问题描述
我有一个函数需要执行 n=1000 次.这个函数进行蒙特卡罗风格的模拟并返回一个 int 作为结果.我想并行运行 nthreads=4.每当一个线程完成一个循环时，它应该将结果放入std::vector.因此，在 1000 个周期后，我有一个可以通过统计检查的 1000 个 int 向量.
I'm having a function that needs to be executed n=1000 times. This functions does a Monte Carlo style simulation and returns an int as the result. I'd like to run nthreads=4 in parallel. Whenever a thread finishes one cycle, it should put the result in a std::vector<int>.
Thus, after 1000 cycles, I've a vector of 1000 ints that can be examined by statistics.
由于 std::vector 不是线程安全的，我想到了 std::mutex(这肯定会工作).
Since a std::vector is not thread-safe, I thought about std::mutex (which would surely work).
但是我想知道是否可以将向量声明为原子向量从而绕过互斥锁?是否可以有 std::atomic?我可以在上面使用 push_back 等吗?
But I wonder if I can declare a vector to be atomic and thus get around mutexes?
Is it possible to have a std::atomic<std::vector<int>>? And can I use push_back etc. on it?
推荐答案
你不需要.从多个线程访问 std::vector 是完全可以的，if
You don't need to. It is totally okay to access a std::vector from multiple threads, if
- 你读取对象
- 你写给不同的对象
因此，请确保创建一个大小为 n=1000 的向量，并根据您的线程编号(1 到 4)将元素 0-249、250-499 等分配给您的线程.
So just make sure, you create a vector of size n=1000 and depending on your thread number (1 to 4) you assign elements 0-249, 250-499 etc. to your threads.
所以你的每个线程都会计算 n/nthreads 个元素.
So each of your thread computes n/nthreads elements.
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