[R] RAM usage
ripley at stats.ox.ac.uk
Mon Oct 21 15:02:49 CEST 2002
On Mon, 21 Oct 2002, Vaidotas Zemlys wrote:
> >> I'm having problems while working with large data sets with R 1.5.1 in
> >> windows 2000. Given a integer matrix size of 30 columns and 15000 rows
> >> my function should return a boolean matrix size of about 5000 rows and
> >> 15000 columns.
> >That's 75million items of 4bytes each, hence almost 300Mb for that one
> Does that mean that R reserves 4 bytes for logical object with length 1? On
> the whole how much memory R allocates for different data types? I searched
R uses C integers, which are almost always 4 bytes. Fortran does
for logicals usually, for example, and that's probably why S did. It's
quite hard to work with smaller types in a portable way. (char need not
be 1 byte, for example.)
A logical vector of length 1 needs a lot more than 4 bytes, but one of
length 1e5 will be close to 4e5 bytes (unless it has names). There's
overhead and lignment issues to consider.
> a bit, but I didn't find anything useful on this subject. I would like to
> know if it is possible how much memory R needs for storing for example real
> matrix size of 50 rows and 100 columns together with column and row names.
> Or where to find information on such subject.
In the source files. reals are stored in the system's C double type,
which is usually 4 bytes.
> I thought that R needs only 1 byte for storing logical byte, and because of
> that I underestimated the size of memory R would need to use.
> > You have not told us your problem, so has not demonstrated that
> > `a lot of memory must be used'. Hard to help when we don't know what
> > you are attempting, but few problems cannot be done in pieces
> I did not tell my problem, because I thought that it was more or less
> irrelevant to the memory usage problems I was experiencing. My intention
> was to ask about how R manages memory and is there something special about
> that management everyone should know, but I don't know. I'm sorry if my
> letter was a bit unclear, English is not my native language.
But you did claim `must be used'. That really is rarely the case, and the
skill in programming R (or S) is use memory within the resources
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 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !) To: r-help-request at stat.math.ethz.ch
More information about the R-help