[R] Which system.time() component to use?

[Gabor Grothendieck]

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.
> ____________________________________________________________________
>
> 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.
>> >
>