multiprocess :: mp.cpu_count() instead of len(os.sched_getaffinity(0))

[EricDeveaud]

Hello

sumtree.py get number of cpus using num_cpus = multiprocessing.cpu_count() which may be innacurate in a taskset context or a slurm allocation for example.

see:

$ nproc
96
$ taskset -c 1 nproc
1
$ taskset -c 1 python3 -c "import multiprocessing; print(multiprocessing.cpu_count())"
96

I would suggest to use len(os.sched_getaffinity(0)) instead of multiprocessing.cpu_count()

$ python3 -c "import os; print(len(os.sched_getaffinity(0)))"
96
$ taskset -c 1 python3 -c "import os; print(len(os.sched_getaffinity(0)))"
1

regards

Eric