[Rd] mcmapply Core Usage

[Simon Urbanek]

On May 29, 2014, at 8:04 PM, Henric Winell <nilsson.henric at gmail.com> wrote:

> Simon Urbanek skrev 2014-05-29 15:06:
>> Dario,
>> 
>> yes, that is a bug, now fixed.
> 
> Thanks for fixing it.
> 
> This problem was independently reported some time ago (https://bugs.r-project.org/bugzilla/show_bug.cgi?id=15016) and I believe that it can now be closed.
> 

Ah, thanks, done,
Simon


> 
>> 
>> Cheers,
>> Simon
>> 
>> 
>> On May 29, 2014, at 2:00 AM, Dario Strbenac <dstr7320 at uni.sydney.edu.au> wrote:
>> 
>>> Hello,
>>> 
>>> I have a minimal example that shows a problem I'm having with parallel processing.
>>> 
>>> library(parallel)
>>> mcmapply(function(x, y)
>>> {
>>>  print("Running")
>>>  Sys.sleep(10)
>>> }, as.list(1:10), as.list(10:1), mc.cores = 16, SIMPLIFY = FALSE)
>>> 
>>> I see "Running" printed once every ten seconds. I read the documentation for mcmapply, but I don't understand why it wouldn't print all ten output statements almost at once, then wait for about ten seconds, then return to the prompt. Is it documented in another location ?
>>> 
>>> My problem is that I have a section of code that takes a long time, which I have replaced with Sys.sleep in the above example, but when I look at the output of top, I only see 1 CPU being used. The computer has 16 processors.
>>> 
>>>> sessionInfo()
>>> R version 3.1.0 (2014-04-10)
>>> Platform: x86_64-pc-linux-gnu (64-bit)
>>> 
>>> locale:
>>> [1] LC_CTYPE=en_AU.UTF-8       LC_NUMERIC=C
>>> [3] LC_TIME=en_AU.UTF-8        LC_COLLATE=en_AU.UTF-8
>>> [5] LC_MONETARY=en_AU.UTF-8    LC_MESSAGES=en_AU.UTF-8
>>> [7] LC_PAPER=en_AU.UTF-8       LC_NAME=C
>>> [9] LC_ADDRESS=C               LC_TELEPHONE=C
>>> [11] LC_MEASUREMENT=en_AU.UTF-8 LC_IDENTIFICATION=C
>>> 
>>> attached base packages:
>>> [1] parallel  stats     graphics  grDevices utils     datasets  methods
>>> [8] base
>>> 
>>> loaded via a namespace (and not attached):
>>> [1] tools_3.1.0
>>> 
>>> --------------------------------------
>>> Dario Strbenac
>>> PhD Student
>>> University of Sydney
>>> Camperdown NSW 2050
>>> Australia
>>> 
>>> ______________________________________________
>>> R-devel at r-project.org mailing list
>>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>> 
>> 
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