Standard rand()
function gives numbers not big enough for me: I need unsigned long long
ones. How do we get really big random numbers? I tried modifying a simple hash function but it's too big, takes too long to run and never produces numbers which are less than 1e5!!
You can easily do this with std::uniform_int_distribution<unsigned long long>
.
Simple example code (taken from here, modified to use unsigned long long
):
#include <random>
#include <iostream>
int main()
{
std::random_device rd;
std::mt19937 gen(rd());
std::uniform_int_distribution<unsigned long long> dis(lowerBorder, upperBorder);
for (int n=0; n<10; ++n)
std::cout << dis(gen) << ' ';
std::cout << '\n';
}
Note that the seeding of the mersenne twister as done here for demo purposes is not perfect, for example see here.