Running R on dual/quad Opteron machines

The environment will probably be either Unix/Linux or Solaris and the
amount of RAM will be 8-16Gb, depending on the number of processors.
My main concerns are the following:

1. How much does R  benefit from passing from one processor to
two/four processor machines? Consider that the typical intensive use
of the server
will be represented by simulation studies with many repeated loops.

The typical way that R is used on multiprocessor systems is running more 
than one program, rather than parallel processing. If four people are 
using the computer or if one person splits 10,000 iterations of a 
simulation into 4 sets of 2,500 you will be using all four processors.

2. How does R cope with parallelization and/or parallelized compiled code ?

It doesn't really.  There are interfaces to MPI and PVM and there is the 
possibility of using a parallel BLAS to speed up linear algebra.  These 
won't help much unless the server is under fairly low load so that a 
single program can use more than 100% of a single processor.  Our 
multiprocessor Opteron servers are rarely that underutilized.

 	-thomas

Thomas Lumley			Assoc. Professor, Biostatistics
tlumley at u.washington.edu	University of Washington, Seattle