CSCI 340 – Operating Systems Assignment 7 solved




The objective of this assignment is compare the effectiveness (in terms of external fragmentation, number
of probes, and allocation failures) of three different dynamic partitioning placement algorithms (see pages
318-321 in the course textbook). You will be completing the mem.c file and the main.c file. You must
also submit an appropriate Makefile to build this assignment.
A computer systems physical memory will be modeled by an array of unsigned characters. Each element in this array represents a single unit of memory. A value of a zero stored in a element represents
a free unit (i.e. a unit that is not being used). A positive value stored in the element represents a unit in use.
You will be individually simulating each of the three placement algorithms. Each placement algorithm
will be simulated for a specified number of time steps. At each time step a random memory allocation request will be generated of the form, (size, duration) , where size is a random unsigned integer in the range [MIN REQUEST SIZE, MAX REQUEST SIZE] representing the number of contiguous units for this memory allocation request, and duration is a random unsigned character in the range
[MIN DURATION, MIN DURATION] that represents the amount of time this allocated memory will be
in use (see main.c for the definition of these constants).
For each time duration step, the placement algorithm simulation will:
• call mem allocate and gather statistics on number of probes and number of allocation failures.
• call mem single time unit transpired
When the time iteration loop is completed, the external fragmentation value must then be computed using
the mem fragment count function.
On the command line your program will be run with four arguments: 1) size of of physical memory, 2)
number of runs, 3) time steps per run, and 4) random seed used by random number generator. You will be
conducting “number of runs” experiments for each placement algorithm. For each placement algorithm you
will average and display the external fragmentation results, number of probes, and number of allocation
failures. Thus the output will consist of nine different lines.
System and Standard Lib Functions
In this assignment you will choose the system and standard library functions needed to completed the
programming assignment. In short, we want you to make the design and implementation decisions.
Provided Files
The three files listed below are provided to you.
• mem.h: Header file that defines the function prototypes used in this assignment. Please note: You
may not modify or add new function definitions to this header file.
• mem.c: A file that provides the implementation of each function prototype listed in mem.h. You are
required to fully implement all the functions. NOTE: mem init and mem free have been provided.
• main.c: Source code file that includes a stubbed-out main function to be completed by you.
Many comments are provided above each function in the main.c and mem.c files. The provided comments
give detailed instructions that are meant to guide you through this assignment. Please read them carefully
and follow the instructions. For reference purposes, Fig. 1 shows an example snap-shot of the memory
array at some point in time during the simulation.
Figure 1: Example snap-shot of memory array at some point in time.
example snap shot of memory array
Collaboration and Plagiarism
This is an individual assignment, i.e. no collaboration is permitted. Plagiarism will not be tolerated.
Submitted solutions that are very similar (determined by the instructor) will be given a grade of zero. Please
do your own work, and everything will be OK.
Create a compressed tarball, i.e. tar.gz, that only contains the completed main.c , mem.c, and Makefile.
The name of the compressed tarball must be your last name. For example, ritchie.tar.gz would be correct
if the original co-developer of UNIX (Dennis Ritchie) submitted the assignment. Only assignments submitted in the correct format will be accepted (no exceptions). Submit the compressed tarball (via OAKS)
to the Dropbox setup for this assignment. You may resubmit the compressed tarball as many times as you
like, Dropbox will only keep the newest submission.
To be fair to everyone, late assignments will not be accepted. Exceptions will only be made for extenuating
circumstances, i.e. death in the family, health related problems, etc. You will be given a week to complete
this assignment. Poor time management is not excuse. Please do not email assignment after the due date,
it will not be accepted. Please feel free to setup an appointment to discuss the assigned coding problem. I
will be more than happy to listen to your approach and make suggestions. However, I cannot tell you how
to code the solution. Additionally, code debugging is your job. You may use the debugger (gdb) or print
statements to help understand why your solution is not working correctly, your choice.
Grading Rubric
For this assignment the grading rubric is provided in the table shown below.
Program Compiles 10 points
Program Runs with no errors 10 points
main() function implementation 15 points
mem allocate() function implementation 20 points
mem single time unit transpired() function implementation 15 points
mem fragment count() function implementation 20 points
mem clear function implementation 10 points
In particular, the assignment will be graded as follows, if the submitted solution
• does not compile: 0 of 100 points
• compiles but does not run: 10 of 100 points
• compiles and runs with errors: 15 of 100 points
• compiles and runs without errors: 20 of 100 points
• All functions correctly implemented: 100 of 100 points