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Assignment 2 Online shopping routine

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Computer Operating Systems
Assignment 2
I. Introduction
The subject of this assignment is to design an online shopping routine using multiprocessing
and multithreading concepts in operating systems (OS). In an online shopping routine, more
than one customer can order at the same time and this can cause a problem called race
condition. When more than one customer wants to purchase the same product at the same
time, this flow should be managed with a proper synchronization mechanism avoiding any
race condition. Otherwise, the program may have some unexpected/inconsistent outputs. For
instance, two customers may order product1 which is n in stock initially. They may reach and
modify the same product (shared resource) concurrently and both processes/threads read
the stock as n, and the count of the product may be decreased just one time instead of two
times. To prevent race condition in OS, mutual exclusion methods are used. In this
assignment, you are asked to perform a properly working online shopping routine using
mutexes.
Sample structures for customer and product are given as follows:
struct Customer
customer_ID Unique value for identifying each customer (Start from 1 and increment by one)
customer_Balance Customer’s available money in their account (between 0 – 200$).
ordered_Items The list of products to be purchased.
purchased_Items The list of all items purchased in an order (*with the quantity of each product).
*Add more members if needed.
struct Product
product_ID Unique value for identifying each product.
product_Price Price of the product (between 1 – 200$).
product_Quantity Quantity of the products in stock (1-10 for each).
*Add more members if needed.
NOTE: You can randomly generate the balance, price and quantity values according to
given ranges above.
II. Implementation Rules
● A purchase request (ordered_Items) is sent by specifying the products to be purchased
and their quantities.
● If the desired product quantity is in stock, it can be purchased if the budget (balance) is
sufficient.
● A customer can order at most five items (quantity) of the same product.
● More than one customer can order at the same time for the same product.
● A customer’s balance can never be less than 0. In other words, if the price of the
product to be purchased is more than the balance, the purchase will not be accepted.
● A customer can order a single product (Scenario 1) or list of products (Scenario 2) at
the same time.
o Ordering single product at a time: order_product(product_id,quantity)
o Ordering a list of products at a time: order_products (find out a proper way to
pass arguments)
o Be careful that in Scenario 2, the customer may buy all/several or none of the
products ordered. For example, if customer1 orders 5 of product1 and 3 of
product2 whose stocks are 4 and 3, respectively, customer1 can buy only 3 of
product2.
● Once the purchases are finalized, the total balance, purchased products list, and
inventory are updated (i.e. the purchase price is deducted from the total balance, the
purchased quantity is deducted from the stock for each product).
● There must be at least 3 customers and 5 products created in your codes.
III. Output
At the end of the shopping process,
● Print out the initial balance, updated balance, ordered_Items and
purchased_Items for each customer.
● Print out the initial products information (id, quantity, price) and updated
products information (id, quantity, price) after each purchase.
Sample output:
Note that the following examples are for the customers who order just one product of the
given quantity at a time. (e.g. Customer1(3,4) means that customer1 ordered 4 of
product3).
Customer 1:
Initial products:
Product ID Quantity Price
1 9 99.36
2 5 78.77
3 5 42.93
4 3 14.40
5 1 18.91
Bought 4 of product 3 for $171.72
Updated products:
Product ID Quantity Price
1 9 99.36
2 5 78.77
3 1 42.93
4 3 14.40
5 1 18.91
Customer1(3,4) success! Paid $42.93 for each.
Customer2(3,2) fail! Only 1 left in stock.
Customer1(4,1) fail! Insufficient funds.
Customer1———-
initial balance: $180
updated balance: $8.28
Ordered products:
id quantity
3 4
4 1
Purchased products:
id quantity
3 4

Customer2———-
initial balance: $150
updated balance: $150
Ordered products:
id quantity
3 2
Purchased products:
id quantity
– –
IV. Implementation Details
In this assignment, you can create multiple processes and threads that represent
customers (e.g. customer1, customer2, customer3, …). You may create a customer
class and produce multiple processes/threads as instances. The customer_ID is a
unique integer that starts from 1 and increases by one. The customer_Balance a is
double which is assigned in the range of [1, 200]. You need to create at least 3
customer instances for each method.
The products will be created at the beginning of the program so customers can buy any
of them. Again, you can follow the class-instances pattern for product creation. The
product_id is a unique integer that starts from 1 and increases by one. The
product_Price is a double which will be randomly assigned in the range of [1,200]. The
product_Quantity is an integer which is also randomly assigned between 1 to 10. You
need to create at least 5 product instances.
V. Submission Rules
You should upload a zip archive file containing the following items:
i. Your report that explains your code and contains a discussion section where
you will answer the following questions:
○ Which one of the two methods works faster? Explain. (You can prove
your answer by adding a code snippet which calculates the execution
time of each program)
○ Assuming there are simultaneously 10000 active customers in the
shopping system you implemented, which methodology (multiprocessing
vs multithreading) is more efficient to use? Why?
ii. Source files containing your C programs.
iii. makefile for each program (multiprocessing vs multithreading).
● Under the zip folder you can separate multithreading and multiprocessing as two
main folders.
● Prepare your report in LaTeX format to get full marks. You can use the following
template: https://www.overleaf.com/read/dqshxtrpthgh
● Your report must not exceed 5 pages.
● Any form of plagiarism will not be tolerated. You must code by yourself in a neat
way and explain the details, so that there are no unclear parts left in your code.
● You must implement your solution in the C programming language and make sure
that it works on a linux environment.
For any queries, please contact T.A. ayvaz18@itu.edu.tr

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