Re: [R] Memory Management under Linux: Problems to allocate large amounts of data

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Thu 30 Jun 2005 - 17:43:32 EST

On Thu, 30 Jun 2005, Dubravko Dolic wrote:

> Dear Prof. Ripley.
>
> Thank You for Your quick answer. Your right by assuming that we run R on
> a 32bit System. My technician tried to install R on a emulated 64bit
> Opteron machine which led into some trouble. Maybe because the Opteron
> includes a 32bit Processor which emulates 64bit (AMD64 x86_64). As You
> seem to have good experience with running R on a 64bit OS I feel
> encouraged to have another try for this.

It should work out of the box on an Opteron Linux systen: it does for example on FC3 and SuSE 9.x. Some earlier Linux distros for x86_64 are not fully 64-bit, but we ran R on FC2 (although some packages could not be installed).

Trying to build a 32-bit version of R on FC3 does not work for me: the wrong libgcc_s is found. (One might want a 32-bit version for speed on small tasks.)

> -----Ursprüngliche Nachricht-----
> Von: Prof Brian Ripley [mailto:ripley@stats.ox.ac.uk]
> Gesendet: Mittwoch, 29. Juni 2005 15:18
> An: Dubravko Dolic
> Cc: r-help@stat.math.ethz.ch
> Betreff: Re: [R] Memory Management under Linux: Problems to allocate large amounts of data
>
> Let's assume this is a 32-bit Xeon and a 32-bit OS (there are
> 64-bit-capable Xeons). Then a user process like R gets a 4GB address
> space, 1GB of which is reserved for the kernel. So R has a 3GB address
> space, and it is trying to allocate a 2GB contigous chunk. Because of
> memory fragmentation that is quite unlikely to succeed.
>
> We run 64-bit OSes on all our machines with 2GB or more RAM, for this
> reason.

-- 
Brian D. Ripley,                  ripley@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

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Received on Thu Jun 30 17:47:15 2005

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