[R] Running two R instances at the same time

[Jim Holtman]

if I look at your output, the single thread is using almost 100% of  
the two cpus (3:49 real, 5:49 user or something close to that).  for  
the two thread case it is close to the same with the user now  
something like 6:15.  I would like to see what the contribution of  
each of the processes are.  put some proc. time calls in the R script  
to see what it is using.

Sent from my iPhone

On Sep 5, 2009, at 7:21, Peter Juhasz <peter.juhasz83 at gmail.com> wrote:

> Dear R experts,
>
> please excuse me for writing to the mailing list without subscribing.
> I have a somewhat urgent problem that relates to R.
>
> I have to process large amounts of data with R - I'm in an
> international collaboration and the data processing protocol is fixed,
> that is a specific set of R commands has to be used.
>
> I wrote a perl program that manages creation of data subsets from my
> database and feeds these subsets to an R process via pipes.
>
> This worked all right, however, I wanted to speed things up by
> exploiting the fact that I have a dual-core machine. So I rewrote my
> perl driver program to use two threads, each starting its own R
> instance, getting data off a queue and feeding it to its R process.
>
> This also worked, except that I noticed something very peculiar: the
> processing time was almost exactly the same for both cases. I did some
> tests to look at this, and it seems that R needs twice the time to do
> the exact same thing if there are two instances of it running.
>
> I don't understand how is this possible. Maybe there is an issue of
> thread-safety with the R backend, meaning that the two R *interpreter*
> instances are talking to the same backend that's capable of processing
> only one thing at a time?
>
> Technical details: OS was Ubuntu 9.04 running on a Core2Dou E7300, and
> the R version used was the default one from the Ubuntu repository.
>
> Please see http://www.perlmonks.org/?node_id=792460 for an extended
> discussion of the problem, and especially
> http://www.perlmonks.org/?node_id=793506 for excerpts of output and
> actual code.
>
> Thanks for your answers in advance:
> Péter Juhász
>
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