c - implementation of rand()

Question

I am writing some embedded code in C and need to use the rand() function. Unfortunately, rand() is not supported in the library for the controller. I need a simple implementation that is fast, but more importantly has little space overhead, that produces relatively high-quality random numbers. Does anyone know which algorithm to use or sample code?

EDIT: It's for image processing, so "relatively high quality" means decent cycle length and good uniform properties.

Answer 1

Check out this collection of random number generators from George Marsaglia. He's a leading expert in random number generation, so I'd be confident using anything he recommends. The generators in that list are tiny, some requiring only a couple unsigned longs as state.

Marsaglia's generators are definitely "high quality" by your standards of long period and good uniform distribution. They pass stringent statistical tests, though they wouldn't do for cryptography.