[R-SIG-Mac] Frozen script editor window while R console is computing

[Simon Urbanek]

On Mar 25, 2009, at 21:04 , Brant Inman wrote:

>
> R for MAC experts:
>
> When using the current version of R for MAC, I notice a troublesome  
> behavior.  Sometimes I need to build complex regression models  
> (usually using lmer) or simulations that take 10 minutes or more for  
> the computer to compute.  While this computing is going on, I would  
> like to be able to take advantage of this "free time" to write more  
> code.  But I can't! In my current setup of R for MACs the script  
> editor is frozen while the console is computing. That means that my  
> only recourse is to go for a 10 minute coffee or to the toilet.  I  
> don't believe that my windows version of R has this same problem.
>
> My question:  Is there a way to set R for MAC up so that the script  
> editor window is functional while the console window in chomping  
> away at some calculations?
>

The current GUI is running in the same event loop as R in order to  
allow R to use UI elements directly. This implies that if some C code  
in R hogs the CPU without allowing UI events to be processed, it will  
block the whole UI including the editor. "Good" packages won't do that  
since R provides R_CheckUserInterrupt() call to prevent this from  
happening, but apparently some still do.

Although there is a draft of a GUI that runs R on a separate thread  
from the GUI, but it opens up a whole can of worms since all access to  
system libraries needs to be scheduled on the main thread. Since R has  
no provision for that, it would make it likely that packages will  
violate this rule thus making R unstable, especially since it's OS- 
specific. Unfortunately UIs on OS X have to run on the main thread, so  
we cannot run R on the main thread and the GUI on a separate thread.  
Therefore the best we can currently do is to rely on packages to check  
events during long computations in C code. Note that this is not an  
issue in pure R code because R makes sure the check are done.

Cheers,
Simon