I am using auto-complete-mode with ac-c-headers and whenever I type std:: There is a long (~30 seconds) pause, presumably while the candidates list is populated. This happens every time, which suggests that there is no caching to speed things up for the next time.
Is there a way to avoid the pause after every time I type std::?
Update
Using the emacs profiler, I have now discovered that the pretty much all of the time is being spent in the functions semantic-analyze-possible-completions and semantic-analyze-current-context. This suggests that the real problem probably lies with semantic. I have also learned that including anything from the Boost libraries causes a significant increase in the amount of time required for semantic to return possible completions.
(In case it makes a difference, I am using Emacs 24.5 on Linux)