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An allocator whose value type is the same as the table's value type.
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`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
`std::allocator_traits<Alloc>::allocate`
`std::allocator_traits<alloc>::allocate`</alloc>
`std::allocator_traits<Alloc>::deallocate`
`std::allocator_traits<alloc>::deallocate`</alloc>
`std::allocator_traits<Alloc>::construct`
`std::allocator_traits<alloc>::construct`</alloc>
`std::allocator_traits<Alloc>::destroy`
`std::allocator_traits<alloc>::destroy`</alloc>
In general, these requirements on `Hash`, `Pred` and `Allocator` are met if these types are not stateful or if the operations only involve constant access to internal data members.
通常而言，若 `Hash` 、 `Pred` 和 `Allocator` 这些类型不包含状态，或其操作仅涉及对内部数据成员的常量访问，即可满足上述要求。
With the exception of destruction, concurrent invocations of any operation on the same instance of a `concurrent_flat_map` do not introduce data races — that is, they are thread-safe.
除了析构操作外，在同一个 `concurrent_flat_map` 实例上并发调用任何操作都不会引入数据竞争——即这些操作是线程安全的。
If an operation *op* is explicitly designated as _blocking on_ `x`, where `x` is an instance of a `boost::concurrent_flat_map`, prior blocking operations on `x` synchronize with *op*. So, blocking operations on the same `concurrent_flat_map` execute sequentially in a multithreaded scenario.
若某个操作 *op* 被显式指定为__阻塞于__ `x` （其中 `x` 为 `boost::concurrent_flat_map` 实例），则先前对 `x` 的阻塞操作将与 *op* 同步。因此，在多线程场景中，对同一 `concurrent_flat_map` 的阻塞操作将按顺序执行。
English Chinese (Simplified Han script) Actions
value_type(std::piecewise_construct, std::forward_as_tuple(std::forward<K>(k)), std::forward_as_tuple(std::forward<M>(obj))) ```
value_type(std::piecewise_construct, std::forward_as_tuple(std::forward<k>(k)), std::forward_as_tuple(std::forward<m>(obj))) ```</m></k>
Erases the element with key equivalent to `k` if it exists.
若存在键等价于`k`的元素，则删除该元素。
Erases the element `x` with key equivalent to `k` if it exists and `f(x)` is `true`.
若存在键与 `k` 等价的元素 `x`，且 `f(x)` 返回 `true`，则删除该元素。
```c++ template<class ExecutionPolicy, class F> void erase_if(ExecutionPolicy&& policy, F f); ```
```c++ template<class executionpolicy,="" class="" f=""> void erase_if(ExecutionPolicy&amp;&amp; policy, F f); ```</class>
Invokes `f` with non-const references to each of the elements in the table, and erases those for which `f` returns `true`. Execution is parallelized according to the semantics of the execution policy specified.
依次以非常量引用为参数，对容器中的每个元素调用`f`，并删除所有`f`返回`true`的元素。执行过程将根据指定的执行策略语义进行并行化处理。
swap
交换
clear
清空
```c++ void clear() noexcept; ```
```c++ void clear() noexcept; ```
Erases all elements in the table.
清空容器中的所有元素。
Postconditions:;; `size() == 0`, `max_load() >= max_load_factor() * bucket_count()` Concurrency:;; Blocking on `*this`.
后置条件：容器大小 `size() == 0`，且 `max_load() &gt;= max_load_factor() * bucket_count()`
并发：会阻塞当前对象 `*this`。
Returns:;; The number of elements inserted. Concurrency:;; Blocking on `*this` and `source`.
返回值：插入的元素数量。
并发：会阻塞当前对象 `*this` 和源对象 `source`。
Observers
观察器
get_allocator
get_allocator
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。
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
`std::allocator_traits<Alloc>::allocate`
`std::allocator_traits<alloc>::allocate`</alloc>
`std::allocator_traits<Alloc>::deallocate`
`std::allocator_traits<alloc>::deallocate`</alloc>
`std::allocator_traits<Alloc>::construct`
`std::allocator_traits<alloc>::construct`</alloc>
`std::allocator_traits<Alloc>::destroy`
`std::allocator_traits<alloc>::destroy`</alloc>
In general, these requirements on `Hash`, `Pred` and `Allocator` are met if these types are not stateful or if the operations only involve constant access to internal data members.
通常而言，若 `Hash` 、 `Pred` 和 `Allocator` 这些类型不包含状态，或其操作仅涉及对内部数据成员的常量访问，即可满足上述要求。
With the exception of destruction, concurrent invocations of any operation on the same instance of a `concurrent_flat_map` do not introduce data races — that is, they are thread-safe.
除了析构操作外，在同一个 `concurrent_flat_map` 实例上并发调用任何操作都不会引入数据竞争——即这些操作是线程安全的。
If an operation *op* is explicitly designated as _blocking on_ `x`, where `x` is an instance of a `boost::concurrent_flat_map`, prior blocking operations on `x` synchronize with *op*. So, blocking operations on the same `concurrent_flat_map` execute sequentially in a multithreaded scenario.
若某个操作 *op* 被显式指定为__阻塞于__ `x` （其中 `x` 为 `boost::concurrent_flat_map` 实例），则先前对 `x` 的阻塞操作将与 *op* 同步。因此，在多线程场景中，对同一 `concurrent_flat_map` 的阻塞操作将按顺序执行。
An operation is said to be _blocking on rehashing of_ ``__x__`` if it blocks on `x` only when an internal rehashing is issued.
若某个操作仅在触发内部重哈希时才会阻塞于 _`x`_，则称该操作阻塞于 _`x`_ 的重哈希过程。

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Translation uploaded
An allocator whose value type is the same as the table's value type.
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。
06/05/2026
User avatar admin

String added in the repository
An allocator whose value type is the same as the table's value type.
An allocator whose value type is the same as the table's value type.
06/05/2026
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Glossary

English Chinese (Simplified Han script)
No related strings found in the glossary.

String information

Flags
safe-html, strict-same
Unit identifier
53716
Source string location
:344
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 19