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如果线程在不相交的索引范围内读写，则std :: vector线程安全吗？

[英]Is a std::vector threadsafe if the threads read and write in disjoint index ranges?

原文 2016-08-26 09:56:42 0 1 c++/ thread-safety/ stdvector

Suppose, I have a std::vector<int> of length 4, which is constant. 假设我有一个长度为4的std::vector<int> ，它是恒定的。 Then there are 4 threads, where thread i reads and writes only index i . 然后有4个线程，其中线程i只能读写索引i 。 Is this threadsafe? 这是线程安全的吗？ Can the single elements be changed independently of each other? 单个元素可以相互独立更改吗？ I wonder because they are close so that they are probably loaded all at once into a cacheline. 我想知道，因为它们很近，因此可能一次将它们全部加载到缓存行中。

Does it make a difference if the index range per thread is larger than 1? 如果每个线程的索引范围大于1，是否会有所不同？

EDIT: 编辑：

I am using Visual Studio 2010 and hence C++03. 我正在使用Visual Studio 2010，因此使用的是C ++ 03。 Any hints about differences from C++03 to C++11 are welcome! 任何有关从C ++ 03到C ++ 11的差异的提示都欢迎！

1 个解决方案

Yes that's fine. 是的，没关系。 Different threads can operate on different ranges of elements. 不同的线程可以在不同范围的元素上运行。

According to the C++11 Standard: 根据C++11标准：

23.2.2 Container data races [container.requirements.dataraces] 23.2.2容器数据竞赛[container.requirements.dataraces]

2 Notwithstanding (17.6.5.9), implementations are required to avoid data races when the contents of the contained object in different elements in the same sequence, excepting vector<bool>, are modified concurrently. 2尽管有（17.6.5.9），当同时修改了相同对象（除了vector <bool>）中不同元素中包含的对象的内容时，仍需要实现以避免数据争用。

Edit: Before C++11 concurrency and data races are never mentioned, so the spec took no account of them and made no guarantees. 编辑：从来没有提到C++11并发性和数据争用，因此规范没有考虑它们，也没有做出任何保证。