[Tutor] CPU Scheduling

[alex gonsalez]

Need help trying to implement a CPU scheduling algorithm.I am not even sure
where to start on this. Can someone please guide me and walk me through the
steps for this?

Assignment:
The Simulation.
Simulating the scheduling of a single CPU is a type of discrete event
simulation in which you iterate over discrete steps of time and handle
events as they occur. The simulation continues for a given amount of time
or until all data has been processed.
Add the processes to the ready queue.
 cpu = None
curTime = 0
while ready queue is not empty :
handle events that occur during the current time step curTime = curTime + 1
For this project, the simulation will continue while there are still
processes that need to use the CPU. There are three types of events that
can occur: the CPU is initially empty, the time slice for the current
process on the CPU has expired or the process has completed execution
before the time slice has expired. • If the CPU is initially empty, select
the next process from the ready queue and assign it to the CPU. 1 CS 112 –
Spring 2015 Programming Assignment Four – 2 • If a process completes
execution, it’s removed from the system and it’s total wait time is added
to a running total. • If a process has used its time slice, the process is
removed from the CPU and the next process is selected from the ready queue
and assigned to the CPU. The process that was removed is added back to the
ready queue to wait its turn before it can again use the CPU. Note that the
next process has to be dequeued before the current process is added back to
the queue. Text File. The simulation data will be contained in a text file
that has the following format: 2 15 8 35 0 25 10 5 5 5 2 7 12 30 7 10 0 3 8
15 where each line contains information for a single process. The first
value is the priority and the second value is the amount of processing time
required (i.e. the total amount of time the processor needs to use the
CPU). Note that the lower the priority value, the higher the priority.
Assume the first line contains the information for process 1, the second
line for process 2, and so on. The Algorithms. You are to implement two
priority based scheduling algorithms. For the first algorithm, the next
process selected from the ready queue is simply the one with the highest
priority. For the second algorithm, you are to make a slight modification.
Each time a process is put back into the ready queue, after being removed
from the CPU, reduce the priority level by 5. Results. Your program should
produce output similar to the following: Number of processes: 10 Time
slice: 10 Total time: 150 Algorithm 1 Avg wait time: 60.10 Algorithm 2 Avg
wait time: 62.80 To compute the average wait time over all of the
processes, you will need to keep track of how much time each process spends
in the ready queue and then compute the average of those times. Assume that
all processes are started at the exact same time. CS 112 – Spring 2015
Programming Assignment Four – 3 Requirements. Your program should be placed
within a driver named cpu.py. Your program should be well structured and
commented appropriately as indicated in the programming style guide
provided on the course web page. Some important points to keep in mind: • A
linked list implementation of the Priority Queue ADT is provided in the
course directory. • You must use a top-down design with functions. • Your
program should read from the user the name of the text file that contains
the simulation data and the length of a time slice (as an integer). • Use a
variable (cpu) to hold a reference to the process object (your storage
object) for the process that is currently assigned to the cpu. • In
addition to the curTime variable, you should use a second time variable
that indicates the time when a process needs to be switched off the cpu.
This variable acts as an alarm or the time an alarm goes off to signal an
event. When a process is assigned to the cpu, compute the time when it
should be switched off (current time + time slice or current time + time
remaining for the process). • To compute the wait time, you will need to
keep track of the current time when the process is added to the ready
queue. Then each time a process is removed from the ready queue, compute
how much time it spent in the queue and add that to the processes total
wait time. • You will need to use a storage object to store the information
for a single process. It should contain the process number, the priority,
the remaining CPU time required for that process, its total wait time, and
the time it was added to the ready queue. The data in the storage object
must be stored as integer values. • Each time the process is added back to
the ready queue, you should add the storage objects to the priority queue
and update the remaining CPU time