Beefy Boxes and Bandwidth Generously Provided by pair Networks
Perl: the Markov chain saw
 
PerlMonks  

Re^2: Anything better than 'times' ?

by gone2015 (Deacon)
on Sep 17, 2008 at 18:18 UTC ( #712087=note: print w/ replies, xml ) Need Help??


in reply to Re: Anything better than 'times' ?
in thread Anything better than 'times' ?

I had tried Time::HiRes::clock(), but that gives the same resolution as times. So I thought that was a dead end.

However, I went back and read again. There are Time::HiRes::clock_gettime($which) and Time::HiRes::getres($which). Where the $which is the name of a POSIX high resolution timer. I confess I had assumed that this was wall-clock.

The POSIX timer CLOCK_REALTIME claims a resolution of 1E-9 on my machine. Hurrah :-) However, that is wall-clock. Boo :-(

The Time::HiRes hints that there may be other timers... so, I went digging in the POSIX documentation. I found CLOCK_PROCESS_CPUTIME_ID, which does what the name suggests, and also claims a resolution of 1E-9 on my machine. Hurrah !

Conclusion, yes: turns out that Time::HiRes is the answer -- thank you. To know that, however, you need to know that:

  • there is a "clock" called CLOCK_PROCESS_CPUTIME_ID -- provided you have a POSIX compliant system, and _POSIX_CPUTIME is defined (which is discovered using getconf).
  • that you use can import that name from Time::HiRes and use it with Time::HiRes::clock_gettime($which) and Time::HiRes::getres($which) to access the timer.
  • there is also a "clock" called CLOCK_THREAD_CPUTIME_ID, which is available if _POSIX_THREAD_CPUTIME is defined.
So, for my purposes:
use Time::HiRes qw(clock_gettime CLOCK_PROCESS_CPUTIME_ID) ; $start = clock_gettime(CLOCK_PROCESS_CPUTIME_ID) ; # replaces $start + = (times)[0] ... $end = clock_gettime(CLOCK_PROCESS_CPUTIME_ID) ; # replaces $end + = (times)[0]
is the trick -- which I note in case it's of use to anyone like me who knew nothing of it until today.


Comment on Re^2: Anything better than 'times' ?
Select or Download Code

Log In?
Username:
Password:

What's my password?
Create A New User
Node Status?
node history
Node Type: note [id://712087]
help
Chatterbox?
and the web crawler heard nothing...

How do I use this? | Other CB clients
Other Users?
Others pondering the Monastery: (13)
As of 2015-07-03 11:44 GMT
Sections?
Information?
Find Nodes?
Leftovers?
    Voting Booth?

    The top three priorities of my open tasks are (in descending order of likelihood to be worked on) ...









    Results (51 votes), past polls