On 05/29/2012 08:02 PM, Fabrice Tourre wrote:
Dear list,
I want to run two independent calculation (A, B) and then combined
their results to do a plot in R. Before I just run calculation A
first, then calculation B. It will take some times. I just have one
server with multiple core. I noticed that there are some nice package
in R for parallel calculation, such as parallel, multicore and snow.
Also there is a book, O’Reilly – “Parallel R, Data Analysis in the
Distributed World” book by Q. Ethan McCallum and Stephen Weston.
When track into these packages, I am a little of lost because I did
not know parallel calculation too much.
Could any one can give me some example codes for my purpose? So I can
easy follow.
Here we sleep for 20 seconds, but do it in only 5 seconds!
> library(parallel)
> system.time(mclapply(1:4, function(i) Sys.sleep(5), mc.cores=4))
user system elapsed
0.006 0.025 5.021
Often, it is possible to use mclapply just like lapply; use the
'parallel' library, and for single processor machines the mclapply and
similar functions rather than parLapply and similar. This
vignette("parallel", package="parallel")
might provide further help. Likely you will get benefit from making your
calculation A use parallel calculations, and B use parallel calculation.
Martin
Thank you very much in advance.
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