How to interrupt an R process that hangs

Hi all,

Thanks Simon and Duncan for the help. Sorry to be dense, but I'm still
unsure how to interrupt such processes. Here's an example:

for (i in 1:100000){
	a <- matrix(rnorm(100000*100000),ncol=100000)
	b <- svd(a)	}

If you run this,

R will hang (i.e., it's a legitimate execution, it
will just take a really long time to execute). The most obvious
solution is to write code that doesn't do unintended things, but
that's not always possible. Is there a way to interrupt it? I tried:

kill -s INT <PID>

and at least on Mac it had no effect.

On Mon, Mar 15, 2010 at 1:19 PM, Simon Urbanek
<simon.urbanek at r-project.org> wrote:

On Mar 15, 2010, at 14:42 , Adam D. I. Kramer wrote:

+1--this is the single most-annoying issue with R that I know of.

My usual solution, after accomplishing nothing as R spins idly for a
couple
hours, is to kill the process and lose any un-saved work.   
save.history()
is
my friend, but is a big delay when you work with big data sets as  
I do, so
I
don't run it after every command.

I have cc'd r-help here, however, because I experience this  
problem with
non-OSX R as well...when I run it in Linux or from the OSX command- 
line (I
compile R for Darwin without aqua/R-framework), the same thing  
happens.

Is there some way around this? Is this a known problem?

"Hanging" for a long period of time is usually caused by poorly  
written
C/Fortran code. You can always interrupt R as long as it is in the  
R code.
Once you load a package that uses native code (C/Fortran/..) you  
have to
rely on the sanity of the developer to call R_CheckUserInterrupt() or
rchkusr() often enough (see 6.12 in R-ext). If you have some  
particular
package that does not do that, I would suggest alerting the author.  
By
definition this requires cooperation from authors, because  
interrupting
random code forcefully (as it was possible many years ago) creates  
leaks and
unstable states.

Cheers,
Simon

Google searching suggests no solution, timeline, or anything, but  
the
problem has been annoying users for at least twelve years:
http://tolstoy.newcastle.edu.au/R/help/9704/0151.html

Cordially,
Adam

On Mon, 15 Mar 2010, Matthew Keller wrote:

HI all,

Apologies for this question. I'm sure it's been asked many times,  
but
despite 20 minutes of looking, I can't find the answer. I never use
the GUI, I use emacs, but my postdoc does, so I don't know what to
tell her about the following:

Occasionally she'll mess up in her code and cause R to hang
indefinitely (e.g., R is trying to do something that will take  
days).
In these situations, is there an option other than killing R (and  
the
work you've done on your script to that point)?

Thank you,

Matthew Keller


--
Matthew C Keller
Asst. Professor of Psychology
University of Colorado at Boulder
www.matthewckeller.com

-- 
Matthew C Keller
Asst. Professor of Psychology
University of Colorado at Boulder
www.matthewckeller.com