Controlling threads

[mayer79]

How to control the number of threads used by XGBoost (and most probably its dependency data.table)?

In CRAN submissions, I got

* checking tests ... [41s/4s] NOTE
  Running ‘testthat.R’ [41s/4s]
Running R code in ‘testthat.R’ had CPU time 9.4 times elapsed time

Similar for examples.

Consequence:

• All examples -> dontrun
• All unit tests using XGBoost commented out -> low test coverage

There are discussions on the R dev mailing list that CRAN might limit resources per package from their side. But of course, it would be great to fix the problem already now.

What I have tried:

1. Set params = list(nthread = 1) in all XGBoost tests
2. Set nrounds = 1 in all XGBoost tests
3. Set environment variables in the test script before loading {shapviz}. I think this does not work because the session has already started at that moment.
4. Set `data.table::setDTthreads(1) in the test script.

Any hints?

[jmaspons]

Perhaps setting xgb.DMatrix(..., nthreads = 1)

[mayer79]

Oh, that is indeed possible! I will definitively check during the next submission. I am not sure how to check beforehand: check_rhub(platforms = "debian-gcc-devel") does not seem to detect the problem.