Question

Use vi to make a python program that defines three functions waiting for two, three, and four seconds respectively and creates a process for each function, then starts the processes one by one.

Output the number of CPU/ processes once all processes have been started, then for each child process, output its name and id. Then indicate the end of the program.

Each function first outputs the function name, then waits for certain amount of time as specified previously, and indicates the end of the function.

Answer 1

Here's the Python 2.7 code, both the screenshot and the text version including the screenshot of the output.

Text version :

import multiprocessing
import os
import time
def one():
    print("name - one ")
    print("one's pid",os.getpid())
    time.sleep(2)
    print("one completed")

def two():
    print("name - two ")
    print("two's pid",os.getpid())
    time.sleep(3)
    print("two completed")

def three():
    print("name - three ")
    print("three's pid",os.getpid())
    time.sleep(4)
    print("three completed")

if __name__== "__main__":
    # creating separate processes
    p1 = multiprocessing.Process(target=one,)
    p2 = multiprocessing.Process(target=two,)
    p3 = multiprocessing.Process(target=three,)

    # Print Main's Process id
    print("main's pid",os.getpid())
    # Starting Each Process one by one
    p1.start()
    p2.start()
    p3.start()
    p1.join()
    p2.join()
    p3.join()
    print("done") # print once all process has finsihed executing

For the total number of processes running, One parent is calling three children, so the total number of processes running is 4. The generalized method to calculate the total number of process is the number of child processes + 1(for the parent).

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