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Homework must be submitted electronically to
<csci555@usc.edu>.
It should have a subject of “Homework
2.” You must submit ASCII text without
embedded formatting commands or markup. That means, among other things,
no postscript, no Microsoft Word, no PDF, no FrameMaker, no TeX, no
groff, no DocBook, no HTML, no XML, and no JavaDoc. Do not submit your
homework as an attachment to your e-mail. Do not base 64 encode it. Do
not Rot13 encode it. Plain ASCII text. You may PGP sign it, but are
not required to do so. Do not PGP encrypt it. If you submit something
that is not unmarked-up ASCII, it is functionally the same as turning
nothing in.
Homework turned in on the due date is not penalized, one day late is 25% off (that is the grade will be multiplied by 0.75), 2 days late is 50% off, and 3 days late is 75% off. No work will be accepted more than 3 days late. I will generally use the Date: line of the mail, but should the situation merit it, I am not above looking through mail system logs to confirm the submission time. I should not have to mention it, but forging a Date: line to avoid a late deduction is grounds for an F.
Do the work yourself. Computer science is a collaborative science, and I encourage you to talk over the ideas in the homework with other students. However, the final submission, that is, the text of the homework, must be composed individually by each student. If you hand in homework that is identical to another student, you risk failing the class. (In fact the only way that you would not fail the class in such a circumstance would be if one student had copied another student without the knowledge of the copied student; the copied student would not be penalized.) That is an awfully large risk for 10% of your total grade. Do the work yourself.
As with all work for csci555, this work is subject to the USC code of Student Conduct. Read it, learn it, live it. Should you have any questions on how to apply the code, do not hesitate to contact me or the Office of Student Judicial Affairs and Community Standards. Should it prove possible, do not plagiarize work from sources outside the class. Plagiarizing homework is grounds for failing the class. It is perfectly all right to properly cite external sources, should you find some that are useful.
Answers will not be graded on their beauty of expression. Answers will be graded on whether they show a logical approach and sensible explanation. Short, simple sentences are fine. What is important is that your ideas are clear to the reader, and that they answer the question. Of course, no answer will be penalized because it is beautifully expressed, either.
Each question has equal weight.
1. | In the Li and Hudak paper (ivy) [Li89], Section 5.5 alludes to an algorithm for distributing copy sets, rather than maintaining a centralized list at the owner. Explain why read fault requests do not need to be forwarded to the owner. Explain what messages the new locks at processors holding a read only copy are intended to serialize. |
2. |
Consider a hierarchical naming system that contains
information about classical artists. The hierarchy is
divided by kind of art (painting, sculpture, music, etc.)
and then by artist and finally by the name of the artwork.
You can assume that the designers of the namespace have
appropriately resolved collisions between artists of the
same name and artworks of the same name by the same artist.
One would find the paintings by DaVinci in the directory
This question is just asking about searching for names in the name space, not for content in the art. |
3. | Systems for editing program source often provide search features tuned for that task. For example, by placing the cursor on a function call and pressing a key sequence the editor may reposition the cursor to the definition of that function, even if the function resides in another file. This is an example of a content search system that operates in a narrow context. Explain how such a system would identify function calls and definitions in the source. Explain how such a system would determine what files to include in its search. Explain how the idea of a closure might come into play in identifying the files to include in the search. |
4. | In class there was a discussion about Grapevine's eventual consistency[Birrell82] and the result that an external administrator could not state precisely when a name was added or removed from a group RName. Describe a system where this ability - the ability to know precisely when a name was added or removed from a group - is required and one where it is not. Your explanation should include why the capacity is critical or why not. For your system that requires group removal, do not use a military or associated system. |