std :: random_device在g ++中不起作用 [英] std::random_device not working in g++

问题描述

我正在Windows中将Mind与g ++一起使用来编译我的c ++代码，如下所示:

I'm using g++ with MinGW in Windows to compile my c++ code, which looks like this:

std::mt19937_64 rng(std::random_device{}());
std::uniform_int_distribution<int> dist(0, words.size() - 1);
std::string curr = words[dist(rng)];

如您所见，

这会从std :: string数组中提取一个随机单词，但是当我选择该单词时，它始终是相同的，我意识到问题出在std :: random_device上，它输出总是相同的数字.

as you can see, this extracts a random word from an array of std::string, but when I optput that word, its always the same, i've realised that the problem lies in std::random_device, which outputs always the same number.

为什么会这样?我该如何解决?

why is this happening? how can I fix it?

gcc版本5.3.0

gcc version 5.3.0

如果有帮助，我会使用vs代码进行编程

I use vs code for programming if it could help

当然我应该适当地包含随机

And of course i properly include random

推荐答案

您正在MinGW上使用std::random_device.更具体地说，您每次需要一个随机数时都在创建一个新实例.不支持此用法(或者不会产生随机数).请参阅为什么对于MinGW具有这种行为的事实，我每次使用mingw gcc4.8.1的std :: random_device运行时都得到相同的顺序吗? >

You are using std::random_device on MinGW. More specifically, you are creating a new instance every time you want a random number. This usage is not supported (or rather, does not produce random numbers). See Why do I get the same sequence for every run with std::random_device with mingw gcc4.8.1? for the fact that MinGW has this behavior, but to fix your particular code, you can do something like this:

std::mt19937_64 rng(std::random_device{}());
std::uniform_int_distribution<int> dist(0, words.size() - 1);

for (int ii = 0; ii < 100; ++ii) {
    std::string curr = words[dist(rng)];
}

也就是说，重复使用同一random_device，而不是一次.如果程序运行之间的随机性很重要，请考虑使用它或使用其他RNG.

That is, use the same random_device repeatedly, rather than just once. And consider seeding it, or using a different RNG, if randomness is important between program runs.

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