From ripley at stats.ox.ac.uk  Tue Mar  7 10:15:53 2006
From: ripley at stats.ox.ac.uk (Prof Brian Ripley)
Date: Tue, 7 Mar 2006 09:15:53 +0000 (GMT)
Subject: [Rd] Running R on dual/quad Opteron machines
In-Reply-To: <3c12769c0603070059kfa51d68h8c2da372beecef29@mail.gmail.com>
References: <Pine.LNX.4.64.0603061035570.17097@homer23.u.washington.edu>
	<C031F78E.7745%sdavis2@mail.nih.gov>
	<3c12769c0603070059kfa51d68h8c2da372beecef29@mail.gmail.com>
Message-ID: <Pine.LNX.4.64.0603070907380.12003@gannet.stats.ox.ac.uk>

On Tue, 7 Mar 2006, Simone Giannerini wrote:

> Ok thanks, I am wondering whether running multiple instances of R
> would be possible without problems in presence of compiled code
> (shared libraries).
> Intuitively, while there can be multiple instances of R, all of them
> would be using the same library, but I am just guessing, I might do a
> check on this.

That's what the `shared library' means.  The common parts (e.g. code and 
static data) are shared, but the data areas are not.

Different processes run in different address spaces, and modern OSes are 
careful only to give a user process write access to its own address space.

Many of us have servers running multiple copies of R at almost all times.
I typically run R tests with four copies running on a dual-CPU Opteron, 
that being about the minimum number needed to get 100% CPU usage since I/O 
is also being done.

>
> Ciao
>
> Simone
>
>>
>> And let me couch my earlier statements on snow/Rmpi by saying that we use
>> these tools on a relatively large beowulf cluster (~200 nodes), which is
>> somewhat different than a single box with 2-4 processors, so it is may not
>> be worth the trouble outside of a cluster environment.  For example, we have
>> not moved to using Rmpi/snow on our dual-processor G5s because the speed
>> gain just isn't worth the extra installation trouble, etc.
>>
>> Sean

-- 
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)
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[Rd] Running R on dual/quad Opteron machines
Prof Brian Ripley