gistfile1.txt

These are my results:
{1: 2.327260809430917,
 2: 1.7694565749482591,
 3: 1.3241503620006503,
 4: 0.7659831585049286,
 5: 0.786389897507167,
 6: 0.4727930181724931,
 7: 0.5592591157981355,
 8: 0.5410198394120904,
 9: 0.4966728396999276,
 'sync': 0.002815263798666064}

Why is synchronous so much faster?


####
from time import clock as time

from concurrent.futures import ProcessPoolExecutor


def factorize_naive(n):
    """ A naive factorization method. Take integer 'n', return list of
        factors.
    """
    if n < 2:
        return []
    factors = []
    p = 2

    while True:
        if n == 1:
            return factors

        r = n % p
        if r == 0:
            factors.append(p)
            n = n // p
        elif p * p >= n:
            factors.append(n)
            return factors
        elif p > 2:
            # Advance in steps of 2 over odd numbers
            p += 2
        else:
            # If p == 2, get to 3
            p += 1
    assert False, "unreachable"


if __name__ == '__main__':
    nums = range(1000)

    result = {}

    t = time()
    map(factorize_naive, nums)
    result['sync'] = time() - t

    for i in xrange(1, 10):
        print i
        t = time()
        with ProcessPoolExecutor(max_workers=i) as executor:
            list(executor.map(factorize_naive, nums))
        result[i] = time() - t

    from pprint import pprint
    pprint(result)