Modeling a Car Wash

Faisal Qureshi
faisal.qureshi@ontariotechu.ca
http://www.vclab.ca

Copyright information

© Faisal Qureshi

License

This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.

Setup

A carwash shop has a limited number of washing stations. Each car takes "some time" to be washed. The time that each car takes is bounded by some range, e.g., it may take a car to be washed any where between 3 and 7 minutes. Each washing station can only clean a single are at each time. Cars arrive at the carwash shop, wait for a wash station to become available, and gets washed.

Acknowledgements

This code is adapted from simpy examples.

import random
import simpy

class Carwash(object):
    
    def __init__(self, env, num_wash_stations, washtimes):
        self.env = env
        self.wash_stations = simpy.Resource(env, num_wash_stations)
        self.washtimes = washtimes

    def wash(self, car):

12 13 9 8 13 12 14 11 11 14 12 7 8 9 11 12 7 14 12 9 8 10 11 14 11 13 12 12 14 13 11 8 12 12 11 14 12 11 11 10 12 8 13 11 11 8 11 13 10 11 10 9 11 9 11 12 12 14 12 7 14 10 7 12 13 12 11 10 14 12 12 9 9 8 11 11 7 7 8 10 9 11 10 8 13 11 12 9 10 9 10 7 10 13 12 13 13 11 10 9
        
        a, b = washtimes
        washtime =  random.randint(a, b)
        print(washtime)
        yield self.env.timeout(washtime)

def car(env, name, cw):
    print(f'{name} arrives at the carwash shop at {env.now}')
    
    with cw.wash_stations.request() as request:
        yield request
        print(f'{name} enters the carwash at {env.now}')
        yield env.process(cw.wash(name))
        print(f'{name} leaves the carwash at {env.now}')

def setup(env, 
          num_wash_stations, 
          wash_times, 
          time_between_arrivals):
    carwash_shop = Carwash(env, num_wash_stations, time_between_arrivals)
    i = 0
    while True:
        a, b = time_between_arrivals
        arrival_time = random.randint(a, b)       
        yield env.timeout( arrival_time )
        i += 1
        env.process( car(env, 'car %d' % i, carwash_shop) )

print('Carwash Simulation')

seed = 42
random.seed(seed) 

num_wash_stations = 4
washtimes = (10,16)
time_between_arrivals = (2,3)
simulation_duration = 60

env = simpy.Environment()
env.process( setup(env, num_wash_stations, washtimes, time_between_arrivals) )
env.run(until=simulation_duration)

Carwash Simulation
car 1 arrives at the carwash shop at 2
car 1 enters the carwash at 2
15
car 2 arrives at the carwash shop at 4
car 2 enters the carwash at 4
11
car 3 arrives at the carwash shop at 7
car 3 enters the carwash at 7
11
car 4 arrives at the carwash shop at 9
car 4 enters the carwash at 9
15
car 5 arrives at the carwash shop at 11
car 6 arrives at the carwash shop at 13
car 2 leaves the carwash at 15
car 5 enters the carwash at 15
10
car 7 arrives at the carwash shop at 16
car 1 leaves the carwash at 17
car 6 enters the carwash at 17
10
car 8 arrives at the carwash shop at 18
car 3 leaves the carwash at 18
car 7 enters the carwash at 18
11
car 9 arrives at the carwash shop at 20
car 10 arrives at the carwash shop at 22
car 11 arrives at the carwash shop at 24
car 4 leaves the carwash at 24
car 8 enters the carwash at 24
11
car 5 leaves the carwash at 25
car 9 enters the carwash at 25
13
car 12 arrives at the carwash shop at 27
car 6 leaves the carwash at 27
car 10 enters the carwash at 27
16
car 7 leaves the carwash at 29
car 11 enters the carwash at 29
16
car 13 arrives at the carwash shop at 30
car 14 arrives at the carwash shop at 32
car 15 arrives at the carwash shop at 34
car 8 leaves the carwash at 35
car 12 enters the carwash at 35
12
car 16 arrives at the carwash shop at 37
car 9 leaves the carwash at 38
car 13 enters the carwash at 38
11
car 17 arrives at the carwash shop at 40
car 18 arrives at the carwash shop at 42
car 10 leaves the carwash at 43
car 14 enters the carwash at 43
10
car 19 arrives at the carwash shop at 45
car 11 leaves the carwash at 45
car 15 enters the carwash at 45
13
car 20 arrives at the carwash shop at 47
car 12 leaves the carwash at 47
car 16 enters the carwash at 47
12
car 21 arrives at the carwash shop at 49
car 13 leaves the carwash at 49
car 17 enters the carwash at 49
14
car 22 arrives at the carwash shop at 52
car 14 leaves the carwash at 53
car 18 enters the carwash at 53
16
car 23 arrives at the carwash shop at 55
car 24 arrives at the carwash shop at 57
car 15 leaves the carwash at 58
car 19 enters the carwash at 58
14
car 16 leaves the carwash at 59
car 20 enters the carwash at 59
10