c++ - Better random algorithm?

Question

I'm making a game in C++ and it involves filling tiles with random booleans (either yes or no) whether it is yes or no is decided by rand() % 1. It doesn't feel very random.

I'm using srand with ctime at startup, but it seems like the same patterns are coming up.

Are there any algorithms that will create very random numbers? Or any suggestions on how I could improve rand()?

Answer 1

True randomness often doesn't seem very random. Do expect to see odd runs.

But at least one immediate thing you can do to help is to avoid using just the lowest-order bit. To quote Numerical Recipes in C:

If you want to generate a random integer between 1 and 10, you should always do it by using high-order bits, as in

j = 1 + (int) (10.0 * (rand() / (RAND_MAX + 1.0)));

and never by anything resembling

j = 1 + (rand() % 10);

(which uses lower-order bits).

Also, you might consider using a different RNG with better properties instead. The Xorshift algorithm is a nice alternative. It's speedy and compact at just a few lines of C, and should be good enough statistically for nearly any game.