# Concurrently unsafe modifiers

All member functions in this section can only be performed serially. The behavior is undefined in case of concurrent execution of these member functions with other (either concurrently safe) methods.

## clear

>     void clear();

> Removes all elements from the container.

## swap

>     void swap( concurrent_hash_map& other );

> Swaps contents of `*this` and `other`.

> Swaps allocators if `std::allocator_traits<allocator_type>::propagate_on_container_swap::value` is `true`.

> Otherwise, if `get_allocator() != other.get_allocator()`, the behavior is undefined.