[R] R_DirtyImage and Rprof

[Benjamin Tyner]

Hello,

I have some code which was running in interactive mode while Rprof(..., 
line.profiling = TRUE). Near the end of my script, it opens up a 
pipe(..., open = "w") to a perl script, and at that point the execution 
gets stuck using 100% cpu.

(The perl script itself never showed up in pstree, as far as I can tell).

I did a "tail -f" on the file being written to by Rprof, and it was 
reporting "sys.save.image" over and over, and in fact an ".RData" file 
appeared when I had not asked for one, and I was able to load it later.

This got me curious, as nowhere in my code do I directly use that 
function. Looking through the source code for R, it appears that 
"sys.save.image" is called whenever an R_DirtyImage condition is triggered.

This was using R version 3.2.2 under RHEL. My efforts to create a 
reproducible example of this behavior have thus far been unsuccessful.

My questions: is there any documentation for R_DirtyImage, and how 
plausible is it that the R_DirtyImage condition was triggered by 
something Rprof did? The reason for my conjecture is that 
sys.save.image() calls closeAllConnections(), which I imagine might have 
interfered with the pipe that was open for writing, thus causing the 
stuck execution at that point.

If so, any advice for avoiding the R_DirtyImage condition while profiling?

If not, any conjectures for what might actually be going on? For what 
it's worth, I have observed a similar situation when using Rprof + 
system() instead of pipe(); for example:

    https://stat.ethz.ch/pipermail/r-help/2015-August/431286.html

Regards
Ben