I ran into these problems with std::unordered_map. While developing my game, I would always run it in debug mode because I need to debug it. Loading a game world was taking around 12 seconds, and it was beginning to grate on me because of the increased iteration times. So I decided to profile it and see what was taking so long. I compiled in release mode to begin debugging, and it magically took the world load time down to 2 seconds.
I wondered what code I had written that caused such a massive performance hit in debug mode. So I went to profile my code in a debug build to find out. Lo and behold, something like 90% of the CPU time was wasted doing lookups from std::unordered_map because of debug iterators. I tried everything I could to just turn debug iterators off, and eventually gave up and switched to robin_hood::unordered_map which runs great in debug and release. Now I have an unwarranted aversion to the std lib, even though it really is great so long as you're running it in release mode.
I wondered what code I had written that caused such a massive performance hit in debug mode. So I went to profile my code in a debug build to find out. Lo and behold, something like 90% of the CPU time was wasted doing lookups from std::unordered_map because of debug iterators. I tried everything I could to just turn debug iterators off, and eventually gave up and switched to robin_hood::unordered_map which runs great in debug and release. Now I have an unwarranted aversion to the std lib, even though it really is great so long as you're running it in release mode.