[R] Parallel computing on Windows (foreach)

[Mario Valle]

On 15-Jun-10 17:07, Sergey Goriatchev wrote:
> Hello,
>
> I am reading "Using The foreach Package" document and I have tried the
> following:
>
> ---------------------------------------------------------------------
>
>> sessionInfo()
> R version 2.10.1 (2009-12-14)
> i386-pc-mingw32
>
> locale:
> [1] LC_COLLATE=German_Switzerland.1252
> LC_CTYPE=German_Switzerland.1252
> LC_MONETARY=German_Switzerland.1252 LC_NUMERIC=C
>   LC_TIME=German_Switzerland.1252
>
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
>
> other attached packages:
> [1] foreach_1.3.0   codetools_0.2-2 iterators_1.0.3
>
>
>> x<- numeric(10000)
>> system.time(for(i in 1:10000) x[i]<- sqrt(i))
>     user  system elapsed
>     0.03    0.00    0.03
>>
>> system.time(system.time(x<- foreach(i=1:10000, .combine="c") %do% sqrt(i)))
>     user  system elapsed
>     7.14    0.00    7.14
>>
>> system.time(system.time(x<- foreach(i=1:10000, .combine="c") %dopar% sqrt(i)))
>     user  system elapsed
>     7.19    0.00    7.19
> Warning message:
> executing %dopar% sequentially: no parallel backend registered
>
> ------------------------------------------------------------------------
>
> Not only is the sequential foreach much slower than the simple
> for-loop (as least in this particular instance), but I am not quite
> sure how to make foreach run parallel. Where would I get this parallel
> backend?

Use doMPI and run R through mpirun (for example run on 8 cores):

mpirun -np 8 R --slave -f your-script.r

Hope it helps
		mario



I looked at doMC and doRedis, but these do not run on
> Windows, as far as I understand. And doSNOW is something to use when
> you have a cluster, while I have a simple dual-core PC.
>
> It is not really clear for how to make parallel computing work. Please, help.
>
> Regards,
> Sergey
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

-- 
Ing. Mario Valle
Data Analysis and Visualization Group            | 
http://www.cscs.ch/~mvalle
Swiss National Supercomputing Centre (CSCS)      | Tel:  +41 (91) 610.82.60
v. Cantonale Galleria 2, 6928 Manno, Switzerland | Fax:  +41 (91) 610.82.82