Deduction guides

Where possible, constructors of concurrent_unordered_multimap support class template argument deduction (since C++17):

template <typename InputIterator,
          typename Hash = std::hash<iterator_key_t<InputIterator>>,
          typename KeyEqual = std::equal_to<iterator_key_t<InputIterator>>,
          typename Allocator = tbb_allocator<iterator_alloc_value_t<InputIterator>>>
concurrent_unordered_multimap( InputIterator, InputIterator,
                               map_size_type = /*implementation_defined*/,
                               Hash = Hash(), KeyEqual = KeyEqual(),
                               Allocator = Allocator() )
-> concurrent_unordered_multimap<iterator_key_t<InputIterator>,
                                 iterator_mapped_t<InputIterator>,
                                 Hash, KeyEqual, 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 InputIterator,
          typename Allocator>
concurrent_unordered_multimap( InputIterator, InputIterator, 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 InputIterator,
          typename Hash,
          typename Allocator>
concurrent_unordered_multimap( InputIterator, InputIterator,
                          Hash, Allocator )
-> concurrent_unordered_multimap<iterator_key_t<InputIterator>,
                                 iterator_mapped_t<InputIterator>,
                                 Hash,
                                 std::equal_to<iterator_key_t<InputIterator>>,
                                 Allocator>;

template <typename Key,
          typename T,
          typename Hash = std::hash<Key>,
          typename KeyEqual = std::equal_to<Key>,
          typename Allocator = tbb_allocator<std::pair<Key, T>>>
concurrent_unordered_multimap( std::initializer_list<value_type>,
                               map_size_type = /*implementation-defined*/,
                               Hash = Hash(),
                               KeyEqual = KeyEqual(),
                               Allocator = Allocator() )
-> concurrent_unordered_multimap<Key, T,
                                 Hash,
                                 KeyEqual,
                                 Allocator>;

template <typename Key,
          typename T,
          typename Allocator>
concurrent_unordered_multimap( std::initializer_list<value_type>,
                               map_size_type, Allocator )
-> concurrent_unordered_multimap<Key, T,
                                 std::hash<Key>,
                                 std::equal_to<Key>,
                                 Allocator>;

template <typename Key,
          typename T,
          typename Hash,
          typename Allocator>
concurrent_unordered_multimap( std::initializer_list<value_type>,
                               map_size_type, Hash, Allocator )
-> concurrent_unordered_multimap<Key, T,
                                 Hash,
                                 std::equal_to<Key>,
                                 Allocator>;

Where the type map_size_type refers to the size_type member type of the deduced concurrent_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>>>;

Example

#include <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>
    tbb::concurrent_unordered_multimap m1(v.begin(), v.end());

    // Deduces m2 as concurrent_unordered_multimap<int, float, CustomHasher>;
    tbb::concurrent_unordered_multimap m2(v.begin(), v.end(), CustomHasher{});
}