[Rd] Another issue using multi-processing linear algebra libraries

[Ivan Krylov]

В Tue, 6 Aug 2024 10:19:25 -0400
Rob Steele via R-devel <r-devel using r-project.org> пишет:

> Would it make sense to add a parameter somewhere, to mclapply(), say,
> telling R to not use multiprocessing libraries?

It would be great if we had a way to limit all kinds of multiprocessing
(child processes, OpenMP threads, pthreads, forks, MPI, PVM, 'parallel'
clusters, <insert many more methods here>) in a single setting, but
there is currently no such setting, and it may be impossible to
implement. Particularly problematic may be nested parallellism:
sometimes desirable (e.g. 4-machine cluster, each machine in it using
OpenMP threads), sometimes undesired (e.g. your case). A single setting
is probably far from enough.

> Does R even know whether a linked library is doing multi-processing?

Unfortunately, no, there is no standard interface for that. Best I can
recommend is to link your R installation with FlexiBLAS and then use the
'flexiblas' CRAN package to talk to it.

> Does R build its own BLAS and LAPACK if its also linking external
> ones?

I think it doesn't.

-- 
Best regards,
Ivan