Template class concurrent_hash_map supports forward iterators; that is, iterators that can advance only forwards across a table. Reverse iterators are not supported. Concurrent operations (count, find, insert, and erase) invalidate any existing iterators that point into the table, An exception to this rule is that count and find do not invalidate iterators if no insertions or erasures have occurred after the most recent call to method rehash.


Do not call concurrent operations, including count and find while iterating the table. Use concurrent_unordered_map if concurrent traversal and insertion are required.

The following table provides additional information on the members of this template class.
Member Description
iterator begin()

Returns: iterator pointing to beginning of key-value sequence.

iterator end()


iterator pointing to end of key-value sequence.

const_iterator begin() const

Returns: const_iterator pointing to the beginning of key-value sequence.

const_iterator end() const

Returns: const_iterator pointing to the end of key-value sequence.

std::pair<iterator, iterator> equal_range( const Key& key );

Returns: Pair of iterators (i,j) such that the half-open range [i,j) contains all pairs in the map (and only such pairs) with keys equal to key. Because the map has no duplicate keys, the half-open range is either empty or contains a single pair.


This method is serial alternative to concurrent count and find methods.

std::pair<const_iterator, const_iterator> equal_range( const Key& key ) const;

See std::pair<iterator, iterator> equal_range( const Key& key ).

For more complete information about compiler optimizations, see our Optimization Notice.