Hi I'm the author for this post. My general guideline is figure out where your bottleneck is, and optimize on the hotspot first. In your description, I can only

Hi I'm the author for this post. My general guideline is figure out where your bottleneck is, and optimize on the hotspot first. In your description, I can only try my best to guess where the bottleneck could possibly be... First of all: "I often need lots of small hash maps". Do you maintain multiple small hash maps at the same time? Then the data structure holding this many hash maps may be your bottleneck instead of the hash map itself. Another possibility is you have some small hash map that get created and dropped rapidly. In this case you might want to hold it in memory so you don't have much allocation overhead. Other than these, the remaining optimization I can think of would be making your hash table compact (like what I did in this post). Reserving buckets with max load factor should give you a nice control of your hash table size. Reference: http://www.cplusplus.com/reference/unordered_map/unordered_map/reserve/ http://www.cplusplus.com/reference/unordered_map/unordered_m...