online: Use same number of threads as openmp.

added Online label

requested review from @s.zharko

assigned to @fweig

approved this merge request

enabled an automatic merge when the pipeline for d2c8aa8d succeeds

Dear @d.smith, @fweig,

you have been identified as code owner of at least one file which was changed with this merge request.

Please check the changes and approve them or request changes.

added CodeOwners label

merged