This post provides an implementation of SimPy’s Movie Renege example. In this implementation I subclassed three times. One class is TicketArrivalNode which replaces the ordinary ciw.ArrivalNode in order for individuals to be given tickets when they arrive in the simulation. The TheatreNode class keeps track of which movies there are and whether they are sold out. Lastly RenegeAtServiceDist is responsible for keeping track of the change in number of tickets and assigning whether a customer reneged.
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import random
from typing import NoReturn
import ciw
import matplotlib.pyplot as plt
import pandas as pd
import seaborn as sns
movies = ['Python Unchained', 'Kill Process', 'Pulp Implementation']
class TicketArrivalNode(ciw.ArrivalNode):
"""Node generating customers requiring tickets.
Attributes:
None
Methods:
send_individual: Assigns individuals a random number of tickets and a movie choice.
"""
def send_individual(self, next_node: ciw.Node, next_individual: ciw.Individual) -> NoReturn:
"""Assigns individuals to have a required number of tickets for a movie.
Args:
next_node: The next node in the simulation.
next_individual: The individual to assign tickets to.
Returns:
None
"""
next_individual.num_tickets = random.randint(1,6)
next_individual.movie = random.choice(movies)
next_node.accept(next_individual)
class TheatreNode(ciw.Node):
"""Node representing the theatre in the simulation.
Attributes:
num_renegers (dict): Dictionary to track the number of reneging customers.
available_movies (dict): Dictionary to track available tickets for each movie.
sold_out (dict): Dictionary to track whether each movie is sold out.
sold_out_time (dict): Dictionary to track the time each movie sold out.
Methods:
__init__: Initializes the TheatreNode object.
write_individual_record: Writes a data record for an individual when leaving the node.
"""
def __init__(self, *args, **kwargs) -> NoReturn:
"""Initializes the TheatreNode object."""
super().__init__(*args, **kwargs)
self.num_renegers = {}
self.available_movies = {movie:50 for movie in movies}
self.sold_out = {movie:False for movie in movies}
self.sold_out_time = {movie:float('inf') for movie in movies}
def write_individual_record(self, individual: ciw.Individual):
"""Write a data record for an individual when leaving a node.
Args:
individual: The individual leaving the node.
Returns:
None
"""
if ciw.node.isinf(self.c) or self.slotted:
server_id = False
else:
server_id = individual.server.id_number
record = ciw.DataRecord(
id_number=individual.id_number,
customer_class=individual.previous_class,
original_customer_class=individual.original_class,
node=self.id_number,
arrival_date=individual.arrival_date,
waiting_time=individual.service_start_date - individual.arrival_date,
service_start_date=individual.service_start_date,
service_time=individual.service_end_date - individual.service_start_date,
service_end_date=individual.service_end_date,
time_blocked=individual.exit_date - individual.service_end_date,
exit_date=individual.exit_date,
destination=individual.destination,
queue_size_at_arrival=individual.queue_size_at_arrival,
queue_size_at_departure=individual.queue_size_at_departure,
server_id=server_id,
record_type="renege" if individual.reneged_at_service else "service",
)
individual.data_records.append(record)
class RenegeAtServiceDist(ciw.dists.Distribution):
"""Distribution to handle reneging at service time.
Attributes:
dist_accept: Distribution for accepting customers.
dist_renege: Distribution for reneging customers.
Methods:
__init__: Initializes the RenegeAtServiceDist object.
sample: Samples the distribution to determine if a customer will renege.
"""
def __init__(self, dist_accept: ciw.dists.Distribution, dist_renege: ciw.dists.Distribution) -> float:
"""Initializes the RenegeAtServiceDist object."""
self.dist_accept = dist_accept
self.dist_renege = dist_renege
def sample(self, t=None, ind=None):
"""Samples the distribution to determine if a customer will renege.
Args:
t: Time parameter for the distribution (default is None).
ind: Individual to sample for (default is None).
Returns:
float: The sampled value from the distribution.
"""
selected_individual = ind
selected_movie = selected_individual.movie
current_node = selected_individual.simulation.nodes[selected_individual.node]
available_tickets = current_node.available_movies[selected_movie]
movie_sold_out = current_node.sold_out[selected_movie]
insufficient_tickets = available_tickets < selected_individual.num_tickets
if movie_sold_out or insufficient_tickets:
selected_individual.reneged_at_service = True
else:
selected_individual.reneged_at_service = False
current_node.available_movies[selected_movie] -= selected_individual.num_tickets
if current_node.available_movies[selected_movie] < 2:
current_node.sold_out[selected_movie] = True
available_tickets = 0
current_node.sold_out_time[selected_movie] = selected_individual.simulation.current_time
if ind.reneged_at_service:
return self.dist_renege.sample()
return self.dist_accept.sample()
network = ciw.create_network(
arrival_distributions=[ciw.dists.Exponential(2)],
service_distributions=[
RenegeAtServiceDist(
ciw.dists.Deterministic(1.0),
ciw.dists.Deterministic(0.5)
)
],
number_of_servers=[1]
)
results = []
for i in range(10):
simulation = ciw.Simulation(network, arrival_node_class=TicketArrivalNode, node_class=TheatreNode)
simulation.simulate_until_max_time(120)
results.append(simulation.nodes[1].sold_out_time)
results = pd.DataFrame(results, columns=results[0].keys())
sns.boxplot(data=results)
plt.savefig('ciw_simpy_movie_renege.png', dpi=300)
plt.close()