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

[Ravi Varadhan]

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.
> >