from concurrent import futures
import multiprocessing
import math
import sys, time
import functools

MIN = 100000000
MAX = 100100000

def is_prime(n):
    if n % 2 == 0:
        return False

    sqrt_n = int(math.floor(math.sqrt(n)))
    for i in range(3, sqrt_n + 1, 2):
        if n % i == 0:
            return False
    return True


def fn2(fn, chunk):
    return [fn(*args) for args in zip(*chunk)]

class FastProcessPoolExecutor(futures.ProcessPoolExecutor):
    def map(self, fn, *iterables, timeout=None, chunksize=None):
        try:
            iter_len = min(len(i) for i in iterables)
        except TypeError:
            # At least one iterable has no length
            return super().map(fn, *iterables, timeout)

        fn3 = functools.partial(fn2, fn)

        if chunksize is None:
            chunksize, extra = divmod(iter_len, self._max_workers * 4)
            if extra:
                chunksize += 1

        if timeout is not None:
            end_time = timeout + time.time()

        fs = [self.submit(fn3, [iterable[ch:ch+chunksize]
                                for iterable in iterables])
              for ch in range(0, iter_len, chunksize)]

        try:
            for future in fs:
                if timeout is None:
                    for i in future.result():
                        yield i
                else:
                    for i in future.result(end_time - time.time()):
                        yield i
        finally:
            for future in fs:
                future.cancel()


print("Starting multiproc...", end="")
start = time.time()
p = multiprocessing.Pool(4)
l = p.map(is_prime, range(MIN, MAX))
stop = time.time()
print("done in {} s.".format(stop - start))

print("Starting futures...", end="")
start = time.time()
e = futures.ProcessPoolExecutor(4)
f = e.map(is_prime, range(MIN, MAX))
l2 = list(f)
stop = time.time()
print("done in {} s.".format(stop - start))

print('Starting futures "fixed"...', end="")
start = time.time()
e = FastProcessPoolExecutor(4)
f = e.map(is_prime, range(MIN, MAX))
l3 = list(f)
stop = time.time()
print("done in {} s.".format(stop - start))

print("l == l2:", l == l2)
print("l == l3:", l == l3)