多进程信息的输出

Question

我正在尝试学习更多关于使用Python进行多处理的知识。我正在使用multiprocessing模块，但我无法理解它是如何工作的。这些是为实现多进程而编写的函数

import multiprocessing as mp
import os
import random

zones = []

for i in range(0,10):
    x = random.randint(1,10)
    zones.append(x)
def chunks(l, n):
    for i in range(0, len(l), n):
        yield l[i:i + n]
def info(title):
    print(title)
    print( 'module name:', __name__)
    if hasattr(os, 'getppid'):  # only available on Unix
        print('parent process:', os.getppid())
    print( 'process id:', os.getpid())

def worker(x):

    for i in range(0,5):
        print( x * i)

def main():


    man = mp.Manager()
    split = chunks(zones, len(zones)//4)
    for z in split:
        info('==========')
        p = mp.Process(target=worker,args=(z,))
        print(p)
        p.start()
if __name__ == '__main__':
    mp.set_start_method('fork')
    main()

我在shell上得到了这个输出

    ==========
module name: __main__
parent process: 5226
process id: 7774
<Process(Process-2, initial)>
==========
module name: __main__
parent process: 5226
process id: 7774
<Process(Process-3, initial)>
[]
[1, 1]
[1, 1, 1, 1]
[1, 1, 1, 1, 1, 1]
[1, 1, 1, 1, 1, 1, 1, 1]
==========
module name: __main__
parent process: 5226
process id: 7774
<Process(Process-4, initial)>
[]
[5, 2]
[5, 2, 5, 2]
[5, 2, 5, 2, 5, 2]
[5, 2, 5, 2, 5, 2, 5, 2]
==========
module name: __main__
parent process: 5226
process id: 7774
<Process(Process-5, initial)>
==========
module name: __main__
parent process: 5226
process id: 7774
[]
<Process(Process-6, initial)>
[5, 3]
[5, 3, 5, 3]
[5, 3, 5, 3, 5, 3]
[5, 3, 5, 3, 5, 3, 5, 3]
[]
[9, 10]
[9, 10, 9, 10]
[9, 10, 9, 10, 9, 10]
[9, 10, 9, 10, 9, 10, 9, 10]
[]
[1, 7]
[1, 7, 1, 7]
[1, 7, 1, 7, 1, 7]
[1, 7, 1, 7, 1, 7, 1, 7]

为什么这个过程总是相同的，而且不会改变？因为我将进程分成几个部分，所以我希望代码在不同的进程id上运行。

Answer 1

你的员工都不会给info打电话。试试这个：

import multiprocessing as mp
import os

def info():
    print("==")
    print('module name:', __name__)
    print('parent process:', os.getppid())
    print('process id:', os.getpid())

def worker(arg):
    info()
    print("worker arg: {}".format(arg, ))

man = mp.Manager()
for z in [1,2,3,4]:
    p = mp.Process(target=worker,args=(z,))
    p.start()

输出：

==
module name: __main__
parent process: 2253
process id: 2256
worker arg: 1
==
module name: __main__
parent process: 2253
process id: 2258
worker arg: 3
==
module name: __main__
parent process: 2253
process id: 2257
worker arg: 2
==
module name: __main__
parent process: 2253
process id: 2259
worker arg: 4

Answer 2

您将从主进程而不是子进程的循环中调用函数info。

根据以下内容调整代码：

from multiprocessing import Process
import os

def info(title):
  print(title)
  print('module name:', __name__)
  print('parent process:', os.getppid())
  print('process id:', os.getpid())

## Function chunks used to divide the input files into slices
zones=[1,2,3,4]
for z in zones:
  p = Process(target=info,args=(z,))
  p.start()
  p.join()

输出：

 python multiprocess.py
1
('module name:', '__main__')
('parent process:', 47974)
('process id:', 47975)
2
('module name:', '__main__')
('parent process:', 47974)
('process id:', 47976)
3
('module name:', '__main__')
('parent process:', 47974)
('process id:', 47977)
4
('module name:', '__main__')
('parent process:', 47974)
('process id:', 47978)