[R] (performance) time in Windows vs Linux

[Patrick Connolly]

On Mon, 29-Jun-2009 at 09:05AM +0200, Zeljko Vrba wrote:

|> On Mon, Jun 29, 2009 at 06:56:55PM +1200, Patrick Connolly wrote:
|> > On Mon, 29-Jun-2009 at 02:13AM -0400, milton ruser wrote:
|> > 
|> > |> Really?
|> > |> 
|> > |> In fact I have a quadcore. But how can I know if Linux are really
|> > |> using only one core, and how can I setup it to use the 4cores?
|> > 
|> > I use GKrellM (install with "aptitude install gkrellm" if you don't
|> > have it already).  It shows a trace of the % activity for each CPU
|> > where it's very clear if only one is being used.  I've never had
|> > occasion to change such a setting, but someone more skilled in such
|> > things could say how to make it use more than one.
|> > 
|> How do you know that it is *R* that uses all 4 CPUs, and not other
|> applications on the system?  What does running "top" in the
|> terminal say?  If R uses more than one CPU, it's CPU usage will be
|> > 100%.

There are undoubtedly more scientific ways, but if the machine is idling
with both krells showing a very low number like 2% BEFORE running the
R script, and then we see only one suddenly become 99 or 100%, it's a
fairly safe bet that it was R that made the difference -- particularly
if it drops back once the R code finishes.

I think top adds the two usages together, so values over 100% would be
possible.  The numbers shown by GKrellM could be thought of as more
sensible where you have the choice of composite, real or both.

HTH

-- 
~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.~.   
   ___    Patrick Connolly   
 {~._.~}                   Great minds discuss ideas    
 _( Y )_  	         Average minds discuss events 
(:_~*~_:)                  Small minds discuss people  
 (_)-(_)  	                      ..... Eleanor Roosevelt
	  
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