COMP3520 Assignment 1 2020
1
COMP3520 Operating Systems Internals
Assignment 1 – Synchronization
General Instructions
This assignment is about synchronization. It consists of two compulsory tasks:
1. write a multithreaded program to solve the synchronization problem as
described in the section “The Problem: Group Lab Exercise”; and
2. answer the assigned discussion document questions (which are provided in a
separate document).
This assignment is an individual assignment. Whilst you are permitted to discuss this
assignment with other students, the work that you submit must be your own work. You
should not incorporate the work of other students (past or present) into your source code
or discussion document.
You will be required to submit your discussion document to Turnitin for similarity
checking as part of assignment submission. The examiner may use other similarity
checking tools in addition to Turnitin. Your source code may also be checked.
Submit your source code and report to the appropriate submission inboxes in the
COMP3520 Canvas website.
The Problem: Group Lab Exercise
There are N students in the class to do lab exercises. The students are divided into M
groups, each having K students except the last group which may have less than K
students. Each student is assigned to a group with a group id by the teacher.
There is only one lab room and each time it can only hold one group of students. The
students can enter the lab to conduct their lab exercise only when their group id is called
by the teacher. Each group can only do the lab exercise once.
The exercise will be limited to T units of time for each group. (In your program a unit
of time is assumed to be one second.) A group may take a minimum of T/2 units of time
to complete the exercise. After completion, the group will leave the room immediately.
The teacher will call the next group of students to enter the lab after the current group
reports the completion of their exercise and the room becomes empty.
To implement synchronization between the various threads, you may use mutexes, and
condition variables. However, you must not use any other type of synchronization
mechanisms.
You program needs to ask the user to enter the following parameters:
• N: the total number of students in the class;
• K: the number of students in each group; (With N and K, the number of groups
can be determined.)
• T: the time limit for each group to do the exercise.
As mentioned previously, each student thread is assigned a group id by the teacher
thread (not by the main default thread when the student threads are created).
COMP3520 Assignment 1 2020
2
To check whether your program functions properly,
each student thread must print the following status messages wherever appropriate:
• “Student: I am assigned to group [id].”
• “Student in group [id]: My group is called by the teacher and I will enter the lab
now.”
• “Student in group [id]: We have completed our exercise and leave the lab now.”
the teacher thread must print the following status messages wherever appropriate:
• “Teacher: Now I start to assign group id [id] to students.”
• “Teacher: The lab is now available. Students in group [id] can enter the room
and start your lab exercise.”
• “Teacher: Group [id] took [t] units of time to complete the exercise.”
When all students have completed lab exercises, the main thread must print the
following status message and then terminate:
• “Main thread: All students have completed their lab exercises. The simulation
will end now.”
Additional Requirements
Source Code
Your solution must be implemented in the C language. C++ features are not permitted
except those that are part of an official C standard.
Your source code needs to be properly commented and appropriately structured to
allow another programmer who has a working knowledge of C to understand and easily
maintain your code.
You need to include a well-structured and properly commented makefile that allows for
the compilation of your source code using the make command on the School of
Computer Science servers.
Testing and Debugging
You are responsible for testing and debugging your source code.
It is crucial that you ensure that the source code you submit compiles correctly on the
School of Computer Science servers and that the resulting binary functions as intended.
If you submit source code that cannot be compiled on the School servers or if you fail
to make a serious attempt, you may be DISQUALIFIED from this assignment.

Discussion Document
You are required to answer all assigned questions in a separate written document. The
questions and requirements specific to the discussion document will be provided in a
separate document.
COMP3520 Assignment 1 2020
3
Other Matters
Marking criteria for the source code and discussion document will be provided
separately.
To maximize your chances of realizing your full potential in COMP3520, please start
work on this assignment promptly.