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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_node_map]
[#concurrent_node_map]
Class Template concurrent_node_map
类模板 concurrent++_++node++_++map
:idprefix: concurrent_node_map_
:idprefix: concurrent_node_map_
`boost::concurrent_node_map` — A node-based 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++_++node++_++map` —— 一种基于节点的哈希表，用于建立唯一键与对应值的关联，并支持在无外部同步机制的情况下并发执行元素插入、擦除、查找和访问操作。
Even though it acts as a container, `boost::concurrent_node_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_node_map` operations where they are executed internally in a controlled fashion. Such visitation-based API allows for low-contention concurrent usage scenarios.
尽管 `boost::concurrent++_++node++_++map` 的行为类似于容器，但它并不符合标准 C{plus}{plus} 的 https://en.cppreference.com/w/cpp/named_req/Container[容器] 概念模型。具体而言，它不提供迭代器及相关操作（如 `begin` 、 `end` 等）。元素的访问和修改通过用户提供的__访问函数__来实现，这些函数被传递至 `concurrent++_++node++_++map` 的操作中，并在其内部以受控方式执行。这种基于访问的 API 设计能够支持低争用的并发应用场景。
The internal data structure of `boost::concurrent_node_map` is similar to that of `boost::unordered_node_map`. Unlike `boost::concurrent_flat_map`, pointer stability and node handling functionalities are provided, at the expense of potentially lower performance.
`boost::concurrent++_++node++_++map` 的内部数据结构与 `boost::unordered++_++node++_++map` 类似。与 `boost::concurrent++_++flat++_++map` 不同，它提供了指针稳定性和节点处理功能，但代价是可能带来性能上的损失。
Synopsis
概要
:347
---
---
Description
描述
*Template Parameters*
*模板参数*
_Key_
_键_
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` 对象 https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[原地构造] 到容器中，并且必须支持从容器中 https://en.cppreference.com/w/cpp/named_req/Erasable[擦除] 。
_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`.
一元函数对象类型，用作 `Key` 的哈希函数。它接受一个类型为 `Key`
_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，用于对Key类型的值建立等价关系。它接受两个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.
值类型与该表的值类型一致的分配器。
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 element nodes of the table are held into an internal _bucket array_. An node is inserted into a bucket determined by the hash code of its element, but if the bucket is already occupied (a _collision_), an available one in the vicinity of the original position is used.
哈希表的元素节点存储在内部**桶数组**中。节点会根据其元素的哈希值插入到对应的桶中；若该桶已被占用（即发生**哈希冲突**），则使用原位置附近的可用桶。
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.
通过调用 `insert`/`emplace`，或执行 `rehash`/`reserve` 操作，可自动增大桶数组的大小。哈希表的**负载因子**（元素数量除以桶数量）永远不会大于 `max_load_factor()`，仅在尺寸极小时，实现可能允许更高的负载。
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]<hash>::value` 为 `true`，则直接使用原哈希函数；否则会添加一个比特混合后处理阶段，以额外计算开销为代价提升哈希质量。</hash>
:388
---
---
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 `al` 复制构造重新绑定的分配器
English Chinese (Simplified Han script) Actions
get_allocator
get++_++allocator
``` allocator_type get_allocator() const noexcept; ```
``` allocator_type get_allocator() const noexcept; ```
Returns:;; The table's allocator.
返回值：;; 表的分配器。
hash_function
哈希函数
``` hasher hash_function() const; ```
``` hasher hash_function() const; ```
Returns:;; The table's hash function.
返回值：;; 表的哈希函数。
``` key_equal key_eq() const; ```
``` key_equal key_eq() const; ```
Returns:;; The table's key equality predicate.
返回值：;; 表的键相等性谓词。
contains
包含
```c++ bool contains(const key_type& k) const; template<class K> bool contains(const K& k) const; ```
```c++ bool contains(const key_type&amp; k) const; template<class k=""> bool contains(const K&amp; k) const; ```</class>
Bucket Interface
桶接口
bucket_count
bucket_count
```c++ size_type bucket_count() const noexcept; ```
```c++ size_type bucket_count() const noexcept; ```
Returns:;; The size of the bucket array.
返回值：;; 桶数组的大小。
max_load_factor
max_load_factor（最大负载因子）
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` 对象 https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[原地构造] 到容器中，并且必须支持从容器中 https://en.cppreference.com/w/cpp/named_req/Erasable[擦除] 。
```c++ float max_load_factor() const noexcept; ```
```c++ float max_load_factor() const noexcept; ```
Constructors
构造函数
When `size() == 0`, `rehash(0)` will deallocate the underlying buckets array.
效果：;; 当容器元素数量 `size() == 0` 时，调用 `rehash(0)` 会释放底层桶数组的内存。
Allocator Constructor
分配器构造函数
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`. ---
抛出异常：;; 若抛出异常，函数不会产生任何效果（由容器的哈希函数或比较函数抛出的异常除外）。
并发特性：;; 阻塞当前容器 `*this`。
reserve
保留
Returns:;; A statistical description of the insertion and lookup operations performed by the table so far. Notes:;; Only available if xref:reference/stats.adoc#stats[statistics calculation] is xref:concurrent_node_map_boost_unordered_enable_stats[enabled].
返回值：;; 表截至目前执行的插入和查找操作的统计信息描述。
注意：;; 仅当启用了**统计信息计算**功能时可用。
reset_stats
reset_stats
```c++ void reset_stats() noexcept; ```
```c++ void reset_stats() noexcept; ```
Move construction from a xref:#unordered_node_map[`unordered_node_map`]. The internal bucket array of `other` is transferred directly to the new container. The hash function, predicate and allocator are moved-constructed from `other`. If statistics are xref:concurrent_node_map_boost_unordered_enable_stats[enabled], transfers the internal statistical information from `other` and calls `other.reset_stats()`.
通过 xref:#unordered_node_map[`unordered_node_map`] 进行移动构造。将 `other` 的内部桶数组直接转移到新容器中。哈希函数、谓词和分配器均从 `other` 移动构造而来。若启用了 xref:concurrent_node_map_boost_unordered_enable_stats[统计功能]，则从 `other` 转移内部统计信息，并调用 `other.reset_stats()`。
__iter-key-type__
__iter-key-type__
__iter-mapped-type__
__iter-mapped-type__
__iter-to-alloc-type__
__iter-to-alloc-type__
Equality Comparisons
相等性比较

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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.
into the table from any `std::pair` object convertible to it, and it also must be`std::pair` 对象 https://en.cppreference.com/w/cpp/named_req/EmplaceConstructible[原地构造] 到容器中，并且必须支持从容器中 https://en.cppreference.com/w/cpp/named_req/Erasable[Erasable^] from the table.擦除] 。
06/05/2026
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String added in the repository
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.
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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Glossary

English Chinese (Simplified Han script)
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String information

Flags
safe-html, strict-same
Unit identifier
51764
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_node_map_zh_Hans.adoc, string 12