memory problem under windows

Did you read the *rest* of what the rw-FAQ says?

  Be aware though that Windows has (in most versions) a maximum amount of
  user virtual memory of 2Gb, and parts of this can be reserved by 
  processes but not used. The version of the memory manager used from R
  1.9.0 allocates large objects in their own memory areas and so is better
  able to make use of fragmented virtual memory than that used previously.

  R can be compiled to use a different memory manager which might be
  better at using large amounts of memory, but is substantially slower
  (making R several times slower on some tasks).

So, it tells you about memory fragmentation, and it tells you about making 
R aware of large-memory versions of Windows and that an alternative memory 
manager can be used.  If you actually tried those, the posting guide asks 
you to indicate it, so I presume you did not.

Also, take seriously the idea of using a more capable operating system 
that is better able to manage 2Gb of RAM.

I have (still) some memory problems, when trying to allocate a huge array:

WinXP pro, with 2G RAM

I start R by calling:	

Rgui.exe --max-mem-size=2Gb (as pointed out in R for windows FAQ)

R.Version(): i386-pc-mingw32, 9.1, 21.6.2004

## and here the problem
x.dim <- 46
y.dim <- 58
slices <- 40
volumes <- 1040
a <- rep(0, x.dim * y.dim * slices * volumes)
dim(a) <- c(x.dim, y.dim, slices, volumes)

gives me: "Error: cannot allocate vector of size 850425 Kb"

even though

memory.limit(size = NA)
yields 	2147483648

and

memory.size()
gives 905838768

so why is that and what can I do against it?

Many thanks for your kind help

Cheers

Christoph

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