MacBook Pro ARM only 5 threads are used

[jianshu93]

Hello data.table team,

I have only 5 threads used after successfully installing and library on my MacBook Pro M1 Pro. Any idea why:

data.table 1.14.2 using 5 threads (see ?getDTthreads). Latest news: r-datatable.com

Thank,

Jianshu

[MichaelChirico]

See the NEWS for 1.12.2:

The number of logical CPUs used by default has been reduced from 100% to 50%. The previous 100% default was reported to cause significant slow downs when other non-trivial processes were also running, #3395 #3298. Two new optional environment variables (R_DATATABLE_NUM_PROCS_PERCENT & R_DATATABLE_NUM_THREADS) control this default. setDTthreads() gains percent= and ?setDTthreads has been significantly revised. The output of getDTthreads(verbose=TRUE) has been expanded. The environment variable OMP_THREAD_LIMIT is now respected (#3300) in addition to OMP_NUM_THREADS as before.

AIUI, generally hoovering up all of the available CPUs without user input is a bad practice.

Probably we should write this up into ?"openmp-utils" since it's not there already...