concurrent.py

from time import time
from concurrent.futures import ProcessPoolExecutor    

def gcd(pair):
    a, b = pair
    low = min(a, b)
    for i in range(low, 0, -1):
        if a % i == 0 and b % i == 0:
            return i

numbers = [(1963309, 2265973), (2030677, 3814172),
           (1551645, 2229620), (2039045, 2020802)]
if __name__ == "__main__":
    start = time()
    results = list(map(gcd, numbers))
    end = time()
    print('Took %.3f seconds' % (end - start))

    start = time()
    pool = ProcessPoolExecutor(max_workers = 2)  # The one change
    results = list(pool.map(gcd, numbers))
    end = time()
    print('Took %.3f seconds' % (end - start))