Running R on dual/quad Opteron machines
On 3/6/06 1:37 PM, "Thomas Lumley" <tlumley at u.washington.edu> wrote:
On Mon, 6 Mar 2006, Simone Giannerini wrote:
On 3/6/06, Thomas Lumley <tlumley at u.washington.edu> wrote:
On Mon, 6 Mar 2006, Simone Giannerini wrote:
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.
Many thanks, if I have understood correctly, in this case I would need running four separate instances of R, since a single thread cannot exploit more than one cpu, am I correct?
You *can* exploit more than one CPU using eg the "snow" package, but it's often easier to just run multiple instances of R, and for a shared computing system there are often multiple people each running one instance of R.
And let me couch my earlier statements on snow/Rmpi by saying that we use these tools on a relatively large beowulf cluster (~200 nodes), which is somewhat different than a single box with 2-4 processors, so it is may not be worth the trouble outside of a cluster environment. For example, we have not moved to using Rmpi/snow on our dual-processor G5s because the speed gain just isn't worth the extra installation trouble, etc. Sean