Control the number of threads¶

brille runs its parallel sections on a pool of native threads. Methods that take a threads argument use that many threads when it is one or more. When it is less than one, which is the default, the number comes from the BRILLE_NUM_THREADS environment variable, or is one thread per logical core if that is not set.

BRILLE_NUM_THREADS=4 python my_script.py

Set it when several processes use brille at once, for example parallel fits or pytest-xdist workers, so that together they don't ask for more threads than the machine has cores. The value must be a positive integer; anything else is ignored.

It is read each time the pool is sized, so it can also be changed from Python between calls:

import os
os.environ["BRILLE_NUM_THREADS"] = "2"

OMP_NUM_THREADS has no effect, since brille no longer uses OpenMP.