是std :: map和std :: vector线程安全吗？ [英] Are std::map and std::vector thread safe?

问题描述

我正在开发一个多线程应用程序，每个线程将从一组映射和向量中读取（将不会修改结构）。任何人都可以告诉，因为线程只是从这些结构读取，有必要在这些结构被读取的代码块周围实现一个可共享互斥体？

I am developing a multi threaded application, each thread will read (there will be no modifying of structures) from a group of maps and vectors. Can anyone please advise, since the threads are only reading from these structures would it be necessary to implement a sharable mutex around the code blocks where these structures are being read?

推荐答案

在只读映射/向量的情况下，不需要使用互斥体。
这已经回答了向量和地图

虽然C ++ 03 doesn

In case of read only map/vector there is no need to use mutexes. This was already answered for both vector and map
While C++03 doesn't mention threads, C++11 has clause covering you question.

1为了避免数据竞争（17.6.5.9），实现应考虑以下函数为
const：begin，end，rbegin，rend，前缀，后面，数据，查找，下限，上限，等于，在
和除了在关联或无序的关联容器中，operator []。

2尽管（17.6.5.9）当包含
对象的同一序列中不同元素中的内容除了向量< bool> 时，需要避免数据竞争。
3 [注意：对于大小大于1的向量< int> x，x [1] = 5和* x.begin（）= 10可以在没有数据竞争的情况下同时执行
，但是x [0] = 5和* x.begin（）= 10同时执行可能导致
a数据竞争。作为一般规则的例外， bool> y，y [0] = true可能与y [1]竞争
= true。 -end note]

1 For purposes of avoiding data races (17.6.5.9), implementations shall consider the following functions to be const: begin, end, rbegin, rend, front, back, data, find, lower_bound, upper_bound, equal_range, at and, except in associative or unordered associative containers, operator[].
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.
3 [ Note: For a vector<int> x with a size greater than one, x[1] = 5 and *x.begin() = 10 can be executed concurrently without a data race, but x[0] = 5 and *x.begin() = 10 executed concurrently may result in a data race. As an exception to the general rule, for a vector < bool > y, y[0] = true may race with y[1] = true. —end note ]

因此，在C ++ 11中，不仅允许读取对象，对象（但不是容器！）， bool>

Thus in C++11 it is allowed not only to read objects , but also allow concurrent modification of its different objects(but not container!), with exception for vector < bool >

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