On Mon, 15 Jan 2007 10:46:37 George Warner <email@hidden> wrote:
> Just for the record UpTime (and CFAbsoluteTimeGetCurrent and
> mach_absolute_time) is still the lowest-overhead and highest precision clock
> on PPC or Intel. (IIRC UpTime & CFAbsoluteTimeGetCurrent both call directly
> thru to mach_absolute_time now.)
>
> #import <mach/mach_time.h>
>
> uint64_t t0 = mach_absolute_time();
>
> // do your timed stuff here!
>
> uint64_t t1 = mach_absolute_time();
>
> // compute the delta
> uint64_t t = t1 - t0;
>
> // this is the timebase info
> mach_timebase_info_data_t info;
> mach_timebase_info(&info);
> double nano = 1e-9 * ( (double) info.numer) / ((double) info.denom);
For the record, how aggressively may we cache the result of
mach_timebase_info? Is it guaranteed to be a constant for a
program run or could it change with e.g. the change of
processor speed?
Mike
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