alt Hacker NewsThe thing I ran into most recently is that std::chrono (weirdly?) only supports clocks with compile-time fixed fractional conversion to reference time (~seconds). E.g., you can't implement a std::chrono clock where the count() unit is the native CPU's cycle counter, which will have some runtime-determined conversion to seconds. The types make it impossible.
std::chrono counts the number of ticks of a given periodicity. The periodicity does have to be a known compile-time ratio expressible as a fraction of seconds, but you can use a floating-type type to count the number of ticks.
std::chrono is meant to take advantage of information about periodicity at compile time, but if you want to count in terms of a dynamic periodicity not known until runtime, you can still do things. E.g. use time_t and some wrapper functions, or just pick one (or several) std::chrono base durations such as standardizing on nanoseconds, and then just count floating-point ticks.