Hi Brian,
Thank you for the clarification -- the first part does set the record
straight about what I thought about R. I would expect a program to run
on a single core by default unless something specifically (and somewhat
non-trivial) was done to it.
Prof Brian Ripley wrote:
If you want to check if R is running on more than one core, then
obviously R should appear more than once and with two different values
under CPU.
Not so: that will happen if multiple copies of R are running, not if a
single copy of R is running multiple threads.
Ah, yes, you are right -- there is a big difference. The former works
for both multiple copies of R or a single program [purposely not saying
"R" here to keep it general] running on multiple cores [distributed
memory parallelization]. It doesn't work for multiple threads, though.
(As an aside for anyone else interested, my Debian distribution has the
package "r-cran-rmpi", which is described as the "GNU R package
interfacing MPI libraries"...so that seems to be another way to use
multiple cores, though I have never used it...)
Ray
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