[R] getting faster results

[Liaw, Andy]

It can depend on a whole list of things why the computations were taking so
long, and just saying what methods you are using to do the computation is
far from sufficient, as there are efficient ways and inefficient ways to do
any computations, and we don't know how you did any of them.  With the
little information you gave, you cannot honestly expect much help.  All
anyone can give you is generic advise.  Mine is as follows:\

- R has profiling facility that tells you what part(s) of the computation is
taking the most time.  Use it.  (See ?Rprof.)

- If you see (or hear) lots of disk activity, but fairly low CPU usage, you
might be short in physical memory, and R is using virtual memory, which will
be _very_ slow.

- Given the same hardware, there's little difference in performance between
different OSes, although Linux seems to have an edge.  Compilers used can
also make a difference. 

- Hardware can make a large difference.  On some analyses I did, running the
same code on an Opteron box running 64-bit Linux (SLES) was over six times
faster than on my Pentium M laptop.

Andy

From: Elizabeth Lawson
> 
> I am running algorithms for Bayesian hierarchical models with 
> 20 or more variables or writing alogrithms that solve for 
> partially linear models using wavlelet estimation.  Soemtimes 
> just creating the predicted vaules from the Bayesian analysis 
> takes over a day to run!
>   I am just wondering if R runs faster on any particular 
> systems or if it is about the same regardless.
> 
> jim holtman <jholtman at gmail.com> wrote:
>   Need to know what you are trying to do with the data.  
> Depending on what you want to do and how you do it will 
> determine the speed.  I can take a dataframe with 1,000,000 
> rows of transaction data and compute the average and plot a 
> histogram of the response time in less that a couple of 
> seconds.  Is that fast enough? 
> 
>   On 12/13/05, Elizabeth Lawson <lizzylaws at yahoo.com> wrote:   Hey,
> 
> Can anyone answer this question.  I am working with really 
> large datasets and most of the programs I have been running 
> take quite some time. 
> 
> I heard that R may be faster in Unix.  I sthis true and if so 
> can anyone reccomend which system and requirements may allow 
> things to go faster for?
> 
> Thanks!!
> 
> Elizabeth Lawson
> 
> 
> --------------------------------- 
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> 
> -- 
> Jim 
> Holtman
> Cincinnati, OH
> +1 513 247 0281
> 
> What the problem you are trying to solve?   
> 
> 
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