One other thing, in a multiprocessor configuration, if your application is
making use of the additional CPUs, then
User + System > Elapsed
In some cases.
On 7/4/07, jim holtman <[EMAIL PROTECTED]> wrote:
>
> User and System are a measure of the CPU time that was consumed. Elapsed
> time is the "wall clock" and even though they are both measured in seconds,
> they are not really the same units. The reason for the difference is any
> "idle" time that they system may have waiting for I/O to complete which does
> not consume CPU time for your process, but does consume Elasped time.
>
> For some instances of CPU intensive code (with no I/O of competing tasks),
> the User + System ~= Elapsed. Also you have to take into account the
> granularity of the clock when looking at numbers like 0.04. So serious
> comparisons of timing, you want runs of at least 10s of seconds or more.
>
>
> On 7/4/07, Stefan Grosse <[EMAIL PROTECTED]> wrote:
> >
> > Gabor Grothendieck wrote:
> > >> set.seed(1)
> > >> C <- sample(c("a", "b"), 100000, replace = TRUE)
> > >> system.time(s1 <- ifelse(C == "a", 1, -1))
> > >>
> > > user system elapsed
> > > 0.37 0.01 0.38
> > >
> > >> system.time(s2 <- 2 * (C == "a") - 1)
> > >>
> > > user system elapsed
> > > 0.02 0.00 0.02
> > >
> > > system.time(s1 <- ifelse(C == "a", 1, -1))
> > user system elapsed
> > 0.04 0.01 0.08
> > > system.time(s2 <- 2 * (C == "a") - 1)
> > user system elapsed
> > 0 0 0
> >
> >
> > I am just wondering: how comes the time does add up to 0.05 while
> > elapsed states 0.08 on my system? (Vista+R2.5.1)
> >
> > Stefan
> >
> >
> > -=-=-
> > ... Time is an illusion, lunchtime doubly so. (Ford Prefect)
> >
> > ______________________________________________
> > R-help@stat.math.ethz.ch mailing list
> > https://stat.ethz.ch/mailman/listinfo/r-help
> > PLEASE do read the posting guide
> > http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
> > and provide commented, minimal, self-contained, reproducible code.
> >
>
>
>
> --
> Jim Holtman
> Cincinnati, OH
> +1 513 646 9390
>
> What is the problem you are trying to solve?
--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
What is the problem you are trying to solve?
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