A good random number generator for C

Question

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.

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/

Comments

[UmNyobe]

no, he is giving a candidate. +1 btw, never heard of Mersenne before

[Void Star]

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]

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]

Considering the fact that this actually turned my non-working rand()-based algorithm into something I could actually work with, +1!

[Void Star]

underappreciated answer here - I've used these in a couple projects so far and they work great, with such a simple implementation!