Vector clock algorithm for DS Lab8

main.py

"""
  This is the improved version of the code given in the article
  https://towardsdatascience.com/understanding-lamport-timestamps-with-pythons-multiprocessing-library-12a6427881c6

  Shows three communicating processes with the vector clock for synchronization.
  
  Result of running this code is:
  Final vector in A is [7, 8, 3]
  Final vector in B is [4, 8, 3]
  Final vector in C is [1, 5, 4]
"""

from multiprocessing import Process, Pipe
from os import getpid
from datetime import datetime
from time import sleep

def final_count(pid, counter):
    name = ''
    if (pid == 0):
       name = 'A'
    elif (pid == 1):
       name = 'B'
    elif (pid == 2):
       name = 'C'
    print('Final vector in {} is {}'.format(name, counter))

# Calculate the weights of the vector during the requests
def calc_recv_timestamp(recv_time_stamp, counter):
    for id  in range(len(counter)):
        counter[id] = max(recv_time_stamp[id], counter[id])
    return counter

# Custom event inside the process
def event(pid, counter):
    counter[pid] += 1
    return counter

# Send some text to the neighbor process
def send_message(pipe, pid, counter):
    counter[pid] += 1
    pipe.send(('Empty shell', counter))
    return counter

# Wait for the message from another process with request
def recv_message(pipe, pid, counter):
    message, timestamp = pipe.recv()
    counter = calc_recv_timestamp(timestamp, counter)
    counter[pid] += 1
    return counter

# Define processes with their events
def process_a(pipeab):
    pid = 0
    counter = [0,0,0]
    counter = send_message(pipeab, pid, counter)
    counter  = event(pid, counter)
    counter  = event(pid, counter)
    counter = send_message(pipeab, pid, counter)
    counter  = event(pid, counter)
    counter = recv_message(pipeab, pid, counter)
    counter = recv_message(pipeab, pid, counter)
    final_count(pid, counter)

def process_b(pipebc, pipeba):
    pid = 1
    counter = [0,0,0]
    counter = recv_message(pipebc, pid, counter)
    counter = recv_message(pipebc, pid, counter)
    counter = recv_message(pipeba, pid, counter)
    counter  = event(pid, counter)
    counter = send_message(pipebc, pid, counter)
    counter = recv_message(pipeba, pid, counter)
    counter = send_message(pipeba, pid, counter)
    counter = send_message(pipeba, pid, counter)
    final_count(pid, counter)

def process_c(pipecb):
    pid = 2
    counter = [0,0,0]
    counter = send_message(pipecb, pid, counter)
    counter  = event(pid, counter)
    counter = send_message(pipecb, pid, counter)
    counter = recv_message(pipecb, pid, counter)
    final_count(pid, counter)

# Create processes, initialize pipes and make them run
if __name__ == '__main__':
    oneandtwo, twoandone = Pipe()
    twoandthree, threeandtwo = Pipe()

    process1 = Process(target=process_c, 
                       args=(oneandtwo,))
    process2 = Process(target=process_b, 
                       args=(twoandone, twoandthree))
    process3 = Process(target=process_a, 
                       args=(threeandtwo,))

    process1.start()
    process2.start()
    process3.start()

    process1.join()
    process2.join()
    process3.join()