为什么我的第一个伪随机整数总是为零？

Question

我有多个循环运行并尝试在每次运行中创建一个不同但伪随机的整数.不幸的是,创建的第一个数字始终为0.

有趣的是,这只是通过生成随机整数的情况std::uniform_int_distribution<int>.如果我替换它,std::uniform_real_distribution<double>我获得了所需的行为.

创建种子时是否有任何特殊规则或为什么第一个生成的整数始终为0？

下面是我的问题的最小例子:

#include <iostream>
#include <random>

int main() {

    int number_of_runs = 5;

    for (int i = 0; i != number_of_runs; ++i) {

        // create random engine
        std::default_random_engine my_generator;
        unsigned my_seed = i; // should be pseudo-random, but different for every run
        my_generator.seed(my_seed);

        // create distribution
        int upper_limit = (i+1)*10; // only example, but different for every run
        std::uniform_int_distribution<int> my_distribution(0, upper_limit);

        // create random numbers
        std::cout << "run #" << i+1 << "\n";
        std::cout << "random 1: " << my_distribution(my_generator) << "\n";
        std::cout << "random 2: " << my_distribution(my_generator) << "\n";
        std::cout << "random 3: " << my_distribution(my_generator) << "\n";
        std::cout << "random 4: " << my_distribution(my_generator) << "\n";
        std::cout << "random 5: " << my_distribution(my_generator) << "\n" << std::endl;

    }

    return 0;
}

结果是例如:

run #1:
random 1: 0
random 2: 1
random 3: 8
random 4: 5
random 5: 5

run #2
random 1: 0
random 2: 2
random 3: 15
random 4: 9
random 5: 11

run #3
random 1: 0
random 2: 8
random 3: 15
random 4: 28
random 5: 2

run #4
random 1: 0
random 2: 16
random 3: 10
random 4: 15
random 5: 24

run #5
random 1: 0
random 2: 26
random 3: 1
random 4: 42
random 5: 6