[R-pkg-devel] [Tagged] Re: multithreading in packages

 FWIW there is some machinery in the glmmTMB package for querying, setting, 
etc. the number of OpenMP threads.

https://github.com/glmmTMB/glmmTMB/search?q=omp

On 10/9/21 11:45 AM, Vladimir Dergachev wrote:

On Sat, 9 Oct 2021, Jeff Newmiller wrote:

Keep in mind that by embedding this decision into your package you may be 
consuming a resource (cores) that may be more efficiently allocated by an 
application-level partitioning. of available resources. I for one am not a 
fan of this kind of thinking, and it makes system requirements for your 
package more complex even if you allow me to disable it.

That's right, and this is why I was asking about any present or future 
plans for R support - if there was a way to find out how many threads R 
should use, I would use that.

So far, it looks like the most portable way is to use OpenMP and let the 
user set an appropriate environment variable if they want to restrict 
thread usage. I could use the same OpenMP variable for pthreads as well.

This is pretty common on clusters anyway, with openmp environment variables 
set automatically to the number of cores user requested.

I would probably also add a function to the package to report the number of 
threads being used. Not sure whether it would be a good idea to report this 
during package loading (and not sure what is the right way to display a 
message during package load either).

best

Vladimir Dergachev

-- 
Dr. Benjamin Bolker
Professor, Mathematics & Statistics and Biology, McMaster University
Director, School of Computational Science and Engineering
Graduate chair, Mathematics & Statistics