CSCE 311
Fall 2008
Project # 3
Assigned: Sept. 23, 2008
Due: Oct. 2th, 2008 (timestamp must be earlier than lecture time)
Objective: To implement Thread scheduling on the OSP2 simulator. You will implement
the module ThreadCB.java to further your understanding of CPU scheduling. You
are required to implement a multi-level queue that uses the round-robin scheduling
algorithm.
Required to turn in: Follow all directions regarding hand-in procedures. Points will be
deducted if you do not follow directions precisely. You must turn in a hard copy of the
ThreadCB.java code you implemented. You must also provide a hard copy of one
run (i.e. osp.log) using the multi-level queue scheduling algorithm described
in this document. You must also submit an electronic copy of your multi-level
queue solution (or your best try) via dropbox. Late assignments will not be accepted.
You must document your code and provide a one-page explanation of how you
accomplished the assignment (or what you have currently and why you could not
complete). You should describe your use, creation, and manipulation of data structures to
accomplish the assignment.
Building and executing the simulation
I suggest that you create a new directory and copy your files from the first part of the cpu
scheduling project and starting with that version of ThreadCB.java modify it to
create the multi-level queue solution. The only file you should have to modify is
ThreadCB.java. Modifying the other files will probably "break" OSP2.
The only changes you need to make to your code from the previous project are:
1) Create a multi-level queue that consists of two separate queues; a high priority
queue and a lower priority queue. (You will need two separate queues.) The high
priority queue will use round-robin scheduling with a quantum value of 20.
The lower priority queue will use round-robin scheduling with a quantum
value of 150.
2) Each time you insert a thread into the multi-level ready queue, you will estimate
the cpu burst time using exponential averaging (τn = αtn-1 + (1-α)τn-1). Use an
alpha value of 0.9, i.e., τn=0.9tn-1+0.1τn-1 . To make this work you will need to
keep track of the last cpu burst for the thread. You will also need to keep track of
the last estimate of the burst time. Do this by adding two additional variables to
the ThreadCB class:
a. int lastCpuBurst (this is tn-1 in the equation)
b. int estimatedBurstTime (this is τ in the equation)
c. long lastDispatch (you need this to compute lastCpuBurst)
When you first create a thread you should initialize these variables to -1. When
you estimate the cpu burst for a new process, there are no previous values of tn-1
and τn-1 that you can use. Instead simply set τn = 20 the quantum for the high
