[Rd] R's IO speed

[Vadim Ogranovich]

A technical question here: how does one measure the memory overhead
mentioned below? I have a set of functions of my own and would like to
profile them.

Thanks,
Vadim 

> -----Original Message-----
> From: r-devel-bounces at stat.math.ethz.ch 
> [mailto:r-devel-bounces at stat.math.ethz.ch] On Behalf Of Prof 
> Brian Ripley
> Sent: Sunday, December 26, 2004 2:04 AM
> To: R-devel at r-project.org
> Subject: [Rd] R's IO speed
> 
> R-devel now has some improved versions of read.table and write.table.
> 
> For a million-row data frame containing one number, one 
> factor with few levels and one logical column, a 56Mb object.
> 
> generating it takes 4.5 secs.
> 
> calling summary() on it takes 2.2 secs.
> 
> writing it takes 8 secs and an additional 10Mb.
> 
> saving it in .rda format takes 4 secs.
> 
> reading it naively takes 28 secs and an additional 240Mb
> 
> reading it carefully (using nrows, colClasses and 
> comment.char) takes 16 secs and an additional 150Mb (56Mb of 
> which is for the object read in).
> (The overhead of read.table over scan was about 2 secs, 
> mainly in the conversion back to a factor.)
> 
> loading from .rda format takes 3.4 secs.
> 
> [R 2.0.1 read in 23 secs using an additional 210Mb, and wrote 
> in 50 secs using an additional 450Mb.]
> 
> 
> Will Frank Harrell or someone else please explain to me a 
> real application 
> in which this is not fast enough?
> 
> -- 
> Brian D. Ripley,                  ripley at stats.ox.ac.uk
> Professor of Applied Statistics,  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
> 
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