How to limit the number of OpenBLAS threads on RStudio Server

We are running Ubuntu 20.04 with RStudio Server Open Source. The system is using OpenBLAS for linear algebra.

What are the different ways to limit the number of threads on a per user base used for linear algebra from within RStudio Server?

I have tried setting

export OPENBLAS_NUM_THREADS=4

in .profile and .bashrc but neither works.

I haven't tried [1] yet. Are there other ways? I would like to make a low number of threads the default for everyone because users are not aware of the different types of parallelism and oversubscribe cores.

I am also not able to limit the number of threads for all users, I have tried setting them in

/etc/environment
/etc/rstudio/env-vars

and also with

systemctl edit rstudio-server.service

nothing works.

[1] https://github.com/wrathematics/openblasctl

There is also package for this allowing you to set the usual OpenBLAS / MKL variables from R: https://cran.r-project.org/package=RhpcBLASctl

It also allows you to query for cores and processors and allocated for both BLAS and OpenMP:

> library(RhpcBLASctl)
> get_num_cores()
[1] 6
> get_num_procs()        # hyperthreading on
[1] 12
> blas_set_num_threads(4)
> 
> 

If you want to set this more permanently, the usual place is Renviron.site for the underlying environment variable, or Rprofile.site if you want to do it from R code via Sys.setenv() -- or to call this helper package. How the startup variable setting sequence works in explained in help(Startup).