Iterating over the contents of concurrent_hash_map

Question

I am using tbb::concurrent_hash_map. I understand insertion and deletion are safe operations. Is iterating over hash map considered safe with respect to insertion and deletion. If not are there any data structures which I can use for safe iteration.

Answer 1

With the absence of memory reclamation support (GC) in C++ and TBB, it is not possible to make both deletion and iteration safe at the same time without significant performance impact. Thus TBB has 2 concurrent containers for hash tables:

• concurrent_hash_map with safe erase() and element-level access synchronization but without safe iteration .
• concurrent_unordered_* (eg concurrent_unordered_map ) without safe erase() and element access synchronization but with thread-safe iteration support.