Re: Measuring time intervals using Time::HiRes -- time vs. gettimeofday and tv

By Benchmark, the second one is faster than the first code. If think you could benchmark you code with both code to be sure.

use Time::HiRes qw(time);
use Benchmark qw(:all) ;

# Use Perl code in strings...
cmpthese(-10, {
        'Hires' => sub { my $t0 = [Time::HiRes::gettimeofday];
                         my $elapsed = Time::HiRes::tv_interval($t0)}
        ,
        'Time' => sub { my $t0 = time;
                         my $elapsed = time - $t0;
        },
    });
[download]

... result ...

           Rate Hires  Time
Hires 100260/s    --  -58%
Time  240043/s  139%    --
[download]

Solli Moreira Honorio
Sao Paulo - Brazil

Comment on Re: Measuring time intervals using Time::HiRes -- time vs. gettimeofday and tv_interval Select or Download Code

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Re^2: Measuring time intervals using Time::HiRes -- time vs. gettimeofday and tv_interval by hrr (Monk) on Jul 18, 2006 at 19:33 UTC
Thank you for this hint! I obtained similar benchmark results as you did. Surprsingly, using `Time::HiRes::time` instead of the standard `time`, the performance is much better (but still worse than tv_interval): `Rate Hires Time Hires 98201/s -- -55% Time 220149/s 124% --` [download]	[reply] [d/l] [select]
Re^3: Measuring time intervals using Time::HiRes -- time vs. gettimeofday and tv_interval by Ieronim (Friar) on Jul 18, 2006 at 19:53 UTC
Vice versa. Look at the Rate column — it shows the speed of the function! The more times a second the function is called, the faster it is :) So in this table (produced by the benchmark involving all three variants) `Rate interval HiRes::time buitin time() interval 88470/s -- -53% -95% HiRes::time 188363/s 113% -- -89% buitin time() 1753092/s 1882% 831% --` [download] builtin time() is 9 times faster than Time::HiRes::time, which is nearly 2 times faster than the weird variant with tv_interval! Benchmark code is here: Read more... (754 Bytes) `s;;Just-me-not-h-Ni-m-P-Ni-lm-I-ar-O-Ni;;tr?IerONim-?HAcker ?d;print`	[reply] [d/l] [select]
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
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. Read more... (878 Bytes) And the results? `Rate interval time hires interval 685148/s -- -79% -80% time 3340426/s 388% -- -2% hires 3398163/s 396% 2% --` [download] 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% --` [download] 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.	[reply] [d/l] [select]