On 03.08.2012 19:21, Xavier Portell/UPC wrote:
Hi everyone,
I'm aiming to run an external executable (say filetorun.EXE) in parallel. The external executable collect needed data from a
file, say "input.txt" and, in turn,generates several output files, say "output.txt". I need to generate
"input.txt", run the executable and keep "input.txt" and "output.txt". I'm using Windows 7, R
version 2.15.1 (2012-06-22) on RStudio and platform: i386.pc.mingw32/i386 (32-bit).
My first attempt was a R code which, by using
System("filetorun.EXE", intern = F, ignore.stdout = F,
ignore.stderr = F, wait = T, input = NULL,
show.output.on.console = T, minimized = F, invisible = T))
, ran the executable and kept required files to a conveniently named folder.
After that I changed my previous R script so I could use the function
lapply().This script apparently worked fine.
Finally, I tried to parallelize the problem by using snow and parLapply(). The
resulting script looks like this:
## Not run
#
library(snow)cl <- makeCluster(3, type = "SOCK")
clusterExport(cl,list('param.esp','copy.files','for12.template','program.executor'))
parLapply(cl,a.list,a.function))stopCluster(cl)
#
##End not run
Although it runs, the parallelized version is messing up the input parameters to pass to the
executable (see table below, where parameters P1 and P2 are considered. ".s" comes from
the serial code and ".p" from the parallelized one):
s r P1.s P2.s P1.p P2.p
1 1 1 1.0 3.00 2.0 3.00
2 2 1 1.5 3.00 2.0 3.75
3 3 1 2.0 3.00 2.0 3.00
4 4 1 1.0 3.75 1.5 3.00
5 5 1 1.5 3.75 1.5 3.00
6 6 1 2.0 3.75 2.0 3.75
My first thought to avoid the described behaviour was creating a temporary file, say "tmp.id" with id being an identification run number,
and copying "filetorun.EXE" and "Input.txt" to "tmp.id". However, while doing so, I realised that although running the
correct "filetorun.EXE" copy (i.e., the one in "tmp.id") R looks for "input.txt" in the work directory.
Not sure about the real setup, but you can actually specify the path,
not only filenames.
Uwe Ligges
I've been looking thoroughly for a solution but I got nothing.
Thanks for any help in advance,
Xavier Portell Canal
PhD candidate
Department of Agri-food engineering,
Universitat Politècnica de Catalunya
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and provide commented, minimal, self-contained, reproducible code.
