[R] Way to make R idle for some time and try something again later

[Prof Brian Ripley]

This depends on what else is going on.  My guess is that you are running 
the Aqua GUI, and it is servicing the GUI which is taking the time, not R 
itself.

On all of Linux, Solaris and Windows (RGui or Rterm) Sys.sleep() does use 
very close to zero resources at the beginning of a session, but things may 
be different if e.g. tcltk widgets are in use.

On Fri, 29 Jul 2005, Don MacQueen wrote:

> I done something very similar -- have R watch a file, and whenever
> new data is added to the file, read the new data from the file. In my
> case, new data was arriving once per minute, so I needed to have R
> wait about a minute before looking for new data.
>
> On my unix-based system, I found that if I usd

I don't think your system IS `unix-based' (Unix is a trademark, and MacOS 
X is based on a rather different kernel).  It is quite possible that it is 
behaving differently from the POSIX description of Unix system calls on 
which R is based for Unix-alikes.

>       Sys.sleep( N )
> then cpu usage immediately went up drastically. If the the system is
> otherwise fairly idle, cpu usage goes up to nearly 100%. A cpu
> monitor shows that R is using the cpu cycles.
>
> If I use instead
>      system('sleep N')
> cpu usage does not go up.

Does that freeze the GUI?  It certainly freezes tcltk widgets on Unix.

> (where N is the number of seconds to sleep)
>
>>  version
>          _
> platform powerpc-apple-darwin7.9.0
> arch     powerpc
> os       darwin7.9.0
> system   powerpc, darwin7.9.0
> status
> major    2
> minor    1.1
> year     2005
> month    06
> day      20
> language R
>
>
> At 12:13 PM -0700 7/29/05, Tae-Hoon Chung wrote:
>> Hi, All;
>>
>> I have a question. In R, what is the best way to make R idle for a while and
>> try something again later? For example, suppose there is an R job which
>> accesses a file that may be shared with other active jobs. So when the file
>> is being accessed by other job, your job will not be able to access the file
>> and your job will crash because of that. To avoid this, you want your job to
>> try to access the file repeatedly with some time interval, say every 10
>> seconds or something like that. Which is the best way to do this in R?


-- 
Brian D. Ripley,                  ripley at 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 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595