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日期:2020-12-04 08:23

COMP2046 Coursework Autumn 2020
Weight: 25% module marks
Deadline: 14th December 2020, 12:00 China time.
Submission: Create a single .zip file containing your source code files. We will need to rebuild
your code to test your implementation. You should submit your single zip file through moodle.
Overview
The goal of this coursework is to make use of operating system APIs (specifically, the POSIX
API in Linux) and simple concurrency directives to implement simple shared memory problem
and scheduling algorithm with a producer- consumer modle.
To maximise your chances of completing this coursework successfully, and to give you the
best chance to get a good mark, the coursework is divided into multiple independent
components, each one gradually more difficult to implement. The individual solutions should
then be used/extended into the final program, which combines the principles of the individual
programs. Completing this coursework successfully will give a good understanding of:
? Basic process creation, memory image overwriting and shared memory usage.
? Basic process scheduling algorithms and evaluation criteria.
? The use operating system APIs in Linux.
? Critical sections and the need to implement mutual exclusion.
? The basics of concurrent/parallel programming using an operating system’s facilities
(e.g. semaphores, mutex).
Submission requirements
You are asked to rigorously stick to the naming conventions for your source code and output
files. The source files must be named TASKX.c, any output files should be named
TASKX.txt, with X being the number of the task. Ignoring the naming conventions above
will result in you loosing marks.
For submission, create a single .zip file containing all your source code and output files in one
single directory (i.e., create a directory first, place the files inside the directory, and zip up the
directory). Please use your username as the name of the directory.
Copying Code and Plagiarism ?
You may freely copy and adapt any code samples provided in the lab exercises or lectures.
You may freely copy code samples from the Linux/POSIX websites, which has many examples
explaining how to do specific tasks. This coursework assumes that you will do so and doing so
is a part of the coursework. You are therefore not passing someone else’s code off as your
own, thus doing so does not count as plagiarism. Note that some of the examples provided
omit error checking for clarity of the code. You are required to add error checking wherever
necessary.
You must not copy code samples from any other source, including another student on this or
any other course, or any third party. If you do so then you are attempting to pass someone
else’s work off as your own and this is plagiarism. The University takes plagiarism extremely
seriously and this can result in getting 0 for the coursework, the entire module, or potentially
much worse.
Getting Help
You MAY ask Dr Qian Zhang and Dr Saeid Pourroostaei Ardakani for help in understanding
coursework requirements if they are not clear (i.e. what you need to achieve). Any necessary
clarifications will then be added to the Moodle page so that everyone can see them.
You may NOT get help from anybody else to actually do the coursework (i.e. how to do it),
including ourselves. You may get help on any of the code samples provided, since these are
designed to help you to do the coursework without giving you the answers directly.
Background Information
All code should be implemented in C and tested/run on the school’s Linux servers. When you
compile your program using gcc, please do not forget to use the –pthread option to suppress
the semaphore related compilation messages.
Please note that if you use sem_init to create a semaphore, it will not work in Mac OS
unfortunately but it should work on most linux systems. It certainly works fine on the school
linux server.
Additional information on programming in Linux, the use of POSIX APIs, and the specific use
of threads and concurrency directives in Linux can be found, e.g., here (it is my
understanding that this book was published freely online by the authors and that there are
no copyright violations because of this).
Coding and Compiling Your Coursework
You are free to use a code editor of your choice, but your code MUST compile and run on the
school’s Linux servers. It will be tested and marked on these machines.
There are several source files available on Moodle for download that you must use. To ensure
consistency across all students, changes are not to be made on these given source files. The
header file (coursework.h, linkedlist.h) contain a number of definitions of
constants and several function prototypes. The source file (coursework.c,
linkedlist.c) contain the implementation of these functions. Documentation is included
in both files and should be self-explanatory. Note that, in order to use these files with your
own code, you will be required to specify the file on the command line when using the gcc
compiler (e.g. “gcc –std=c99 TASKX.c coursework.c linkedlist.c”), and include the
coursework.h/linkedlist.c file in your code (using #include
“coursework.h”/ #include “linkedlist.h”).
Apart from the number setting defined in coursework.h, you are not allowed to change
anything in the given source/header files. Code cannot be successfully compiled on school’s
linux servers with given source/header files will receive ZERO marks.
Task 1: Static Process Scheduling (40 marks):
The goal of this task it to implement two basic process scheduling algorithms (Shortest Job
First (SJF) and Priority Queues (PQ)) in a static environment. That is, all jobs are known at the
start. You are expected to calculate response and turnaround times for each of the processes,
as well as averages for all jobs. Note that the priority queue algorithm uses a Round Robin
(RR) within the priority levels.
Both algorithms should be implemented in separate source files (TASK1a.c for SJF,
TASK1b.c for PQ) and use the linked list implementation provided in (linkedlist.c
and linkedlist.h) for the underlying data structure. In both cases, your implementation
should contain a function that generates a pre-defined NUMBER_OF_PROCESSES (this
constant is defined in coursework.h) and stores them in a linked list (using a SJF approach
for Task1a and RR for Task1b). This linked list simulates a ready queue in a real operating
system. The implementation of the SJF and PQ will remove jobs from the ready queues in the
order in which they should run. Note that you are expected to use multiple linked lists for the
PQ algorithm, one for each priority level. In the linked list ready queue implementation, the
process will be added to the end and removed from the front.
You must use the coursework source and header file provided on Moodle (linkedlist.c,
linkedlist.h, coursework.c and coursework.h). The header file contains a
number of definitions of constants, a definition of a simple process control block, and several
function prototypes. The source file (coursework.c) contains the implementation of these
function prototypes and must be specified on the command line when compiling your code.
In order to make your code/simulation more realistic, a runNonPreemptiveJob()and a
runPreemptiveJob() function are provided in the coursework.c file. These
functions simulate the processes running on the CPU for a certain amount of time, and update
their state accordingly. The respective functions must be called every time a process runs.
The criteria used in the marking TASK1a.c and TASK1b.c of your coursework include:
? Whether you submitted code, the code compiles, the code runs.
? Your code must compile using gcc –std=c99 TASK1a/b.c linkedlist.c
coursework.c on the school’s linux servers.
? The code to generate a pre-defined number of processes and store them in a linked
list corresponding to the queue in a SJF fashion.
? Whether jobs are added at the end of the linked list in an efficient manner, that is by
using the tail of the linked list rather than traversing the entire linked list first.
? Whether the correct logic is used to calculate (average) response and (average)
turnaround time for both algorithms. Note that both are calculated relative to the
time that the process was created (which is a data field in the process structure).
? Whether the implementation of the SJF and PQ algorithms is correct.
? Correct use of the appropriate run functions to simulate the processes running on the
CPU.
? The correct use of dynamic memory and absence memory leaks. That means, your
code correctly frees the elements in the linked list and its data values.
? Code to that visualises the working of the algorithms and that generates output similar
to the example provided on Moodle.
For this task, you are required to submit three files: TASK1a.c and TASK1b.c
Task 2: Dynamic Process Creation/Consumption (60 marks)
In task 1, we assumed that all processes are available upon start-up. This is usually not the
case in real world systems, nor can it be assumed that an infinite number of processes can
simultaneously co-exist in an operating system.
Therefore, you are asked to implement the process scheduling algorithms from task 1 (SJF
and PQ) using a bounded buffer with multiple producer and consumer solution to simulate
how an Operating System performs process scheduling. In this design, the size models the
maximum number of processes that can co-exist in the system is fixed by buffer size, there
are multiple dispatchers (producer) add processes to the ready queue while multiple CPUs
(consumer) select processes to run simultaneously. To do this, you have to extend the code
tasks 1a and 1b to a bounded buffer with multiple producer/consumer solution. Similarly to
task 1, both solutions should be implemented in separate source files (TASK2a.c for SJF,
and TASK2b.c for PQ).
In both cases (SJF and PQ), the bounded buffers must be implemented as a linked list. In the
case of SJF, the maximum number of elements in the list should not exceed N, where N is
equal to the maximum co-exist process number defined by MAX_BUFFER_SIZE (defined in
coursework.h). In the case of the PQs, the maximum number of elements across all
queues (every priority level is represented by a separate linked list) should not exceed
MAX_BUFFER_SIZE. The producers generate process and adds them to the end of the
bounded buffer. The consumers will remove process from the start of the list and simulate
them “running” on the CPU (using the runNonPreemptiveJob()(SJF) and
runPreemptiveJob()(PQ) functions provided in the coursework.c file).
In the case of Priority Queues, jobs that have not fully completed in the ‘’current run’’ (i.e.
the remaining time was larger than the time slice) must be added to the end of the relevant
queue/buffer again. Note that at any one point in time, there shouldn’t be more than
MAX_BUFFER_SIZE jobs in the system (that is, the total number of processes currently
running or waiting in the ready queue(s)).
The final version of your code should include:
? A linked list (or set of linked lists for PQs) of jobs representing the bounded buffer
utilised in the correct manner. The maximum size of this list should be configured to
not exceed, e.g., 50 elements.
? Multiple producer threads that generate a total number of MAX_NUMBER_OF_JOBS
processes, and not more. That is, the number of elements produced by the different
threads sums up to MAX_NUMBER_OF_JOBS. Elements are added to the buffer as
soon as free spaces are available. A consumer function that removes elements from
the end of the buffer (one at a time).
? A mechanism to ensure that all consumers terminate gracefully when
MAX_NUMBER_OF_JOBS have been consumed. The code to:
o Declare all necessary semaphores/mutexes and initialise them to the correct
values.
o Create the producer/consumer threads.
o Join all threads with the main thread to prevent the main thread from finishing
before the consumers/producers have ended.
o Calculate the average response time and average turnaround time and print
them on the screen when all jobs have finished.
o Synchronise all critical sections in a correct and efficient manner, and only
when strictly necessary keeping the critical sections to the smallest possible
code set(s).
o Generate output similar in format to the example provided on Moodle for this
requirement (for 100 jobs, using a buffer size of 10).
The criteria used in the marking TASK2a.c and TASK2b.c of your coursework include:
? Whether you have submitted the code and you are using the correct naming
conventions and format.
? Your code must compile using gcc –std=c99 TASK2a/b.c linkedlist.c
coursework.c –pthread on the school’s linux servers.
? Whether the code compiles correctly, and runs in an acceptable manner.
? Whether you utilise and manipulate your linked list in the correct manner.
? Whether semaphores/mutexes are correctly defined, initialised, and utilised.
? Whether consumers and producers are joined correctly.
? Whether the correct number of producers and consumers has been utilised, as
specified in the coursework description.
? Whether consumers and producers end gracefully/in a correct manner.
? Whether consumers/producers have been assigned a unique id (as can be seen from
the output provided on Moodle).
? Whether the exact number of processes is produced and consumed.
? Whether the calculation of (average) response and (average) turnaround time remain
correct.
? Whether the integration of SJF/PQ is correct for the bounded buffer problem.
? Whether your code is efficient, easy to understand, and allows for maximum
parallelism.
? Whether your code runs free of deadlocks.
? Whether the output generated by your code follows the format of the examples
provided on Moodle.
For this task, you are required to submit three files: TASK2a.c and TASK2b.c

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