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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.
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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。
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。
When executed internally by a `boost::concurrent_flat_map`, the following operations by a user-provided visitation function on the element passed do not introduce data races:
当由 `boost::concurrent_flat_map` 内部执行时，用户提供的访问函数对传入元素执行以下操作不会引入数据竞争：
English Chinese (Simplified Han script) Actions
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。
When executed internally by a `boost::concurrent_flat_map`, the following operations by a user-provided visitation function on the element passed do not introduce data races:
当由 `boost::concurrent_flat_map` 内部执行时，用户提供的访问函数对传入元素执行以下操作不会引入数据竞争：
Read access to the element.
对元素的读取访问。

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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.
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。
06/05/2026
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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.
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.
06/05/2026
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Glossary

English Chinese (Simplified Han script)
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String information

Flags
safe-html, strict-same
Unit identifier
53718
Source string location
:358
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 21