[Rd] Memory management problem?
Prof Brian D Ripley
Tue, 12 Jun 2001 19:16:55 +0100 (GMT Daylight Time)
On Tue, 12 Jun 2001 firstname.lastname@example.org wrote:
> I just ran into the following problem. I am not sure what causes it, but
> here is the scenario:
> (1) I start R with 512Mb of memory. (I am on an Win2000 PC with 512Mb of
> physical memory)
> (2) I put a couple of small functions in my workspace and I generate two
> real vectors x and y of length 2^19 (542288) each.
> (3) I save this workspace. The size of the saved file is about 8.4Mb.
> (4) I run lm to fit y vs. x using an 11 parameter model. I generate a
> couple of plots. Everything is fine. (BTW, this runs out of memory with
> standard 256Mb allocation of maximum memory).
> (5) I regenerate y (it is a simulated example) overwriting the old one.
> (6) I run (4) again and I am getting:
> Error: cannot allocate vector of size 45056kb
> Reached total allocation of 512Mb
> This happens even if I run gc() after (5).
> (7) Now comes an interesting part. If I save the image right now the size
> of it is about 159Mb although I do not have any new objects in my workspace
> (there is a hidden object .Trace, but it is small).
> (8) If I do
> rm(list=ls(pos=1), pos=1)
> however, the size of the workspace comes back to almost zero.
> I am not sure if this happens on Linux since my Linux box only has 192Mb of
> Is this the new memory management problem? Is there any way around it?
No, it's an old one, called fragmentation, I expect. There may be no
free space of size 45Mb, and remember R no longer moves objects. Also,
the allocation over 256Mb may well be fragmented.
I think you have the solution already: remove objects you are no longer
Brian D. Ripley, email@example.com
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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