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Returns:;; `size() == 0`
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Throws:;; Depending on the exception handling mechanism of the execution policy used, may call `std::terminate` if an exception is thrown within `f`. Notes:;; Only available in compilers supporting C++17 parallel algorithms. + + These overloads only participate in overload resolution if `std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>` is `true`. + + Unsequenced execution policies are not allowed.
抛出异常：;; 依据所使用执行策略的异常处理机制，若 `f` 内部抛出异常，则可能调用 `std::terminate`。
注意：;; 仅在支持 C++17 并行算法的编译器中可用。
仅当 `std::is_execution_policy_v<std::remove_cvref_t<executionpolicy>&gt;` 为 `true` 时，这些重载版本才参与重载决议。
不允许使用无序执行策略。</std::remove_cvref_t<executionpolicy>
:913
---
---
[c]visit_while
[c]visit_while
```c++ template<class F> bool visit_while(F f); template<class F> bool visit_while(F f) const; template<class F> bool cvisit_while(F f) const; ```
```c++ template<class f=""> bool visit_while(F f); template<class f=""> bool visit_while(F f) const; template<class f=""> bool cvisit_while(F f) const; ```</class></class></class>
Successively invokes `f` with references to each of the elements in the table until `f` returns `false` or all the elements are visited. Such references to the elements are const iff `*this` is const.
依次以哈希表中每个元素的引用调用函数 `f`，直到 `f` 返回 `false` 或遍历完所有元素。当且仅当 `*this` 为常量时，元素的引用为常量引用。
Returns:;; `false` iff `f` ever returns `false`.
返回值：;; 当且仅当 `f` 曾返回 `false` 时，返回 `false`。
:930
---
---
Parallel [c]visit_while
并行 ++[++c++]++visit++_++while
```c++ template<class ExecutionPolicy, class F> bool visit_while(ExecutionPolicy&& policy, F f); template<class ExecutionPolicy, class F> bool visit_while(ExecutionPolicy&& policy, F f) const; template<class ExecutionPolicy, class F> bool cvisit_while(ExecutionPolicy&& policy, F f) const; ```
```c++ template<class executionpolicy,="" class="" f=""> bool visit_while(ExecutionPolicy&amp;&amp; policy, F f); template<class executionpolicy,="" class="" f=""> bool visit_while(ExecutionPolicy&amp;&amp; policy, F f) const; template<class executionpolicy,="" class="" f=""> bool cvisit_while(ExecutionPolicy&amp;&amp; policy, F f) const; ```</class></class></class>
Invokes `f` with references to each of the elements in the table until `f` returns `false` or all the elements are visited. Such references to the elements are const iff `*this` is const. Execution is parallelized according to the semantics of the execution policy specified.
以哈希表中每个元素的引用调用函数 `f`，直到 `f` 返回 `false` 或遍历完所有元素。当且仅当 `*this` 为常量时，元素的引用为常量引用。执行过程将根据指定执行策略的语义进行并行化处理。
Returns:;; `false` iff `f` ever returns `false`. Throws:;; Depending on the exception handling mechanism of the execution policy used, may call `std::terminate` if an exception is thrown within `f`. Notes:;; Only available in compilers supporting C++17 parallel algorithms. + + These overloads only participate in overload resolution if `std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>` is `true`. + + Unsequenced execution policies are not allowed. + + Parallelization implies that execution does not necessary finish as soon as `f` returns `false`, and as a result `f` may be invoked with further elements for which the return value is also `false`.
返回值：;; 当且仅当 `f` 曾返回 `false` 时，返回 `false`。
抛出异常：;; 依据所使用执行策略的异常处理机制，若 `f` 内部抛出异常，则可能调用 `std::terminate`。
注意：;; 仅在支持 C++17 并行算法的编译器中可用。
仅当 `std::is_execution_policy_v<std::remove_cvref_t<executionpolicy>&gt;` 为 `true` 时，这些重载版本才参与重载决议。
不允许使用无序执行策略。
并行化意味着：一旦 `f` 返回 `false`，执行流程**不一定会立即终止**，因此 `f` 可能还会被继续用于后续元素，且这些调用的返回值同样为 `false`。</std::remove_cvref_t<executionpolicy>
:957
---
---
Size and Capacity
大小与容量
empty
空
```c++ [[nodiscard]] bool empty() const noexcept; ```
```c++ [[nodiscard]] bool empty() const noexcept; ```
Returns:;; `size() == 0`
返回值：;; `size() == 0`（容器为空时返回 true，否则返回 false）
:970
---
---
size
大小
```c++ size_type size() const noexcept; ```
```c++ size_type size() const noexcept; ```
Returns:;; The number of elements in the table.
返回值：;; 哈希表中的元素总数。
Notes:;; In the presence of concurrent insertion operations, the value returned may not accurately reflect the true size of the table right after execution.
注意：;; 在存在并发插入操作时，返回的值可能无法精确反映函数执行完成后哈希表的真实大小。
:985
---
---
max_size
max_size
```c++ size_type max_size() const noexcept; ```
```c++ size_type max_size() const noexcept; ```
Returns:;; `size()` of the largest possible table.
返回值：;; 哈希表能容纳的最大元素数量（最大容量）。
:996
---
---
Modifiers
修改器
emplace
原地构造
```c++ template<class... Args> bool emplace(Args&&... args); ```
```c++ template<class... args=""> bool emplace(Args&amp;&amp;... args); ```</class...>
Inserts an object, constructed with the arguments `args`, in the table if and only if there is no element in the table with an equivalent key.
当且仅当哈希表中不存在等价键的元素时，才会使用参数 `args` 构造对象并插入到哈希表中。
Requires:;; `value_type` is constructible from `args`. Returns:;; `true` if an insert took place. Concurrency:;; Blocking on rehashing of `*this`. Notes:;; If `args...` is of the form `k,v`, it delays constructing the whole object until it is certain that an element should be inserted, using only the `k` argument to check.
要求：;; `value_type` 可由参数 `args` 构造。
返回值：;; 成功插入元素时返回 `true`。
并发特性：;; 当对当前对象执行重哈希操作时会阻塞。
注意：;; 若 `args...` 格式为 `k,v`，则会仅使用参数 `k` 进行键检查，**直到确定需要插入元素时**，才会构造完整对象。
English Chinese (Simplified Han script) Actions
Complexity:;; O(`bucket_count()`)
复杂度：;; O(`bucket_count()`)
Initializer List Constructor
初始化列表构造函数
Constructs an empty table with at least `n` buckets, using `hf` as the hash function, `eql` as the key equality predicate and `a`, and inserts the elements from `il` 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 `il` 中的元素插入其中。
Constructs an empty table with at least `n` buckets, using `hf` as the hash function, the default hash function and key equality predicate and `a` as the allocator.
构造一个至少包含 `n` 个桶的空哈希表，使用 `hf` 作为哈希函数，默认键相等谓词，并以 `a` 作为分配器。
initializer_list Constructor with Bucket Count and Hasher and Allocator
带桶数、哈希函数和分配器的初始化列表构造函数
Note:;; The destructor is applied to every element, and all memory is deallocated
注意：;; 析构函数会作用于所有元素，且所有内存都会被释放
Concurrency:;; Blocking on `*this` and `other`.
并发：;; 阻塞 `*this` 与 `other`
Initializer List Assignment
初始化列表赋值
Returns:;; The number of elements visited (0 or 1). Notes:;; The `template<class K, class F>` overloads only participate in overload resolution if `Hash::is_transparent` and `Pred::is_transparent` are valid member typedefs. The library assumes that `Hash` is callable with both `K` and `Key` and that `Pred` is transparent. This enables heterogeneous lookup which avoids the cost of instantiating an instance of the `Key` type.
返回值：;; 访问的元素数量（0 或 1）。
注意：;; 仅当 `Hash::is_transparent` 与 `Pred::is_transparent` 为合法成员别名时，`template<class k,="" class="" f="">` 重载版本才会参与重载决议。库假定 `Hash` 可同时以 `K` 类型与 `Key` 类型调用，且 `Pred` 是透明的。这支持异构查找，避免了实例化 `Key` 类型对象的开销。</class>
Although functionally equivalent to individually invoking xref:concurrent_node_map_cvisit[`[c\]visit`] for each key, bulk visitation performs generally faster due to internal streamlining optimizations. It is advisable that `std::distance(first,last)` be at least xref:#concurrent_node_map_constants[`bulk_visit_size`] to enjoy a performance gain: beyond this size, performance is not expected to increase further.
尽管功能上等同于对每个键单独调用 `[c]visit`，但得益于内部的流式优化，批量访问通常性能更高。建议当 `std::distance(first,last)` 至少达到 `bulk_visit_size` 时使用批量访问以获得性能提升；超过该大小后，性能不会进一步提升。
[c]visit_while
[c]visit_while
```c++ template<class F> bool visit_while(F f); template<class F> bool visit_while(F f) const; template<class F> bool cvisit_while(F f) const; ```
```c++ template<class f=""> bool visit_while(F f); template<class f=""> bool visit_while(F f) const; template<class f=""> bool cvisit_while(F f) const; ```</class></class></class>
Successively invokes `f` with references to each of the elements in the table until `f` returns `false` or all the elements are visited. Such references to the elements are const iff `*this` is const.
依次以哈希表中每个元素的引用调用函数 `f`，直到 `f` 返回 `false` 或遍历完所有元素。当且仅当 `*this` 为常量时，元素的引用为常量引用。
Invokes `f` with references to each of the elements in the table until `f` returns `false` or all the elements are visited. Such references to the elements are const iff `*this` is const. Execution is parallelized according to the semantics of the execution policy specified.
以哈希表中每个元素的引用调用函数 `f`，直到 `f` 返回 `false` 或遍历完所有元素。当且仅当 `*this` 为常量时，元素的引用为常量引用。执行过程将根据指定执行策略的语义进行并行化处理。
Returns:;; `false` iff `f` ever returns `false`. Throws:;; Depending on the exception handling mechanism of the execution policy used, may call `std::terminate` if an exception is thrown within `f`. Notes:;; Only available in compilers supporting C++17 parallel algorithms. + + These overloads only participate in overload resolution if `std::is_execution_policy_v<std::remove_cvref_t<ExecutionPolicy>>` is `true`. + + Unsequenced execution policies are not allowed. + + Parallelization implies that execution does not necessary finish as soon as `f` returns `false`, and as a result `f` may be invoked with further elements for which the return value is also `false`.
返回值：;; 当且仅当 `f` 曾返回 `false` 时，返回 `false`。
抛出异常：;; 依据所使用执行策略的异常处理机制，若 `f` 内部抛出异常，则可能调用 `std::terminate`。
注意：;; 仅在支持 C++17 并行算法的编译器中可用。
仅当 `std::is_execution_policy_v<std::remove_cvref_t<executionpolicy>&gt;` 为 `true` 时，这些重载版本才参与重载决议。
不允许使用无序执行策略。
并行化意味着：一旦 `f` 返回 `false`，执行流程**不一定会立即终止**，因此 `f` 可能还会被继续用于后续元素，且这些调用的返回值同样为 `false`。</std::remove_cvref_t<executionpolicy>
Returns:;; `size() == 0`
返回值：;; `size() == 0`（容器为空时返回 true，否则返回 false）
size
大小
```c++ size_type size() const noexcept; ```
```c++ size_type size() const noexcept; ```
Returns:;; The number of elements in the table.
返回值：;; 哈希表中的元素总数。
max_size
max_size
```c++ size_type max_size() const noexcept; ```
```c++ size_type max_size() const noexcept; ```
Returns:;; `size()` of the largest possible table.
返回值：;; 哈希表能容纳的最大元素数量（最大容量）。
Modifiers
修改器
emplace
原地构造
```c++ template<class... Args> bool emplace(Args&&... args); ```
```c++ template<class... args=""> bool emplace(Args&amp;&amp;... args); ```</class...>
Copy Insert
复制插入
```c++ bool insert(const value_type& obj); bool insert(const init_type& obj); ```
```c++ bool insert(const value_type&amp; obj); bool insert(const init_type&amp; obj); ```
Requires:;; `value_type` is https://en.cppreference.com/w/cpp/named_req/CopyInsertable[CopyInsertable^]. Returns:;; `true` if an insert took place. + Concurrency:;; Blocking on rehashing of `*this`. Notes:;; A call of the form `insert(x)`, where `x` is equally convertible to both `const value_type&` and `const init_type&`, is not ambiguous and selects the `init_type` overload.
要求：;; `value_type` 满足 https://en.cppreference.com/w/cpp/named_req/CopyInsertable[CopyInsertable^] 要求。返回值：;; 成功执行插入操作则返回 `true`。并发特性：;; 对当前对象执行重哈希操作时会发生阻塞。注意：;; 若调用形式为 `insert(x)`，且 `x` 可同时隐式转换为 `const value_type&amp;` 与 `const init_type&amp;`，该调用不存在歧义，会选用 `init_type` 重载版本。
Requires:;; `value_type` is https://en.cppreference.com/w/cpp/named_req/MoveInsertable[MoveInsertable^]. Returns:;; `true` if an insert took place. Concurrency:;; Blocking on rehashing of `*this`. Notes:;; A call of the form `insert(x)`, where `x` is equally convertible to both `value_type&&` and `init_type&&`, is not ambiguous and selects the `init_type` overload.
要求：;; `value_type` 满足 https://en.cppreference.com/w/cpp/named_req/MoveInsertable[MoveInsertable^] 要求。
返回值：;; 成功执行插入操作则返回 `true`。
并发特性：;; 对当前对象执行重哈希操作时会发生阻塞。
注意：;; 若调用形式为 `insert(x)`，且 `x` 可同时转换为 `value_type&amp;&amp;` 与 `init_type&amp;&amp;`，该调用不存在歧义，会选用 `init_type` 重载版本。
```c++ size_type insert(std::initializer_list<value_type> il); ```
```c++ size_type insert(std::initializer_list<value_type> il); ```</value_type>

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Returns:;; `size() == 0`
Returns:返回值：;; `size() == 0`（容器为空时返回 true，否则返回 false）
06/05/2026
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Returns:;; `size() == 0`
Returns:;; `size() == 0`
06/05/2026
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Flags
safe-html, strict-same
Unit identifier
51954
Source string location
:968
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 202