c++11 Random number generator in subfunction

Question

I am learning parallel computing at the moment, and for a exercise I need random number generators in parallel. But I do not seem to be able to use a RNG in subroutines, so that they return different numbers. The following code is the simplest test I made, while figuring out how to do this. For each iteration it returns the same number, but I do not know why. Would you please explain what I do not understand.

#include <iostream>
#include <random>
void morerandom(double& num, double seednum)
{
     std::mt19937 mt;
     mt.seed(seednum);
     std::uniform_real_distribution<double> ureal_d(0.,1.);
     num = ureal_d(mt);
}


int main()
{
    std::vector<double> nums = {0.1, 0.4, 0.3, 0.3, 0.1};
    std::vector<double> results(5,0.);

    for (unsigned k=0; k<5; k++)
    {
        morerandom(results[k], nums[k]);
        std::cout << results[k] << std::endl;
    }

    return 0;
}

Answer 1

seed的参数应该是int或其他整数类型 ，由于从double转换为int ，因此总是使用0作为种子。