[R] vsize and nsize

Prof Brian D Ripley ripley at stats.ox.ac.uk
Sat May 15 09:12:38 CEST 1999

On Fri, 14 May 1999, Tony Long wrote:

> I am running R version ??? under Redhat 5.2.  It seems as though the
> --nsize object has no effct on the size of the allocated Ncells as
> determined using gc().  Yes, I have that much data....
> That is if I envoke R with
> R --vsize 100 --nsize 5000000
> then type
> gc()
> I get
> 	free		total
> Ncells	92202		200000
> Vcells	12928414	13107200

Well, we do need to know what ??? is (is it so hard?: it appears on the
start-up banner, or use Version()). There are limits to both nsize and
vsize, but they are currently 20000000 and 2048M.  If you try to specify
more than the limit, you will get a warning about the limit being ignored.
(Have you overlooked that as well as the start-up banner?) Given that a
recent version of R will object to --vsize 100 (it should be 100M), I
surmise yours is not 0.64.1 and suggest you upgrade.

The limits are OS-specific compile-time settings: look in src/unix/system.c
to change them for Linux. The real limit on vsize is LONG_MAX, slightly
greater on a 32-bit machine, and I guess the limit on nsize is chosen to be
comparable (it is harder to need lots of ncells).  However, as Ross has
said here, R is not designed for very large computations so the current
limits may be rather academic.

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

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