A marginally faster mutable hash table is not really useful for much. If that 30% speedup or whatever is going to make or break your application, a single hash

A marginally faster mutable hash table is not really useful for much. If that 30% speedup or whatever is going to make or break your application, a single hash table was the wrong choice anyway. If this is the kind of thing that keeps you up at night, you should just be using C.