Long pause after typing `std::` when using semantic with auto-complete

Question

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)

Answer 1

I've hit this same problem before and I "solved" it by changing the value of ac-delay from 0.1s to 1.0, like so:

(set-variable 'ac-delay 1.0)

That means that as I'm typing it only attempts the auto-complete if I stop typing for a second. So if you know you want a std::vector you can just keep typing and auto-complete never fires.