[Rd] mcmapply Core Usage

[Henric Winell]

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.

Henric


>
> 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
>>
>
> ______________________________________________
> R-devel at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
>