ICS 10 • David G. Kay • UC Irvine • Summer 2013

Sixth Homework

This assignment is due by 5:00 on Friday, July 19.

As usual, you'll do parts of this assignment with a partner, someone you haven't worked with on a prevoius assignment. This week, again we need you to send a message to ics10@uci.edu with the names and UCInet IDs of both partners.

Part (a)

Watch the video Sorting Out Sorting, which beautifully illustrates nine different sorting algorithms. Sorting, the activity of putting items into some specified order, is one of the most prevalent tasks in information processing (according to Donald Knuth of Stanford, perhaps America's most famous computer scientist). It's about 30 minutes long; here's a brief viewer's guide:

• There's more detail in this video than you'll be responsible for. We won't ask you about the specific algorithms they describe or about the mathematical characterization of their performance ("n-squared" or "n-log-n"). We would like you to know the basic principle that there can be many different algorithms to do the same task, that those different algorithms can have markedly different performance, and that there's a difference between doing things in a straight line (linearly) and doing them hierarchically (logarithmically) by successively dividing the task into pieces.
• Don't let your concentration waver during the boring parts—that's when the funniest lines come.
• The music is goofy in places. Deal with it.
• The best part of the film comes after the credits, so don't quit when the credits start running.

It wouldn't be fair to expect Dark Knight or Bourne Legacy here; it's a film about algorithms, after all. But it is an excellent example of "information visualization," using graphics effectively to get a point across.

Part (b)

In class we described the (lossless, syntactic) compression method called run-length encoding (RLE). Find three images of flags on the Web: one that will compress very well using RLE, one that will compress very poorly using RLE, and one in the middle. Justify your choices in a few brief sentences (i.e., say why the good one is good, and so on), illustrated with copies of the images. (You'll put your answers to the subsequent parts of the assignment in the same document.)

Part (c)

Below are three images. Image A is the original; the other two are compressed using lossy techniques. One uses reduced quantization; the other uses coarser sampling. Which is which? Give a sentence explaining your answer.

Part (d)

Below are three graphs representing different series of data. Which series would compress best using delta encoding? Which would compress worst? Again, justify your answer in a sentence or two.

Part (e)

(optional) A cryptogram is a message or quotation written in a substitution cipher—for each letter in the original message, a different letter has been uniformly substituted in the cryptogram.

Below is a cryptogram from the Saturday Review. Decode it back into the original English message.

BSL PLXB NFIB CR BSL RDEBDCV DV JFVA VCYLUX DX BSL VCBDEL BSFB BSL ESFIFEBLIX FIL NHILUA DJFKDVFIA. -- RIFVOUDV N. FTFJX

Now ask yourself: What property of natural langauge do cryptograms illustrate? Write your solution to the cryptogram and the one-word answer to this question, marked as part (e) of the document you submit.

Save the document containing your responses to parts (b), (c), (d), and optionally (e) into one document, naming it in the usual form: hw6-jimb-annw. Submit this document via Checkmate. Just one partner should submit one copy; the file name and your Email message will let us give both partners credit.

[Parts (b), (c), and (d) written originally by Eamonn Keough.]