Single vs. dual CPUs

"Milton Lopez" <mlopez at iattc.org> writes:

I've posted this earlier and have not heard much so far. I'd really appreciate any guidance on this as we are about to order new hardware.

We are buying Dell workstations with Red Hat Linux and 64-bit Xeon
CPUs to run R. We could add a second processor to each system, or
buy slightly faster single CPU systems. Is it possible to make a
generalized statement as to what kind of performance improvement we
would see with a single vs. dual processors when running R on these
systems?

Well, if you ask that way, the answer is probably no...

It depends on the usage pattern. If you run multiple CPU-bound
processes in parallel without too much coordination (parallel make is
a good example, simulations another), then you get close to double up
from a dual. For a single R process, you can get something like 40%
improvement in large linear algebra problems, using a threaded ATLAS.
For other problems the speedup is basically nil. There is some
potential in threading R or (much easier) some of its vector
operations, but that is not even on the drawing board at this stage.

Also, these days you might want to consider another factor: noise.
Duals tend to be server machines with little emphasis on quietness,
where the single-CPU machines have heatpipes and whatnot.

O__  ---- Peter Dalgaard             ?ster Farimagsgade 5, Entr.B
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