from multiprocessing import Pool

def f():

    return sum(range(50000))

if __name__ == '__main__':

    pool = Pool(processes=-3)
    #pool = Pool(processes=0)
    #pool = Pool(processes=3)

    results = []
    for i in range(3):

        result = pool.apply_async(f)
        results.append(result)

    pool.close()
    pool.join()

    for result in results:
        print result.get()