Re: [R] system.time

From: Prof Brian Ripley (ripley@stats.ox.ac.uk)
Date: Mon 23 Jul 2001 - 22:59:31 EST

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Message-id: <Pine.LNX.4.31.0107231353360.13314-100000@gannet.stats>

On Mon, 23 Jul 2001, Agustin Lobo wrote:

>
> The manual entry for system.time refers to
> "user, system, and total elapsed times for the currently running R
> process".
>
> Is user time the time spent by the process itself and system time the
> time spent on other system activities?

These are reported by your (presumably Unix?) system. Most likely both
times are spent by the R process, the `user' time in the user code space,
and the `system' time in kernel calls.

Look up the times system call on your system for the exact details.
For example, Solaris says

     The tms_utime member is the CPU time used while executing
     instructions in the user space of the calling process.

     The tms_stime member is the CPU time used by the system on
     behalf of the calling process.

On Unix-alikes, system.time calls proc.time whose C code calls times.

-- 
Brian D. Ripley,                  ripley@stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595
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