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

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

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]

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