How do I generate thread-safe uniform random numbers?

Question

My program needs to generate many random integers in some range (int min, int max). Each call will have a different range. What is a good (preferably thread-safe) w

Answer 1

Have you tried this?

int intRand(const int & min, const int & max) {
    static thread_local std::mt19937 generator;
    std::uniform_int_distribution distribution(min,max);
    return distribution(generator);
}

Distributions are extremely cheap (they will be completely inlined by the optimiser so that the only remaining overhead is the actual random number rescaling). Don’t be afraid to regenerate them as often as you need – in fact, resetting them would conceptually be no cheaper (which is why that operation doesn’t exist).

The actual random number generator, on the other hand, is a heavy-weight object carrying a lot of state and requiring quite some time to be constructed, so that should only be initialised once per thread (or even across threads, but then you’d need to synchronise access which is more costly in the long run).