On Wednesday, December 06, 2017 09:12:08 helxi via Digitalmars-d-learn
wrote:
> void main()
> {
> import std.stdio, std.datetime;
>
> auto t0 = Clock.currTime;
> writeln(fib(100_000));
> writeln(Clock.currTime - t0);
> }
On a complete sidenote, if you want to correctly time stuff, you should use
a monotonic clock rather than the wall clock, since the wall clock can be
shifted by the system, whereas a monotonic clock is guaranteed to always
move forward at a fixed rate. So, you'd either want to do something like
import std.stdio, std.datetime;
auto t0 = MonoTime.currTime;
writeln(fib(100_000));
writeln(MonoTime.currTime - t0);
or
import std.stdio, std.datetime.stopwatch;
auto sw = StopWatch(AutoStart.yes);
writeln(fib(100_000));
writeln(sw.peek);
That way, you don't have to worry about the timing being wrong due to the
clock being shifted. Such shifting happens infrequently enough that it won't
_usually_ create a problem, but it can create a serious problem if a shift
occurs and you're doing something like waiting for the clock to reach a
certain point in time. It's just better to get in the habit of using the
monotonic clock for timing stuff.
Note however that for the time being, if you want to use anything in
std.datetime.stopwatch, you'll need to either just import it and not
std.datetime or use selective import such as
import std.datetime.stopwatch : StopWatch;
This is because the old versions of the benchmarking stuff like benchmark
and StopWatch are in std.datetime.package and have been deprecated (they use
core.time.TickDuration which will soon be deprecated) and replaced with
nearly identical versions in std.datetime.stopwatch which use
core.time.MonoTime and core.time.Duration. Until the old versions have gone
through the full deprecation cycle and have been removed, they'll conflict
with the new ones, so std.datetime.stopwatch is not yet publicly imported in
std.datetime.package, and if you import both, then selective imports are
needed in order to deal with the symbol conflict.
- Jonathan M Davis
