[Rd] Running two R instances at the same time

[Peter Juhasz]

On Mon, Sep 7, 2009 at 4:47 PM, Andrew Piskorski<atp at piskorski.com> wrote:
> On Sat, Sep 05, 2009 at 08:31:18PM +0200, Peter Juhasz wrote:
>
>> 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?
>
> No.  Particularly since there is no R "backend" involved at all, not
> if you're starting up the standard R from Ubuntu 9.04 (rather than
> Rserve or something else unusual).  People run multiple R processes
> concurrently on the same (multi-core) machine all the time, works
> fine.
>
>> 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.
>
> The most likely explanation seems to be that you have a bug in your
> Perl code.  Have you tried using your Perl framework to fork something
> OTHER than R?  Have you tried manually starting up two R processes and
> running your R code that way?  And, what is the actual R code you're
> running?  You don't seem to have shown it anywhere.
>
> --
> Andrew Piskorski <atp at piskorski.com>
> http://www.piskorski.com/
>

Actually, I have ran some tests that clarified the issue somewhat.

- It is always possible that my Perl code is buggy but that doesn't
seem to play a role in this case.
- I tried to use my Perl system to start two non-R processes - it
worked as expected, they ran concurrently without ill effects.

But please see http://www.perlmonks.org/index.pl?node_id=793907 ,
where I posted my R code in its simplest form along with an example
run which exhibits the symptoms I originally wrote about.

>From that test I conclude that it is not my Perl code nor R itself
that is wrong here, but the specific package I use. That package -
NADA, from which I use the 'cenros' command - seems to be the culprit.

Please forgive my complete lack of experience when it comes to R, this
made me assume things that didn't make sense.

Péter Juhász