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

hrr has asked for the wisdom of the Perl Monks concerning the following question:

In Time::Hires, there are two simple ways to measure time intervals, namely

   use Time::HiRes qw(gettimeofday tv_interval);
   $t0 = [gettimeofday];
   $elapsed = tv_interval($t0)
[download]

   use Time::HiRes qw(time);
   $t0 = time;
   $elapsed = time - $t0;
[download]

Is one of these two methods preferrable, considering accuracy and performance? As both gettimeofday and time provide accuracy up to microseconds, it seems to me that the accuracy of both time intervals are equivalent.

Thank you for your help!

Update: added use Time::HiRes to the code above.

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

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Re: Measuring time intervals using Time::HiRes -- time vs. gettimeofday and tv_interval by shonorio (Hermit) on Jul 18, 2006 at 19:14 UTC
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 - $t0; }, });` [download] ... result ... `Rate Hires Time Hires 100260/s -- -58% Time 240043/s 139% --` [download] Solli Moreira Honorio Sao Paulo - Brazil	[reply] [d/l] [select]
Re^2: Measuring time intervals using Time::HiRes -- time vs. gettimeofday and tv_interval by hrr (Monk) on Jul 18, 2006 at 19:33 UTC
Thank you for this hint! I obtained similar benchmark results as you did. Surprsingly, using `Time::HiRes::time` instead of the standard `time`, the performance is much better (but still worse than tv_interval): `Rate Hires Time Hires 98201/s -- -55% Time 220149/s 124% --` [download]	[reply] [d/l] [select]
Re^3: Measuring time intervals using Time::HiRes -- time vs. gettimeofday and tv_interval by Ieronim (Friar) on Jul 18, 2006 at 19:53 UTC
Vice versa. Look at the Rate column — it shows the speed of the function! The more times a second the function is called, the faster it is :) So in this table (produced by the benchmark involving all three variants) `Rate interval HiRes::time buitin time() interval 88470/s -- -53% -95% HiRes::time 188363/s 113% -- -89% buitin time() 1753092/s 1882% 831% --` [download] builtin time() is 9 times faster than Time::HiRes::time, which is nearly 2 times faster than the weird variant with tv_interval! Benchmark code is here: Read more... (754 Bytes) `s;;Just-me-not-h-Ni-m-P-Ni-lm-I-ar-O-Ni;;tr?IerONim-?HAcker ?d;print`	[reply] [d/l] [select]
Re^4: Measuring time intervals using Time::HiRes -- time vs. gettimeofday and tv_interval by Tanktalus (Canon) on Jul 18, 2006 at 20:21 UTC
Re: Measuring time intervals using Time::HiRes -- time vs. gettimeofday and tv_interval by kwaping (Priest) on Jul 18, 2006 at 22:53 UTC
Here's the source for `tv_interval`: `sub tv_interval { # probably could have been done in C my ($a, $b) = @_; $b = [gettimeofday()] unless defined($b); (${$b}[0] - ${$a}[0]) + ((${$b}[1] - ${$a}[1]) / 1_000_000); }` [download] That should explain everything, I think. --- It's all fine and dandy until someone has to look at the code.	[reply] [d/l] [select]