C ++ std :: atomic与Boost原子 [英] C++ std::atomic vs. Boost atomic

问题描述

在我的应用程序中，我有一个int和一个bool变量，被多个线程访问（多个写/读）。目前，我使用两个互斥体，一个为int，一个为bool保护这些变量。

In my application, I have an int and a bool variable, which are accessed (multiple write/read) by multiple threads. Currently, I am using two mutexes, one for int and one for bool to protect those variables.

我听说过使用原子变量和操作符来写锁，线程程序。我的问题是

I heard about using atomic variables and operators to write lock-free multi-thread program. My questions are

1. 原子变量和运算符的定义是什么？


2. std :: atomic 和
   boost / atomic.hpp ？哪一个更标准或更流行？


3. 这些库是平台相关的吗？我现在使用gnu gcc 4.6 on
   Linux，但理想情况下它应该是跨平台的。我听说原子的定义实际上还取决于硬件。任何人都可以解释一下吗？


4. 在多个线程之间共享bool变量的最好方法是什么？我不想使用 volatile 关键字。

1. What's the definition of atomic variables and operators?
2. What's the main difference between std::atomic and boost/atomic.hpp? Which one is more standard or popular?
3. Are these libraries platform-dependent? I am using gnu gcc 4.6 on Linux at the moment, but ideally it shall be cross-platform. I heard that the definition of "atomic" actually depends on the hardware as well. Can anyone explain that as well?
4. What's the best way to share a bool variable among multiple threads? I would prefer not to use the "volatile" keyword.

这些代码是否线程安全？ / p>

Are these code thread-safe?

double double_m; // double_m is only accessed by current thread.
std::atomic<bool> atomic_bool_x;
atomic_bool_x = true && (double_m > 12.5);

int int_n; // int_n is only accessed by current thread.
std::atomic<int> atomic_int_x;
std::atomic<int> atomic_int_y;
atomic_int_y = atomic_int_x * int_n;

推荐答案

我不是专家或任何东西，我知道：

I'm not an expert or anything, but here's what I know:

1. std :: atomic $ c> load 和 store （以及一些其他操作）是明确定义的。


2. 我假设 std :: atomic 是基于 boost :: atomic 。如果可以，使用 std ，否则使用 boost 。


3. 两个可移植的， std 完全是这样，但是你的编译器将需要支持C ++ 11


4. 可能 std :: atomic_bool 。您不应该使用volatile。

1. std::atomic simply says that calling load and store (and a few other operations) concurrently is well-defined. An atomic operation is indivisible - nothing can happen 'in-between'.
2. I assume std::atomic is based off of boost::atomic. If you can, use std, otherwise use boost.
3. They are both portable, with the std being completely so, however your compiler will need to support C++11
4. Likely std::atomic_bool. You should not need to use volatile.

此外，我相信 load store 不同于 operator = / operator T 只有加载 / 存储是原子。

Also, I believe load/store differs from operator=/operator T only load/store are atomic.

不要迷茫。我检查了标准，看起来操作符是以 load / store / etc定义的，但是他们可能返回不同的东西。

Nevermind. I checked the standard and it appears that the operators are defined in terms of load/store/etc, however they may return different things.

进一步阅读：

• http://en.cppreference.com/w/cpp/atomic/atomic


• C ++ 11标准


• C ++并行操作

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