en	= Standard Compliance
zh-hans	= 标准符合性

en	:idprefix: compliance_

en	:cpp: C++

en	Closed-addressing Containers
zh-hans	闭寻址容器

en	`boost::unordered_[multi]set` and `boost::unordered_[multi]map` provide a conformant implementation for {cpp}11 (or later) compilers of the latest standard revision of {cpp} unordered associative containers, with very minor deviations as noted. The containers are fully https://en.cppreference.com/w/cpp/named_req/AllocatorAwareContainer[AllocatorAware^] and support https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[fancy pointers^].
zh-hans	`boost::unordered_[multi]set` 和 `boost::unordered_[multi]map` 为支持 {cpp}11 或更高版本的编译器提供了符合最新标准修订版中 {cpp} 无序关联容器规范的实现，仅有极少量的已知偏差。这些容器完全遵循 https://en.cppreference.com/w/cpp/named_req/AllocatorAwareContainer[分配器感知^] ，并支持 https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[花式指针^]。

en	Deduction Guides
zh-hans	推导指引

en	Deduction guides for https://en.cppreference.com/w/cpp/language/class_template_argument_deduction[class template argument deduction (CTAD)^] are only available on {cpp}17 (or later) compilers.
zh-hans	https://en.cppreference.com/w/cpp/language/class_template_argument_deduction[类模板参数推导 (CTAD)] 的推导指南仅在 C{plus}{plus}17（或更高版本）编译器中可用。

en	Piecewise Pair Emplacement
zh-hans	分段式 Pair 就地构造

en	In accordance with the standard specification, `boost::unordered_[multi]map::emplace` supports piecewise pair construction:
zh-hans	根据标准规范， `boost::unordered_[multi]map::emplace` 支持 pair 的分段构造：

en	Additionally, the same functionality is provided via non-standard `boost::unordered::piecewise_construct` and Boost.Tuple:
zh-hans	此外，通过非标准接口 `boost::unordered::piecewise_construct` 与 Boost.Tuple 提供相同功能：

en	This feature has been retained for backwards compatibility with previous versions of Boost.Unordered: users are encouraged to update their code to use `std::piecewise_construct` and ``std::tuple``s instead.
zh-hans	此特性为保持与 Boost.Unordered 旧版本的向后兼容性而保留：建议用户更新代码以使用 `std::piecewise_construct` 与 `std::tuple` 。

en	Swap
zh-hans	交换

en	When swapping, `Pred` and `Hash` are not currently swapped by calling `swap`, their copy constructors are used. As a consequence, when swapping an exception may be thrown from their copy constructor.
zh-hans	执行交换操作时，当前未通过调用 `swap` 函数来交换 `Pred` 和 `Hash` 对象，而是使用其复制构造函数。因此，在交换过程中可能会因其复制构造函数而抛出异常。

en	Open-addressing Containers
zh-hans	开放寻址容器

en	The C++ standard does not currently provide any open-addressing container specification to adhere to, so `boost::unordered_flat_set`/`unordered_node_set` and `boost::unordered_flat_map`/`unordered_node_map` take inspiration from `std::unordered_set` and `std::unordered_map`, respectively, and depart from their interface where convenient or as dictated by their internal data structure, which is radically different from that imposed by the standard (closed addressing).
zh-hans	C++ 标准目前并未提供任何可供遵循的开放定址容器规范，因此 `boost::unordered_flat_set` / `unordered_node_set` 与 `boost::unordered_flat_map` / `unordered_node_map` 分别借鉴 `std::unordered_set` 和 `std::unordered_map` 的设计，并在其内部数据结构（与标准规定的闭寻址方式截然不同）允许或需要时，对接口进行相应调整。

en	Open-addressing containers provided by Boost.Unordered only work with reasonably compliant C++11 (or later) compilers. Language-level features such as move semantics and variadic template parameters are then not emulated. The containers are fully https://en.cppreference.com/w/cpp/named_req/AllocatorAwareContainer[AllocatorAware^] and support https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[fancy pointers^].
zh-hans	Boost.Unordered 提供的开放寻址容器仅兼容符合 C{plus}{plus}1（或更高版本）的编译器，且不再对移动语义、变参模板等语言特性进行模拟实现。这些容器完全符合 https://en.cppreference.com/w/cpp/named_req/AllocatorAwareContainer[分配器感知] 规范，并支持 https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[花式指针] 。

en	The main differences with C++ unordered associative containers are:
zh-hans	与 C{plus}{plus} 无序关联容器的主要区别在于：

en	In general:
zh-hans	总体特性：

en	** `begin()` is not constant-time. ** `erase(iterator)` does not return an iterator to the following element, but a proxy object that converts to that iterator if requested; this avoids a potentially costly iterator increment operation when not needed. ** There is no API for bucket handling (except `bucket_count`). ** The maximum load factor of the container is managed internally and can't be set by the user. The maximum load, exposed through the public function `max_load`, may decrease on erasure under high-load conditions.
zh-hans	** `begin()` 不是常数时间复杂度操作。 ** `erase(iterator)` 不返回指向下一元素的迭代器，而是返回一个代理对象，该对象可按需转换为目标迭代器；这可以避免在无需迭代器时可能产生的高昂递增操作开销。 ** 未提供用于桶管理的 API（除 `bucket_count` 外）。 ** 容器的最大负载因子由内部自动管理，用户无法手动设置。通过公开函数 `max_load` 获取的最大负载值，在高负载情况下执行删除操作时可能会降低。

en	Flat containers (`boost::unordered_flat_set` and `boost::unordered_flat_map`):
zh-hans	扁平容器（ `boost::unordered_flat_set` 与 `boost::unordered_flat_map` ）：

en	** `value_type` must be move-constructible. ** Pointer stability is not kept under rehashing. ** There is no API for node extraction/insertion.
zh-hans	** `value_type` 必须支持移动构造。 ** 在重哈希的过程中，指针稳定性无法保持。 ** 不提供节点提取/插入的 API 接口。

en	Concurrent Containers
zh-hans	并发容器

en	There is currently no specification in the C++ standard for this or any other type of concurrent data structure. The APIs of `boost::concurrent_flat_set`/`boost::concurrent_node_set` and `boost::concurrent_flat_map`/`boost::concurrent_node_map` are modelled after `std::unordered_flat_set` and `std::unordered_flat_map`, respectively, with the crucial difference that iterators are not provided due to their inherent problems in concurrent scenarios (high contention, prone to deadlocking): so, Boost.Unordered concurrent containers are technically not models of https://en.cppreference.com/w/cpp/named_req/Container[Container^], although they meet all the requirements of https://en.cppreference.com/w/cpp/named_req/AllocatorAwareContainer[AllocatorAware^] containers (including https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[fancy pointer^] support) except those implying iterators.
zh-hans	目前 C++ 标准中尚未针对此类或任何其他类型的并发数据结构提供规范。`boost::concurrent_flat_set` / `boost::concurrent_node_set` 与 `boost::concurrent_flat_map` / `boost::concurrent_node_map` 的 API 分别参照 `std::unordered_flat_set` 和 `std::unordered_flat_map` 设计，但有一个关键区别：由于迭代器在并发场景中存在的固有问题（高竞争、易死锁），这些容器不提供迭代器。因此，Boost.Unordered 并发容器在技术上并不符合 https://en.cppreference.com/w/cpp/named_req/Container[容器^] 的模型，但它们满足 https://en.cppreference.com/w/cpp/named_req/AllocatorAwareContainer[分配器感知^] 容器（包括 https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[花式指针^] 支持）中除涉及迭代器之外的所有要求。

en	In a non-concurrent unordered container, iterators serve two main purposes:
zh-hans	在非并发无序容器中，迭代器主要有两项核心功能：

en	Access to an element previously located via lookup.
zh-hans	访问先前通过查找定位的元素。

en	Container traversal.
zh-hans	容器遍历。

en	In place of iterators, Boost.Unordered concurrent containers use _internal visitation_ facilities as a thread-safe substitute. Classical operations returning an iterator to an element already existing in the container, like for instance:
zh-hans	为替代迭代器，Boost.Unordered 并发容器使用__内部访问__机制作为线程安全的替代方案。传统操作会返回指向容器中既有元素的迭代器（例如下列）：

en	are transformed to accept a _visitation function_ that is passed such element:
zh-hans	被改造为接受传递该元素的__访问函数__：

en	(In the second case `f` is only invoked if there's an equivalent element to `obj` in the table, not if insertion is successful). Container traversal is served by:
zh-hans	（第二种情况中，仅当表中存在与 `obj` 等价元素时才会调用 `f` ，而非在插入成功时调用）。容器遍历通过以下方式实现：

en	of which there are parallelized versions in C++17 compilers with parallel algorithm support. In general, the interface of concurrent containers is derived from that of their non-concurrent counterparts by a fairly straightforward process of replacing iterators with visitation where applicable. If for regular maps `iterator` and `const_iterator` provide mutable and const access to elements, respectively, here visitation is granted mutable or const access depending on the constness of the member function used (there are also `*cvisit` overloads for explicit const visitation); In the case of `boost::concurrent_flat_set`, visitation is always const.
zh-hans	在支持并行算法的 C{plus}{plus}17 编译器中提供并行化版本。通常，并发容器的接口通过将迭代器替换为访问机制的过程从非并发版本派生。对于常规映射， `iterator` 和 `const_iterator` 分别提供对元素的非常量和常量访问；此处访问权限取决于所用成员函数的常量性（同时提供 `*cvisit` 重载用于显式常量访问）。对于 `boost::concurrent_flat_set` ，访问操作始终为常量。

en	One notable operation not provided by `boost::concurrent_flat_map`/`boost::concurrent_node_map` is `operator[]`/`at`, which can be replaced, if in a more convoluted manner, by `xref:reference/concurrent_flat_map.adoc#concurrent_flat_map_try_emplace_or_cvisit[try_emplace_or_visit]`.
zh-hans	`boost::concurrent_flat_map` / `boost::concurrent_node_map` 未提供的一个关键操作是 `operator[]` / `at` ，该功能可通过 xref:reference/concurrent_flat_map.adoc#concurrent_flat_map_try_emplace_or_cvisit[`try_emplace_or_visit`] 实现替代（该方式更为复杂）。