我正在尝试学习使用Python的Multiprocessing模块。作为第一个测试,我想我将同时运行四个15秒的过程。我写了这个模块,叫做“ multiPtest.py”:
import time
import timeit
import multiprocessing
def sleepyMe(napTime):
time.sleep(napTime)
print "Slept %d secs" % napTime
def tester(numTests):
#Launch 'numTests' processes using multiProcessing module
for _ in range(numTests):
p = multiprocessing.Process(target=sleepyMe(15))
p.start() #Launch an 'independent' process
#p.join() ##Results identical with or without join
def multiTester():
#Time running of 4 processes
totTime = timeit.Timer('tester(4)', setup = 'from multiPtest import tester').repeat(1,1)
print "Total = ", totTime[0]
但是,当我跑步时,会得到以下结果:
Python 2.7.6 (default, Mar 22 2014, 22:59:56)
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from multiPtest import *
>>> multiTester()
Slept 15 secs
Slept 15 secs
Slept 15 secs
Slept 15 secs
Total = 60.0739970207
我本来希望总时间接近15秒,而不是60秒。我知道我有4个内核,因为我查看了/ proc / cpuinfo:
~/Projects/PythonProjects$ cat /proc/cpuinfo
processor : 0
vendor_id : GenuineIntel
cpu family : 6
model : 60
model name : Intel(R) Core(TM) i7-4900MQ CPU @ 2.80GHz
stepping : 3
microcode : 0x17
cpu MHz : 800.000
cache size : 8192 KB
physical id : 0
siblings : 8
core id : 0
cpu cores : 4
...
为什么我看不到这四个卧铺同时入睡?在其他人处于睡眠/忙碌状态时,我是否应该能够创建和启动新流程?我是否误解了有关多处理,Python的多处理模块或其他方面的东西?
python大神给出的解决方案
在行中
p = multiprocessing.Process(target=sleepyMe(15))
您实际上已经调用了sleepyMe
,并将结果(None
)用作target
参数的值,因此需要等待15秒钟。尝试
p = multiprocessing.Process(target=sleepyMe, args=(15, ))
并将函数修改为for循环后的所有子进程join()
,否则它将立即返回,并且最终总时间接近于零。