I have a C++ program that maintains a boost::flat_map. It receives real-time commands in the form of (key, value). If value is 0, then the flat_map[key] should be deleted if it exists. If value is nonzero, then the flat_map[key] should be set to value in the flat_map if the entry already exists, or it should be inserted if the entry does not already exist.
However, the commands do not come one by one. Instead, they come in batches, and the program only needs the flat_map to be sorted after each entire batch of commands is processed. It does not need the flat_map to be sorted while in the middle of processing a batch of commands.
Given this flexibility, is there a way to reduce processing time by avoiding the flat_map overhead of moving many elements on each insertion/deletion, and only incurring that overhead once at the end of each batch? The program is very latency sensitive.
Appreciate any input you may have!
You can use extract_sequence / adopt_sequence to update the underlying vector, and so long as it ends up ordered and uniqued, there's only a pair of vector moves in overhead.
auto underlying = my_map.extract_sequence();
// merge underlying and batch
my_map.adopt_sequence(boost::ordered_unique_range_t{}, std::move(underlying));