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Re^4: Measuring time intervals using Time::HiRes -- time vs. gettimeofday and tv_interval

by Tanktalus (Canon)
on Jul 18, 2006 at 20:21 UTC ( [id://562120]=note: print w/replies, xml ) Need Help??


in reply to Re^3: Measuring time intervals using Time::HiRes -- time vs. gettimeofday and tv_interval
in thread Measuring time intervals using Time::HiRes -- time vs. gettimeofday and tv_interval

As long as we're all tweaking the heck out of our benchmarks... ;-)

What I've noticed is the number of calls to these functions are not all the same. In the 'interval' function, we are calling gettimeofday, constructing an anonymous array, calling tv_interval, and destroying the array. Only one of these are we actually interested in. Meanwhile, both of the other two cases, we're calling *time twice. A completely different set of comparisons. I also eliminated the overhead of returning floats, what little that should be.

So, I thought I'd throw this into the mix. Put all the initialisation up front. Then see what happens.

#! /usr/bin/perl use warnings; use strict; use Time::HiRes qw(time); use Benchmark qw(:all) ; my $interval0 = [Time::HiRes::gettimeofday()]; my $hires0 = Time::HiRes::time(); my $time0 = time(); cmpthese(-1, { 'interval' => sub { my $elapsed = Time::HiRes::tv_interval($interval0); return; }, 'hires' => sub { my $elapsed = Time::HiRes::time() - $hires0; return; }, 'time' => sub { my $elapsed = time - $time0; return; }, });
And the results?
Rate interval time hires interval 685148/s -- -79% -80% time 3340426/s 388% -- -2% hires 3398163/s 396% 2% --
2% bonus to hires's time over the built-in time? I'll chalk that up to statistically insignificant, and call the two a tie. In fact, I ran it a second time and got it reversed:
Rate interval hires time interval 971246/s -- -77% -78% hires 4192706/s 332% -- -3% time 4327848/s 346% 3% --
So, I'd say that the difference between interval and time is non-trivial. But even that operates fast enough that I'm not going to worry about it.

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