they are only 30% slower than simply inline LCG), having much better quality than LCG the same time.

You can find their code and comparison here: http://xorshift.di.unimi.it/

Void Star
Author by

Void Star

Hi, my name is Kyle. I have been interested in science, math, and engineering for (quite literally) as long as I can remember. I am an avid programmer and electronics hobbyist. I attended the University of Washington as an undergraduate in the Electrical Engineering department and now work for Keysight Technologies as a research and development software engineer.

Updated on June 16, 2022


  • Void Star
    Void Star 8 months

    I need a good random number generator for a program I'm writing in C. It's a fractal flame generator, if you're interested. My images were coming out very grainy, even though I had success with the same algorithm in the past. The difference, I finally realized, was the random number generator I was using. Incredibly, it makes an ENORMOUS difference. I'm hoping that an even better random number generator might yield better results. The answer could come in the form of a code sample or a link to a pre-existing random number library. The most important requirements:

    • it should produce relatively high quality streams of random numbers
    • its period must be over ten billion
    • it should be fast enough and offer a good performance trade-off.
  • UmNyobe
    UmNyobe almost 10 years
    no, he is giving a candidate. +1 btw, never heard of Mersenne before
  • Void Star
    Void Star almost 10 years
    Wow, this looks like a REALLY good random number generator. Thanks so much Philipp, I would never have found this on my own.
  • Steve Jessop
    Steve Jessop almost 10 years
    I'm surprised that MT is faster than most implementations of rand(). Isn't rand() commonly an LCG, hence very fast but poor quality?
  • zeboidlund
    zeboidlund over 9 years
    Considering the fact that this actually turned my non-working rand()-based algorithm into something I could actually work with, +1!
  • Void Star
    Void Star about 6 years
    underappreciated answer here - I've used these in a couple projects so far and they work great, with such a simple implementation!