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`std::pair<const Key, T>` must be https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[EmplaceConstructible^] into the table from any `std::pair` object convertible to it, and it also must be https://en.cppreference.com/w/cpp/named_req/Erasable[Erasable^] from the table.
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[#concurrent_flat_map]
[#concurrent_flat_map]
Class Template concurrent_flat_map
类模板 concurrent_flat_map
:idprefix: concurrent_flat_map_
:idprefix: concurrent_flat_map_
`boost::concurrent_flat_map` — A hash table that associates unique keys with another value and allows for concurrent element insertion, erasure, lookup and access without external synchronization mechanisms.
`boost::concurrent_flat_map` — 一种哈希表，将唯一键与对应值关联，并允许在无需外部同步机制的情况下进行并发的元素插入、删除、查找和访问。
Even though it acts as a container, `boost::concurrent_flat_map` does not model the standard C++ https://en.cppreference.com/w/cpp/named_req/Container[Container^] concept. In particular, iterators and associated operations (`begin`, `end`, etc.) are not provided. Element access and modification are done through user-provided _visitation functions_ that are passed to `concurrent_flat_map` operations where they are executed internally in a controlled fashion. Such visitation-based API allows for low-contention concurrent usage scenarios.
尽管它充当容器的角色，boost::concurrent_flat_map 并未遵循标准 C++ 的 https://en.cppreference.com/w/cpp/named_req/Container[Container^] 概念。特别地，它不提供迭代器及相关操作（例如 begin、end 等）。元素的访问和修改是通过用户提供的 访问函数 来完成的，这些函数被传递给 concurrent_flat_map 的操作，并以受控的方式在内部执行。这种基于访问的 API 能够实现低竞争并发的使用场景。
The internal data structure of `boost::concurrent_flat_map` is similar to that of `boost::unordered_flat_map`. As a result of its using open-addressing techniques, `value_type` must be move-constructible and pointer stability is not kept under rehashing.
`boost::concurrent++_++flat++_++map` 的内部数据结构与 `boost::unordered++_++flat++_++map` 类似。由于采用开放寻址技术， `value++_++type` 必须支持移动构造，且在重哈希过程中无法保持指针稳定性。
Synopsis
概要
:329
---
---
Description
描述
*Template Parameters*
*模板参数*
_Key_
_键_
`std::pair<const Key, T>` must be https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[EmplaceConstructible^] into the table from any `std::pair` object convertible to it, and it also must be https://en.cppreference.com/w/cpp/named_req/Erasable[Erasable^] from the table.
`std::pair<const key,="" t="">` 必须能够从任何可转换为其的 `std::pair` 对象出发，在表中进行 https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[EmplaceConstructible^] 构造，并且也必须可以从表中进行 https://en.cppreference.com/w/cpp/named_req/Erasable[Erasable^] 擦除。</const>
_T_
_T_
_Hash_
_Hash_
A unary function object type that acts a hash function for a `Key`. It takes a single argument of type `Key` and returns a value of type `std::size_t`.
一种一元函数对象类型，用作Key类型的哈希函数。它接受单个Key类型的参数，并返回std::size_t类型的值。
_Pred_
_Pred_
A binary function object that induces an equivalence relation on values of type `Key`. It takes two arguments of type `Key` and returns a value of type `bool`.
一种二元函数对象，用于在Key类型的值上引入等价关系。该对象接收两个Key类型的参数，并返回一个bool类型的值。
_Allocator_
_Allocator_
An allocator whose value type is the same as the table's value type.
值类型与哈希表值类型相同的分配器。
Allocators using https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[fancy pointers] are supported.
支持使用https://en.cppreference.com/w/cpp/named_req/Allocator#Fancy_pointers[花式指针] 的分配器。
The elements of the table are held into an internal _bucket array_. An element is inserted into a bucket determined by its hash code, but if the bucket is already occupied (a _collision_), an available one in the vicinity of the original position is used.
容器的元素存储在内部的__桶数组__中。元素根据其哈希码被插入到对应的桶中，但如果该桶已被占用（即发生__冲突__），则会使用原始位置附近可用的桶。
The size of the bucket array can be automatically increased by a call to `insert`/`emplace`, or as a result of calling `rehash`/`reserve`. The _load factor_ of the table (number of elements divided by number of buckets) is never greater than `max_load_factor()`, except possibly for small sizes where the implementation may decide to allow for higher loads.
桶数组的大小可通过调用 `insert` / `emplace` 自动增加，也可通过调用 `rehash` / `reserve` 进行调整。容器的__负载因子__（元素数量与桶数量的比值）永远不会超过 `max++_++load++_++factor()` ，但在小规模数据情况下，实现可能允许更高的负载因子。
If `link:../../../../../container_hash/doc/html/hash.html#ref_hash_is_avalanchinghash[hash_is_avalanching]<Hash>::value` is `true`, the hash function is used as-is; otherwise, a bit-mixing post-processing stage is added to increase the quality of hashing at the expense of extra computational cost.
若 link:../../../../../container_hash/doc/html/hash.html#ref_hash_is_avalanchinghash[`hash++_++is++_++avalanching`]`++&lt;++Hash++&gt;++::value` 为 `true` ，则直接使用哈希函数；否则，会添加一个位混合后处理阶段以提高哈希质量，但会牺牲额外的计算成本。
:371
---
---
Concurrency Requirements and Guarantees
并发要求与保证
Concurrent invocations of `operator()` on the same const instance of `Hash` or `Pred` are required to not introduce data races. For `Alloc` being either `Allocator` or any allocator type rebound from `Allocator`, concurrent invocations of the following operations on the same instance `al` of `Alloc` are required to not introduce data races:
要求对同一 `Hash` 或 `Pred` 常量实例并发调用 `operator()` 时不得引入数据竞争。对于 `Alloc` （即 `Allocator` 或其重绑定后的任意分配器类型），在同一实例 `al` 上并发调用以下操作时不得引入数据竞争：
Copy construction from `al` of an allocator rebound from `Alloc`
从Alloc重新绑定后的分配器的al进行拷贝构造
English Chinese (Simplified Han script) Actions
Throws:;; The function has no effect if an exception is thrown, unless it is thrown by the table's hash function or comparison function. Concurrency:;; Blocking on `*this`.
异常：若抛出异常，函数无任何效果（由容器的哈希函数或比较函数抛出的异常除外）。
并发：阻塞当前对象 `*this`。
Statistics
统计信息
reset_stats
reset_stats
```c++ void reset_stats() noexcept; ```
```c++ void reset_stats() noexcept; ```
Effects:;; Sets to zero the internal statistics kept by the table. Notes:;; Only available if xref:reference/stats.adoc#stats[statistics calculation] is xref:concurrent_flat_map_boost_unordered_enable_stats[enabled].
效果：将容器维护的内部统计数据归零。
说明：仅当**启用统计计算**时，该函数才可用。
__iter-value-type__
_iter-value-type_
Class Template concurrent_flat_map
类模板 concurrent_flat_map
:idprefix: concurrent_flat_map_
:idprefix: concurrent_flat_map_
`boost::concurrent_flat_map` — A hash table that associates unique keys with another value and allows for concurrent element insertion, erasure, lookup and access without external synchronization mechanisms.
`boost::concurrent_flat_map` — 一种哈希表，将唯一键与对应值关联，并允许在无需外部同步机制的情况下进行并发的元素插入、删除、查找和访问。
Even though it acts as a container, `boost::concurrent_flat_map` does not model the standard C++ https://en.cppreference.com/w/cpp/named_req/Container[Container^] concept. In particular, iterators and associated operations (`begin`, `end`, etc.) are not provided. Element access and modification are done through user-provided _visitation functions_ that are passed to `concurrent_flat_map` operations where they are executed internally in a controlled fashion. Such visitation-based API allows for low-contention concurrent usage scenarios.
尽管它充当容器的角色，boost::concurrent_flat_map 并未遵循标准 C++ 的 https://en.cppreference.com/w/cpp/named_req/Container[Container^] 概念。特别地，它不提供迭代器及相关操作（例如 begin、end 等）。元素的访问和修改是通过用户提供的 访问函数 来完成的，这些函数被传递给 concurrent_flat_map 的操作，并以受控的方式在内部执行。这种基于访问的 API 能够实现低竞争并发的使用场景。
The internal data structure of `boost::concurrent_flat_map` is similar to that of `boost::unordered_flat_map`. As a result of its using open-addressing techniques, `value_type` must be move-constructible and pointer stability is not kept under rehashing.
`boost::concurrent++_++flat++_++map` 的内部数据结构与 `boost::unordered++_++flat++_++map` 类似。由于采用开放寻址技术， `value++_++type` 必须支持移动构造，且在重哈希过程中无法保持指针稳定性。
*Template Parameters*
*模板参数*
_Key_
_键_
Concurrency Requirements and Guarantees
并发要求与保证
Constructs an empty table using `hasher()` as the hash function, `key_equal()` as the key equality predicate and `allocator_type()` as the allocator.
使用hasher()作为哈希函数、key_equal()作为键相等谓词、allocator_type()作为分配器，构造一个空表。
`std::pair<const Key, T>` must be https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[EmplaceConstructible^] into the table from any `std::pair` object convertible to it, and it also must be https://en.cppreference.com/w/cpp/named_req/Erasable[Erasable^] from the table.
`std::pair<const key,="" t="">` 必须能够从任何可转换为其的 `std::pair` 对象出发，在表中进行 https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[EmplaceConstructible^] 构造，并且也必须可以从表中进行 https://en.cppreference.com/w/cpp/named_req/Erasable[Erasable^] 擦除。</const>
[#concurrent_flat_map]
[#concurrent_flat_map]
_Hash_
_Hash_
Requires:;; `value_type` is copy constructible Concurrency:;; Blocking on `other`.
要求：value_type 支持复制构造。 并发特性：阻塞于 other
Complexity:;; O(`bucket_count()`)
复杂度：O (`bucket_count()`)
Move Assignment
移动赋值
A unary function object type that acts a hash function for a `Key`. It takes a single argument of type `Key` and returns a value of type `std::size_t`.
一种一元函数对象类型，用作Key类型的哈希函数。它接受单个Key类型的参数，并返回std::size_t类型的值。
_Pred_
_Pred_
Non-mutable modification of the element.
对元素的非可变修改。
```c++ concurrent_flat_map(concurrent_flat_map&& other, Allocator const& a); ```
```c++ concurrent_flat_map(concurrent_flat_map&amp;&amp; other, Allocator const&amp; a); ```
reserve
保留
Mutable modification of the element:
对元素的可变修改：
```c++ [[nodiscard]] bool empty() const noexcept; ```
```c++ [[nodiscard]] bool empty() const noexcept; ```
```c++ size_type size() const noexcept; ```
```c++ size_type size() const noexcept; ```
Returns:;; The number of elements in the table.
返回值：表中的元素数量。

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`std::pair<const Key, T>` must be https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[EmplaceConstructible^] into the table from any `std::pair` object convertible to it, and it also must be https://en.cppreference.com/w/cpp/named_req/Erasable[Erasable^] from the table.
`std::pair<const Key, T>` must bekey,="" t="">` 必须能够从任何可转换为其的 `std::pair` 对象出发，在表中进行 https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[EmplaceConstructible^] into the table from any `std::pair` object convertible to it, and it also must be构造，并且也必须可以从表中进行 https://en.cppreference.com/w/cpp/named_req/Erasable[Erasable^] from the table.擦除。</const>
06/05/2026
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`std::pair<const Key, T>` must be https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[EmplaceConstructible^] into the table from any `std::pair` object convertible to it, and it also must be https://en.cppreference.com/w/cpp/named_req/Erasable[Erasable^] from the table.
`std::pair<const Key, T>` must be https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[EmplaceConstructible^] into the table from any `std::pair` object convertible to it, and it also must be https://en.cppreference.com/w/cpp/named_req/Erasable[Erasable^] from the table.
06/05/2026
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Flags
safe-html, strict-same
Unit identifier
53709
Source string location
:340
String age
06/05/2026
Last updated
06/06/2026
Source string age
06/05/2026
Translation file AsciiDoc file
doc/modules/ROOT/pages/reference/concurrent_flat_map_zh_Hans.adoc, string 12