Re: large inaccuracies in Time::HiRes on Opteron

From: Big and Blue (No_4_at_dsl.pipex.com)
Date: 02/26/05

  • Next message: David Christensen: "Re: proposal for new module -- Math::TriangularNumbers" 
    Date: Sat, 26 Feb 2005 22:55:45 +0000

    Harry Mangalam wrote:
    >
    > I'm using the Time::HiRes module on a dual opteron running:
    >.....
    > on the AMD platform, I'm getting very strange results.
    >...
    > typically, I'll get one high and one low extreme for each 50 run test and
    > typically tests whch involve running lots of different tests which use it
    > will show much more variation than a single test that uses the calls
    > repeatedly (the case above is from one script that repeats identical runs).

        There was an issue with the IBM Summit chipset (fixed in 2.4.15 IIRC)
    which caused Timer::Hires to do odd things on IBM x400 series.

        The symptoms could be seen by just runnning a simple C program which
    looped doing gettimeofday() calls with 1s sleeps in between. Occassionally
    (20% of the time?) the result would be out by something like 1.2s (either
    forwards or backwards). Perhaps you are seeing something similar here? 

    -- 
              Just because I've written it doesn't mean that
                   either you or I have to believe it.
  • Next message: David Christensen: "Re: proposal for new module -- Math::TriangularNumbers"