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from __future__ import annotations
import math
from dask.system import CPU_COUNT
def _factors(n: int) -> set[int]:
"""Return the factors of an integer
https://stackoverflow.com/a/6800214/616616
"""
seq = ([i, n // i] for i in range(1, int(pow(n, 0.5) + 1)) if n % i == 0)
return {j for item in seq for j in item}
def nprocesses_nthreads(n=CPU_COUNT):
"""
The default breakdown of processes and threads for a given number of cores
Parameters
----------
n : int
Number of available cores
Examples
--------
>>> nprocesses_nthreads(4)
(4, 1)
>>> nprocesses_nthreads(32)
(8, 4)
Returns
-------
nprocesses, nthreads
"""
if n <= 4:
processes = n
else:
processes = min(f for f in _factors(n) if f >= math.sqrt(n))
threads = n // processes
return (processes, threads)
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