[R] Which system.time() component to use?
ggrothendieck at gmail.com
Sun Feb 28 05:55:26 CET 2010
The last component seems the most meaningful since its the amount of
time you actually waited for the code to run.
On Sat, Feb 27, 2010 at 11:44 PM, Ravi Varadhan <rvaradhan at jhmi.edu> wrote:
> Thanks, Gabor. Your reply is helpful, but it still doesn't answer whether I should use the sum of the first two components of system.time (user + system CPU) or only the first one (user CPU).
> Ravi Varadhan, Ph.D.
> Assistant Professor,
> Division of Geriatric Medicine and Gerontology
> School of Medicine
> Johns Hopkins University
> Ph. (410) 502-2619
> email: rvaradhan at jhmi.edu
> ----- Original Message -----
> From: Gabor Grothendieck <ggrothendieck at gmail.com>
> Date: Saturday, February 27, 2010 9:47 pm
> Subject: Re: [R] Which system.time() component to use?
> To: Ravi Varadhan <rvaradhan at jhmi.edu>
> Cc: r-help at r-project.org
>> Try this:
>> > system.time(Sys.sleep(60))
>> user system elapsed
>> 0.00 0.00 60.05
>> > pt <- proc.time(); Sys.sleep(60); proc.time() - pt
>> user system elapsed
>> 0.00 0.00 60.01
>> On Sat, Feb 27, 2010 at 9:33 PM, Ravi Varadhan <rvaradhan at jhmi.edu> wrote:
>> > Hi,
>> > The `system.time(expr)' command provide 3 different times for
>> evaluating the expression `expr'; the first two are user and system
>> CPUs and the third one is total elapsed time. Suppose I want to
>> compare two different computational procedures for performing the same
>> task, which component of `system.time' is most meaningful in the sense
>> that it most accurately reflects the computational effort of the
>> algorithm, and does not depend upon the idiosyncrasies of the
>> operating system.
>> > I have always been using the first component of `system.time', which
>> is the user CPU. Should I use the sum of user and system CPU or is
>> the total elapsed time a better measure? I would appreciate UseR's
>> feedback on this.
>> > Thanks very much.
>> > Best,
>> > Ravi.
>> > ____________________________________________________________________
>> > Ravi Varadhan, Ph.D.
>> > Assistant Professor,
>> > Division of Geriatric Medicine and Gerontology
>> > School of Medicine
>> > Johns Hopkins University
>> > Ph. (410) 502-2619
>> > email: rvaradhan at jhmi.edu
>> > ______________________________________________
>> > R-help at r-project.org mailing list
>> > PLEASE do read the posting guide
>> > and provide commented, minimal, self-contained, reproducible code.
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