[R] system.time question

[Jeff Newmiller]

You asked several questions.
Elapsed: yes
User + System = CPU: yes
Finally: You have to look at the load and/or cpu core count. Unless you setup your code to take advantage of multiple cores, R runs on a single core.
Also: Do you really need to ask that question?

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Sent from my phone. Please excuse my brevity.

Mark Leeds <markleeds2 at gmail.com> wrote:

>Hi : I looked at the help for system.time but I still have the
>following
>question. Can someone explain the output following output
>of system.time :
>
> user          system      elapsed
>12399.681  5632.352   56935.647
>
>Here's my take based on the fact that I was doing ps -aux | grep R off
>and
>on and the total amount of CPU minutes that
>got allotted before the job ended was about 5 hours and the total
>actual
>time that the job took was about 15 hours.
>
>Does elapsed = total actual time job taken ? That seems to be the case
>or a
>strange coincidence.
>
>Does user + system = CPU time from ps -aux | grep R ? That seems to be
>the
>case also or a weird coincidence.
>
>Finally, why can't the CPU get a higher percentage ? It's seems like
>it's
>always around 30% which would make sense since
>5 is ~ 30% of 15 hours.
>
>Also, assuming my take above is correct, when talking about timing of
>algorithms, in this case, does one say the job took 5 hours or 15 hours
>?
>I'm trying to see how fast an algorithm is compared to others and I'm
>not
>sure what the standard is.  I'm on fedora 16.0 and using R 2.15.
>Thanks.
>
>	[[alternative HTML version deleted]]
>
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