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

[Gabor Grothendieck]

Also you might want to try out this which will repeatedly run your
benchmarks to average out the values and make comparisons easier:

http://rbenchmark.googlecode.com



On Sat, Feb 27, 2010 at 11:55 PM, Gabor Grothendieck
<ggrothendieck at gmail.com> wrote:
> 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.
>>> >
>>
>