我发现了一些与Python多进程相关的行为,但我很难理解。
使用Pool时,即使只有一个进程,它的性能也会更快。
为什么会这样呢?是因为多进程可以对代码进行优化吗?
import time
from multiprocessing import Pool
fib_input = [24] * 10
def fib(n):
if n in [0,1]:
return 1
return fib(n-1)+fib(n-2)
def main1():
with Pool(processes=1) as p:
results = p.map(fib, fib_input)
print (results)
def main2():
results = list(map(fib, fib_input))
print (results)
if __name__ == "__main__":
start_time = time.time()
main1()
print("--- %s seconds ---" % (time.time() - start_time))
start_time = time.time()
main2()
print("--- %s seconds ---" % (time.time() - start_time))
输出:
[75025, 75025, 75025, 75025, 75025, 75025, 75025, 75025, 75025, 75025]
--- 0.47702741622924805 seconds ---
[75025, 75025, 75025, 75025, 75025, 75025, 75025, 75025, 75025, 75025]
--- 7.922452926635742 seconds ---
main2()
更快:[75025, 75025, 75025, 75025, 75025, 75025, 75025, 75025, 75025, 75025] --- 0.426348924637 秒 --- [75025, 75025, 75025, 75025, 75025, 75025, 75025, 75025, 75025, 75025] --- 0.31747508049 秒 ---
- Amit Kumar Gupta0.23288583755493164秒
对比0.1788322925567627秒
。 - Daniil Ryzhkov