R package to CRAN: had CPU time 5 times elapsed time

Question

just providing my solution to the issue that occurs when submitting a package to CRAN and getting an error similar to this:

* checking tests ... [838s/167s] NOTE
  Running ‘testthat.R’ [838s/167s]
Running R code in ‘testthat.R’ had CPU time 5 times elapsed time

Now I couldn't replicate this error (locally, on win-hub or rhub) and found very little information on this.

Answer 1

I found a few helpful discussions on the R-pkg-devel mailing list: The result of the R-core discussions here or a question for another package that had the same issue here with the solution on GitHub here.

Essentially the issue is related to the number of CPU cores used by a package - and the CRAN policy to try to avoid a package using too many by default.

The solution involves setting the variable OMP_THREAD_LIMIT to 2. For this, I created a new file called packagename.R that looked like this:

.onLoad <- function(libname, pkgname) {
  # CRAN OMP THREAD LIMIT
  Sys.setenv("OMP_THREAD_LIMIT" = 2)

}

And this did the trick when submitting it to CRAN next time around. Hopefully this is useful to others as well!