CS 6/73201 Advanced Operating Systems
	      Project #2

Due: - final submission to Tom via e-mail by 11:59pm on Tuesday,
       October 23, 2007
     - correctness verification description to Mikhail and Tom 
       via e-mail by 11:59pm on Tuesday, October 9, 2007


In this project you are to implement two algorithms that we study in
class. The algorithm assignment is as follows.


Alam, Najla	     	Tarry's and Awerbuch spanning tree 
                        construction algorithms
Hardas, Manas Sudhakar	Lamport's scalar clocks, 
                        Singhal-Kshemkalyani's implementation of vector clocks
Mali, Amitkumar A	Ho-Ramammorthy 2 phase snapshot algorithm
			Chandy-Misra snapshot algorithm
Malik, Rizwan		Dijkstra-Scholten and Shavit-Francez termination
			algorithms
Lee, Victor E		Rikart-Agrawala and Maekawa distributed mutual
			exclusion algorithms
Panchariya, Sagar	Raymond and Suzuki-Kasami mutual exclusion algorithms
Sehgal, Rahul		Christian's and Berkeley time 
			synchronization algorithms
Yuan, Man		Birman-Schiper-Stephenson causal ordering of broadcasts
			Schiper-Eggli-Sandoz causal ordering of messages

We may not be able to study the algorithms in class in time for you to
implement them. Thus, I suggest you read the relevant material in
advance. As a starting point, I made the presentation slides that deal
with these algorithms available on the course's webpage. Note that
these slides may not be sufficient for good understating of your
algorithms.  You may have to go to the textbook and to the original
papers describing the algorithms.

Note that the slides are for reference purposes only, I may change
them as I prepare for classes.


CORRECTNESS VERIFICATION DESCRIPTION 

It is your responsibility to convince us that your algorithm works as
expected. As the first step, you have to prepare a one-page
description as to how you are planning to do so for each of your
algorithm. This description is to be submitted to Mikhail and Tom by
the date indicated above. Note that you may want to submit this
description earlier so that you will get feedback from us and start
working on the actual algorithm implementation. Find below an example
of such description.

Note that this description is not final, and you may decide to change
what you will be submitting at a later time. Treat it as a guideline.


CODING, SUBMITTING THE PROJECT

Your submission in part will be judged on elegance, efficiency and
clarity of your code. So make sure that the programs you write are of
high quality.  Code without comments will be substantially penalized.

The final project is to be submitted as a tar-archive to Tom by e-mail
by the date indicated above.  If it works, submit evidence of correct
execution. In evidence, submit the expanded correctness verification
description and actual run-time sequences (with inserted commentaries
if necessary) of correct execution. Note that at this point we are not
looking for exhaustive quality analysis. A few representative examples
would suffice. Note, however, that the examples should be diverse
enough to convince us that your code indeed completely implements the
specification of the original algorithm.

If the code does not work -- submit your explanation as to why you
think it does not and how it may be fixed. Note that is is always
better to submit  working code a few days late than a non-working
project on time. Also, bear in mind that your third project will
depend on you finishing your second project.


CODE VERIFICATION DESCRIPTION EXAMPLE

I am planning to implement the Wave Tree Traversal Algorithm. To show
that it works correctly, I am planning to test it on several different
tree topologies. Specifically, I will select: a star of eight nodes, a
chain of eight nodes and a more generic topology similar to what we
used in class.

To document correct runs I will make each node print out a debug
statement every time it gets a token and when it decides.  In the
debug statement, I will have the node print its identifier, the
contents of its, "rec" array and its next action (if it will forward
the token, decide or wait)

To ensure that my algorithm accommodates arbitrary computations, I'll
have each node wait random time (in the range from 0 to 2 seconds)
before proceeding with the next action. For the generic topology I
will record a computation where a leaf and a non-leaf node decides.

For the final project submission, I will submit the one run for the
star topology, one -- for the chain topology, and two for the generic
topology (one where leaf decides and one where only non-leaves decide).