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Constructs an empty table using `hasher()` as the hash function, `key_equal()` as the key equality predicate and `allocator_type()` as the allocator.
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Visitation functions executed by a `boost::concurrent_flat_map` `x` are not allowed to invoke any operation on `x`; invoking operations on a different `boost::concurrent_flat_map` instance `y` is allowed only if concurrent outstanding operations on `y` do not access `x` directly or indirectly.
由 `boost::concurrent_flat_map` 容器 `x` 执行的访问函数不得调用 `x` 上的任何操作；仅当对另一 `boost::concurrent_flat_map` 实例 `y` 的并发的未完成操作不直接或间接访问 `x` 时，才允许调用实例 `y` 上的操作。
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Configuration Macros
配置宏
`BOOST_UNORDERED_DISABLE_REENTRANCY_CHECK`
`BOOST_UNORDERED_DISABLE_REENTRANCY_CHECK`
In debug builds (more precisely, when link:../../../../../assert/doc/html/assert.html#boost_assert_is_void[`BOOST_ASSERT_IS_VOID`^] is not defined), __container reentrancies__ (illegaly invoking an operation on `m` from within a function visiting elements of `m`) are detected and signalled through `BOOST_ASSERT_MSG`. When run-time speed is a concern, the feature can be disabled by globally defining this macro.
在调试版本中（更准确地说，当未定义 link:../../../../../assert/doc/html/assert.html#boost_assert_is_void[`BOOST_ASSERT_IS_VOID`] 时），系统会检测__容器重入__行为（即在访问 `m` 元素的函数内部非法调用 `m` 上的操作），并通过 `BOOST_ASSERT_MSG` 发出信号。若需关注运行时速度，可通过全局定义此宏来禁用该功能。
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`BOOST_UNORDERED_ENABLE_STATS`
`BOOST_UNORDERED_ENABLE_STATS`
Globally define this macro to enable xref:reference/stats.adoc#stats[statistics calculation] for the table. Note that this option decreases the overall performance of many operations.
全局定义此宏以启用容器的 xref:reference/stats.adoc#stats[统计计算] 功能。请注意，此选项会降低多数操作的总体性能。
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Constants
常量
```cpp static constexpr size_type bulk_visit_size; ```
```cpp static constexpr size_type bulk_visit_size; ```
Chunk size internally used in xref:concurrent_flat_map_bulk_visit[bulk visit] operations.
xref:concurrent_flat_map_bulk_visit [批量访问] 操作内部使用的块大小。
Constructors
构造函数
Default Constructor
默认构造函数
```c++ concurrent_flat_map(); ```
```c++ concurrent_flat_map(); ```
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。
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Postconditions:;; `size() == 0` Requires:;; If the defaults are used, `hasher`, `key_equal` and `allocator_type` need to be https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[DefaultConstructible^].
后置条件：size() == 0
要求：若使用默认构造方式，则hasher、key_equal和allocator_type必须满足https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[默认可构造]要求。
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Bucket Count Constructor
桶数构造函数
```c++ explicit concurrent_flat_map(size_type n, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type()); ```
```c++ explicit concurrent_flat_map(size_type n, const hasher& hf = hasher(), const key_equal& eql = key_equal(), const allocator_type& a = allocator_type()); ```
Constructs an empty table with at least `n` buckets, using `hf` as the hash function, `eql` as the key equality predicate, and `a` as the allocator.
构造一个至少包含n个桶的空表，使用hf作为哈希函数、eql作为键相等谓词、a作为分配器。
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Postconditions:;; `size() == 0` Requires:;; If the defaults are used, `hasher`, `key_equal` and `allocator_type` need to be https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[DefaultConstructible^].
后置条件：size() == 0
要求：若使用默认参数，则hasher、key_equal和allocator_type必须满足https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[默认可构造]要求。
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Iterator Range Constructor
迭代器范围构造函数
Constructs an empty table with at least `n` buckets, using `hf` as the hash function, `eql` as the key equality predicate and `a` as the allocator, and inserts the elements from `[f, l)` into it.
构造一个至少包含 `n` 个桶的空容器，使用 `hf` 作为哈希函数、 `eql` 作为键相等性谓词、 `a` 作为分配器，并将 `[f, l)` 范围内的元素插入其中。
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Requires:;; If the defaults are used, `hasher`, `key_equal` and `allocator_type` need to be https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[DefaultConstructible^].
要求;; 若使用默认值，则 `hasher` 、 `key++_++equal` 和 `allocator++_++type` 需满足 https://en.cppreference.com/w/cpp/named_req/DefaultConstructible[可默认构造] 要求。
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Copy Constructor
复制构造函数
```c++ concurrent_flat_map(concurrent_flat_map const& other); ```
```c++ concurrent_flat_map(concurrent_flat_map const& other); ```
The copy constructor. Copies the contained elements, hash function, predicate and allocator.
拷贝构造函数。复制容器内的元素、哈希函数、谓词以及分配器。
If `Allocator::select_on_container_copy_construction` exists and has the right signature, the allocator will be constructed from its result.
若Allocator::select_on_container_copy_construction存在且签名正确，则分配器将根据其返回值构造。
English Chinese (Simplified Han script) Actions
```c++ void rehash(size_type n); ```
```c++ void rehash(size_type n); ```
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; ```

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Constructs an empty table using `hasher()` as the hash function, `key_equal()` as the key equality predicate and `allocator_type()` as the allocator.
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。
06/05/2026
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Constructs an empty table using `hasher()` as the hash function, `key_equal()` as the key equality predicate and `allocator_type()` as the allocator.
Constructs an empty table using `hasher()` as the hash function, `key_equal()` as the key equality predicate and `allocator_type()` as the allocator.
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
53754
Source string location
:452
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 57