SO what could possibly be causing this? Has anyone encountered this? This
is RedHat Enterprise 5.7.


On Tue, Aug 27, 2013 at 11:14 PM, Prof Brian Ripley
<ripley@stats.ox.ac.uk>wrote:

> On 28/08/2013 06:54, joe meiring wrote:
>
>> This does speed up on an OsX install, so something must be wacky with the
>> linux install. Any ideas as to what would cause this?
>>
>
> It does on a Linux platform ('install' has nothing to do with this):
>
> > system.time(x <- lapply(test,function(x) loess.smooth(x,x)))
>    user  system elapsed
>   4.095   0.036   4.140
>
> > system.time(x <- mclapply(test,function(x) loess.smooth(x,x),
> mc.cores=24))
>    user  system elapsed
>   8.125   0.639   0.563
>
> What is odd is that no CPU time is being recorded in the original posting.
>
> That is about what I would expect: there is an overhead in forking 24
> processes and this example is too small to be realistic.
>
>
>> On Tuesday, August 27, 2013 4:19:31 PM UTC-7, joe meiring wrote:
>>
>>>
>>> I can't seem to get mclapply to use more than a single core. I have a 64
>>> core server running Linux.
>>>
>>> Fore example:
>>>
>>> library(parallel)
>>>
>>> test <- lapply(1:100,function(x) rnorm(10000))
>>> system.time(x <- lapply(test,function(x) loess.smooth(x,x)))
>>> system.time(x <- mclapply(test,function(x) loess.smooth(x,x),
>>> mc.cores=32))
>>>
>>> gives me:
>>>
>>>     user  system elapsed
>>>    0.000   0.000   7.441
>>>     user  system elapsed
>>>    0.000   0.000   8.868
>>>
>>> i.e. mclapply is taking longer than lapply(). What is going wrong here?
>>>
>>>          [[alternative HTML version deleted]]
>>>
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>>
>
> --
> Brian D. Ripley,                  ripley@stats.ox.ac.uk
> Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~**ripley/<http://www.stats.ox.ac.uk/~ripley/>
> University of Oxford,             Tel:  +44 1865 272861 (self)
> 1 South Parks Road,                     +44 1865 272866 (PA)
> Oxford OX1 3TG, UK                Fax:  +44 1865 272595
>
> ______________________________**________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help>
> PLEASE do read the posting guide http://www.R-project.org/**
> posting-guide.html <http://www.R-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>

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