import sys
import time
import hashlib
from concurrent import futures
from random import randrange

JOBS = 12
SIZE = 2**20
STATUS = '{} workers, elapsed time: {:.2f}s'


def sha(size):
    data = bytearray(randrange(256) for i in range(size))
    algo = hashlib.new('sha256')
    algo.update(data)
    return algo.hexdigest()


def main(workers=None):
    if workers:
        workers = int(workers)
    t0 = time.time()

    with futures.ProcessPoolExecutor(workers) as executor:
        actual_workers = executor._max_workers
        to_do = (executor.submit(sha, SIZE) for i in range(JOBS))
        for future in futures.as_completed(to_do):
            res = future.result()
            print(res)

    print(STATUS.format(actual_workers, time.time() - t0))

if __name__ == '__main__':
    if len(sys.argv) == 2:
        workers = int(sys.argv[1])
    else:
        workers = None
    main(workers)