[R] Memory in R on windows running 64bit XP

[Duncan Murdoch]

On 9/16/2009 10:16 AM, michael watson (IAH-C) wrote:
> Hi
> I'm running 32-bit R on Windows XP 64bit and the machine has 16Gb of RAM. The help for memory.limit states:
> 
> If 32-bit R is run on some 64-bit versions of Windows the maximum value of obtainable memory is just under 4GB.
> 
> So, using the help which states the size parameter can go up to 4095:
> 
> memory.limit(size=4095)
> 
> When I run mclust I get:
> 
> Error: cannot allocate vector of size 1.3 Gb
> 
> So, now I set the max-mem-size flag:
> 
> --max-mem-size=3500M
> 
> Repeat and I still get the same error:
> 
> Error: cannot allocate vector of size 1.3 Gb
> 
> So, can anyone help?  32 bit R is reported to be able to use up to 4Gb of RAM on 64 bit windows, yet mine croaks at 1.3Gb.

You are misreading things in a couple of places.  The most important one 
is the error message: it says allocation of a 1.3 Gb object failed.  You 
may have 4 Gb available in total, but have used so much of it already 
that Windows won't allocate a 1.3 Gb piece to R.  Using Rprofmem() might 
show how the allocations are happening.

Another possibility is that your particular version of Windows doesn't 
support giving 4 Gb to R.  Run memory.size(NA) to find out the limit, 
memory.size() to find out the current amount in use.

And even if the limit is close to 4 Gb and you have more than 1.3 Gb 
free, the allocation may fail because there is no sufficiently large 
contiguous block available.  Once memory is allocated, that address is 
in use and is unavailable.  Since the 32 bit address space only covers 4 
Gb, you can fairly easily end up with allocations that are spread out 
across it leaving no large blocks available.  That's the advantage of 
switching to 64 bit R:  even if you still only had 4 Gb of memory 
available, the address space is so much bigger that fragmentation 
probably won't be a problem.

Duncan Murdoch

> 
>> sessionInfo()
> R version 2.9.2 (2009-08-24)
> i386-pc-mingw32
> locale:
> LC_COLLATE=English_United Kingdom.1252;LC_CTYPE=English_United Kingdom.1252;LC_MONETARY=English_United Kingdom.1252;LC_NUMERIC=C;LC_TIME=English_United Kingdom.1252
> attached base packages:
> [1] stats     graphics  grDevices utils     datasets  methods   base
> other attached packages:
> [1] mclust_3.3.1
> 
> Thanks
> Mick
> 
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