python併發任務(六) 多線程

解決CPU密集型：如判斷10000個數是否是素數

下面的程序比較單線程  多線程 以及多進程在計算素數的時間差異

結論： 對於CPU密集型的計算，多線程會可能比單線程更耗時，多進程則時間更短

from logging import StreamHandler
import math
import time

from flask.app import Flask
from concurrent.futures import ThreadPoolExecutor, ProcessPoolExecutor


PRIMES = [112272535095293] * 20

def is_prime(n):
    if n < 2:
        return False
    if n == 2:
        return True
    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 single_thread():
    for number in PRIMES:
        is_prime(number)


def multi_thread():
    with ThreadPoolExecutor() as pool:
        pool.map(is_prime, PRIMES)


def multi_process():
    with ProcessPoolExecutor() as pool:
        pool.map(is_prime, PRIMES)


if __name__ == '__main__':
    start = time.time()
    single_thread()
    end = time.time()
    print('single_thread, cost: ', end-start, "seconds")

    start = time.time()
    multi_thread()
    end = time.time()
    print('multi_thread, cost: ', end-start, "seconds")

    start = time.time()
    multi_process()
    end = time.time()
    print('multi_process, cost: ', end-start, "seconds")