Intel® oneAPI Threading Building Blocks Developer Guide and API Reference
Deduction guides
If possible, concurrent_unordered_multimap constructors support class template argument deduction (since C++17). Copy and move constructors, including constructors with an explicit allocator_type argument, provide implicitly-generated deduction guides. In addition, the following explicit deduction guides are provided:
template <typename InputIterator,
typename Hash = std::hash<iterator_key_t<InputIterator>>,
typename KeyEqual = std::equal_to<iterator_key_t<InputIterator>>,
typename Allocator = tbb::tbb_allocator<iterator_alloc_value_t<InputIterator>>>
concurrent_unordered_multimap( InputIterator, InputIterator,
map_size_type = {},
Hash = Hash(),
KeyEqual = KeyEqual(),
Allocator = Allocator() )
-> concurrent_unordered_multimap<iterator_key_t<InputIterator>,
iterator_mapped_t<InputIterator>,
Hash,
KeyEqual,
Allocator>;
template <typename InputIterator,
typename Hash,
typename Allocator>
concurrent_unordered_multimap( InputIterator, InputIterator,
map_size_type,
Hash,
Allocator )
-> concurrent_unordered_multimap<iterator_key_t<InputIterator>,
iterator_mapped_t<InputIterator>,
Hash,
std::equal_to<iterator_key_t<InputIterator>>,
Allocator>;
template <typename InputIterator,
typename Allocator>
concurrent_unordered_multimap( InputIterator, InputIterator,
map_size_type,
Allocator )
-> concurrent_unordered_multimap<iterator_key_t<InputIterator>,
iterator_mapped_t<InputIterator>,
std::hash<iterator_key_t<InputIterator>>,
std::equal_to<iterator_key_t<InputIterator>>,
Allocator>;
template <typename Key,
typename T,
typename Hash = std::hash<std::remove_const_t<Key>>,
typename KeyEqual = std::equal_to<std::remove_const_t<Key>>,
typename Allocator = tbb::tbb_allocator<std::pair<const Key, T>>>
concurrent_unordered_multimap( std::initializer_list<std::pair<Key, T>>,
map_size_type = {},
Hash = Hash(),
KeyEqual = KeyEqual(),
Allocator = Allocator() )
-> concurrent_unordered_multimap<std::remove_const_t<Key>,
T,
Hash,
KeyEqual,
Allocator>;
template <typename Key,
typename T,
typename Allocator>
concurrent_unordered_multimap( std::initializer_list<std::pair<Key, T>>,
map_size_type,
Allocator )
-> concurrent_unordered_multimap<std::remove_const_t<Key>,
T,
std::hash<std::remove_const_t<Key>>,
std::equal_to<std::remove_const_t<Key>>,
Allocator>;
template <typename Key,
typename T,
typename Allocator>
concurrent_unordered_multimap( std::initializer_list<std::pair<Key, T>>,
Allocator )
-> concurrent_unordered_multimap<std::remove_const_t<Key>,
T,
std::hash<std::remove_const_t<Key>>,
std::equal_to<std::remove_const_t<Key>>,
Allocator>;
template <typename Key,
typename T,
typename Hash,
typename Allocator>
concurrent_unordered_multimap( std::initializer_list<std::pair<Key, T>>,
map_size_type,
Hash,
Allocator )
-> concurrent_unordered_multimap<std::remove_const_t<Key>,
T,
Hash,
std::equal_to<std::remove_const_t<Key>>,
Allocator>;
Where the map_size_type type refers to the size_type member type of the deduced concurrent_unordered_multimap and the type aliases iterator_key_t, iterator_mapped_t, and iterator_alloc_value_t are defined as follows:
template <typename InputIterator>
using iterator_key_t = std::remove_const_t<typename std::iterator_traits<InputIterator>::value_type::first_type>;
template <typename InputIterator>
using iterator_mapped_t = typename std::iterator_traits<InputIterator>::value_type::second_type;
template <typename InputIterator>
using iterator_alloc_value_t = std::pair<std::add_const_t<iterator_key_t<InputIterator>,
iterator_mapped_t<InputIterator>>>;
These deduction guides only participate in the overload resolution if the following requirements are met:
The InputIterator type meets the InputIterator requirements described in the [input.iterators] section of the ISO C++ Standard.
The Allocator type meets the Allocator requirements described in the [allocator.requirements] section of the ISO C++ Standard.
The Hash type does not meet the Allocator requirements.
The KeyEqual type does not meet the Allocator requirements.
Example
#include <oneapi/tbb/concurrent_unordered_map.h>
#include <vector>
#include <functional>
struct CustomHasher {...};
int main() {
std::vector<std::pair<int, float>> v;
// Deduces m1 as concurrent_unordered_multimap<int, float>
oneapi::tbb::concurrent_unordered_multimap m1(v.begin(), v.end());
// Deduces m2 as concurrent_unordered_multimap<int, float, CustomHasher>;
oneapi::tbb::concurrent_unordered_multimap m2(v.begin(), v.end(), CustomHasher{});
}