| author | Christian Urban <christian dot urban at kcl dot ac dot uk> | 
| Fri, 12 Jun 2015 21:56:41 +0100 | |
| changeset 367 | 27e64f2a5369 | 
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<H2>2012/13 MSc Projects</H2>  | 
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<H4>Supervisor: Christian Urban</H4>  | 
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<H4>Email: christian dot urban at kcl dot ac dot uk, Office: Strand Building S1.27</H4>  | 
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<H4>If you are interested in a project, please send me an email and we can discuss details. Please include  | 
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a short description about your programming skills and Computer Science background in your first email.  | 
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Christian Urban <christian dot urban at kcl dot ac dot uk> 
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I will also need your King's username (not student ID) in order to book the project for you. Thanks.</H4>  | 
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<H4>Note that besides being a lecturer in the theoretical part of Computer Science, I am also a passionate  | 
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<A HREF="http://en.wikipedia.org/wiki/Hacker_(programmer_subculture)">hacker</A> …  | 
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defined as “a person who enjoys exploring the details of programmable systems and  | 
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stretching their capabilities, as opposed to most users, who prefer to learn only the minimum  | 
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necessary.” I am always happy to supervise like-minded students.</H4>  | 
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<ul class="striped">  | 
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<li> <H4>[CU1] Regular Expression Matching and Partial Derivatives</H4>  | 
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<p>  | 
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<B>Description:</b>  | 
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<A HREF="http://en.wikipedia.org/wiki/Regular_expression">Regular expressions</A>  | 
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are extremely useful for many text-processing tasks such as finding patterns in texts,  | 
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lexing programs, syntax highlighting and so on. Given that regular expressions were  | 
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introduced in 1950 by <A HREF="http://en.wikipedia.org/wiki/Stephen_Cole_Kleene">Stephen Kleene</A>, you might think  | 
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regular expressions have since been studied and implemented to death. But you would definitely be mistaken: in fact they are still  | 
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an active research area. For example  | 
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<A HREF="http://www.home.hs-karlsruhe.de/~suma0002/publications/ppdp12-part-deriv-sub-match.pdf">this paper</A>  | 
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about regular expression matching and partial derivatives was presented this summer at the international  | 
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PPDP'12 conference. The task in this project is to implement the results from this paper.</p>  | 
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<p>The background for this project is that some regular expressions are  | 
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“<A HREF="http://en.wikipedia.org/wiki/ReDoS#Examples">evil</A>”  | 
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and can “stab you in the back” according to  | 
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this <A HREF="http://tech.blog.cueup.com/regular-expressions-will-stab-you-in-the-back">blog post</A>.  | 
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For example, if you use in <A HREF="http://www.python.org">Python</A> or  | 
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in <A HREF="http://www.ruby-lang.org/en/">Ruby</A> (probably also in other mainstream programming languages) the  | 
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  innocently looking regular expression <code>a?{28}a{28}</code> and match it, say, against the string 
 | 
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<code>aaaaaaaaaaaaaaaaaaaaaaaaaaaa</code> (that is 28 <code>a</code>s), you will soon notice that your CPU usage goes to 100%. In fact,  | 
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Python and Ruby need approximately 30 seconds of hard work for matching this string. You can try it for yourself:  | 
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<A HREF="http://www.dcs.kcl.ac.uk/staff/urbanc/cgi-bin/repos.cgi/afl-material/raw-file/tip/re.py">re.py</A> (Python version) and  | 
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<A HREF="http://www.dcs.kcl.ac.uk/staff/urbanc/cgi-bin/repos.cgi/afl-material/raw-file/tip/re-internal.rb">re.rb</A>  | 
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(Ruby version). You can imagine an attacker  | 
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mounting a nice <A HREF="http://en.wikipedia.org/wiki/Denial-of-service_attack">DoS attack</A> against  | 
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your program if it contains such an “evil” regular expression. Actually  | 
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<A HREF="http://www.scala-lang.org/">Scala</A> (and also Java) are almost immune from such  | 
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attacks as they can deal with strings of up to 4,300 <code>a</code>s in less than a second. But if you scale  | 
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the regular expression and string further to, say, 4,600 <code>a</code>s, then you get a <code>StackOverflowError</code>  | 
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potentially crashing your program.  | 
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</p>  | 
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<p>  | 
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On a rainy afternoon, I implemented  | 
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<A HREF="http://www.dcs.kcl.ac.uk/staff/urbanc/cgi-bin/repos.cgi/afl-material/raw-file/tip/re3.scala">this</A>  | 
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regular expression matcher in Scala. It is not as fast as the official one in Scala, but  | 
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it can match up to 11,000 <code>a</code>s in less than 5 seconds without raising any exception  | 
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(remember Python and Ruby both need nearly 30 seconds to process 28(!) <code>a</code>s, and Scala's  | 
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official matcher maxes out at 4,600 <code>a</code>s). My matcher is approximately  | 
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85 lines of code and based on the concept of  | 
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<A HREF="http://lambda-the-ultimate.org/node/2293">derivatives of regular expressions</A>.  | 
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These derivatives were introduced in 1964 by <A HREF="http://en.wikipedia.org/wiki/Janusz_Brzozowski_(computer_scientist)">  | 
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Janusz Brzozowski</A>, but according to this  | 
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<A HREF="http://www.cl.cam.ac.uk/~so294/documents/jfp09.pdf">paper</A> had been lost in the “sands of time”.  | 
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The advantage of derivatives is that they side-step completely the usual  | 
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<A HREF="http://hackingoff.com/compilers/regular-expression-to-nfa-dfa">translations</A> of regular expressions  | 
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into NFAs or DFAs, which can introduce the exponential behaviour exhibited by the regular  | 
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expression matchers in Python and Ruby.  | 
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</p>  | 
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<p>  | 
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Now the guys from the  | 
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<A HREF="http://www.home.hs-karlsruhe.de/~suma0002/publications/ppdp12-part-deriv-sub-match.pdf">PPDP'12-paper</A> mentioned  | 
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above claim they are even faster than me and can deal with even more features of regular expressions  | 
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(for example subexpression matching, which my rainy-afternoon matcher cannot). I am sure they thought  | 
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about the problem much longer than a single afternoon. The task  | 
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in this project is to find out how good they actually are by implementing the results from their paper.  | 
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Their approach is based on the concept of partial derivatives introduced in 1994 by  | 
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<A HREF="http://reference.kfupm.edu.sa/content/p/a/partial_derivatives_of_regular_expressio_1319383.pdf">Valentin Antimirov</A>.  | 
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I used them once myself in a <A HREF="http://www.inf.kcl.ac.uk/staff/urbanc/Publications/rexp.pdf">paper</A>  | 
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in order to prove the <A HREF="http://en.wikipedia.org/wiki/Myhill–Nerode_theorem">Myhill-Nerode theorem</A>.  | 
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So I know they are worth their money. Still, it would be interesting to actually compare their results  | 
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with my simple rainy-afternoon matcher and potentially “blow away” the regular expression matchers  | 
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in Python and Ruby (and possibly in Scala too).  | 
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</p>  | 
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<p>  | 
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<B>Literature:</B>  | 
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The place to start with this project is obviously this  | 
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<A HREF="http://www.home.hs-karlsruhe.de/~suma0002/publications/ppdp12-part-deriv-sub-match.pdf">paper</A>.  | 
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Traditional methods for regular expression matching are explained  | 
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in the Wikipedia articles  | 
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<A HREF="http://en.wikipedia.org/wiki/DFA_minimization">here</A> and  | 
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<A HREF="http://en.wikipedia.org/wiki/Powerset_construction">here</A>.  | 
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The authoritative <A HREF="http://infolab.stanford.edu/~ullman/ialc.html">book</A>  | 
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on automata and regular expressions is by John Hopcroft and Jeffrey Ullmann (available in the library).  | 
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There is also an online course about this topic by Ullman at  | 
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<A HREF="https://www.coursera.org/course/automata">Coursera</A>, though IMHO not  | 
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done with love.  | 
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Finally, there are millions of other pointers about regular expression  | 
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matching on the Net. Test cases for “<A HREF="http://en.wikipedia.org/wiki/ReDoS#Examples">evil</A>”  | 
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regular expressions can be obtained from <A HREF="http://en.wikipedia.org/wiki/ReDoS#Examples">here</A>.  | 
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</p>  | 
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<p>  | 
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<B>Skills:</B>  | 
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This is a project for a student with an interest in theory and some  | 
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reasonable programming skills. The project can be easily implemented  | 
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in languages like  | 
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<A HREF="http://www.scala-lang.org/">Scala</A>,  | 
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<A HREF="http://en.wikipedia.org/wiki/Standard_ML">ML</A>,  | 
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<A HREF="http://haskell.org/haskellwiki/Haskell">Haskell</A>,  | 
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<A HREF="http://www.python.org">Python</A>, etc.  | 
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</p>  | 
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<li> <H4>[CU2] Automata Theory in Your Web-Browser</H4>  | 
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<p>  | 
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This project is about web-programming (but not in Java):  | 
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There are a number of classic algorithms in automata theory (such as the  | 
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<A HREF="http://hackingoff.com/compilers/regular-expression-to-nfa-dfa">transformation</A> of regular  | 
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expressions into NFAs and DFAs,  | 
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<A HREF="http://en.wikipedia.org/wiki/DFA_minimization">automata minimisation</A>,  | 
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<A HREF="http://en.wikipedia.org/wiki/Powerset_construction">subset construction</A>).  | 
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All these algorithms involve a fair  | 
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amount of calculations, which cannot be easily done by hand. There are a few web applications, typically  | 
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written in <A HREF="http://en.wikipedia.org/wiki/JavaScript">Javascript</A>, that animate these  | 
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calculations, for example <A HREF="http://hackingoff.com/compilers/regular-expression-to-nfa-dfa">this one<A/>.  | 
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But they all have their deficiencies and can be improved with more modern technology.  | 
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An instance is the impressive animation of Phython code found  | 
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<A HREF="http://www.pythontutor.com">here</A>.  | 
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</p>  | 
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<p>  | 
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There now many useful libraries for JavaScript, for example, this  | 
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<A HREF="http://getspringy.com">one</A> for graphs or this  | 
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<A HREF="http://demos.bonsaijs.org/demos/star/index.html">one</A> for graphics.  | 
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There are also  | 
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a number of new programming languages targeting JavaScript, for example  | 
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<A HREF="http://www.typescriptlang.org">TypeScript</A>,  | 
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<A HREF="http://coffeescript.org">CoffeeScript</A>,  | 
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<A HREF="http://www.dartlang.org">Dart</A>,  | 
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<A HREF="http://scriptsharp.com">Script#</A>,  | 
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<A HREF="http://clojure.org">Clojure</A>  | 
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and so on.  | 
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The task in this project is to use a web-programming  | 
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language and suitable library to animate algorithms from automata theory (and also parsing, if wanted).  | 
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This project is for someone who  | 
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want to get to know these new languages.  | 
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</p>  | 
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<B>Literature:</B>  | 
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The same general literature as in [CU1].  | 
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</p>  | 
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<p>  | 
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<B>Skills:</B>  | 
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This is a project for a student with very good programming  | 
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and <A HREF="http://en.wikipedia.org/wiki/Hacker_(programmer_subculture)">hacking</A> skills.  | 
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Some knowledge in JavaScript, HTML and CSS cannot hurt. The algorithms from automata  | 
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theory are fairly standard material.  | 
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</p>  | 
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<!--  | 
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<li> <H4>[CU2] Equivalence Checking of Regular Expressions</H4>  | 
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<p>  | 
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<B>Description:</b>  | 
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Solving the problem of deciding the equivalence of regular expressions can be used  | 
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to decide a number of problems in automated reasoning. Recently,  | 
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<A HREF="http://www.cs.unibo.it/~asperti/">Andreas Asperti</A>  | 
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proposed a simple method for deciding regular expression equivalence described  | 
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<A HREF="http://www.cs.unibo.it/~asperti/PAPERS/compact.pdf">here</A>.  | 
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The task is to implement this method and test it on examples.  | 
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It would be also interesting to see whether Asperti's method applies to  | 
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extended regular expressions, described  | 
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<A HREF="http://ww2.cs.mu.oz.au/~sulzmann/manuscript/reg-exp-partial-derivatives.pdf">here</A>.  | 
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</p>  | 
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<p>  | 
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<B>Literature:</B>  | 
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The central literature is obviously the papers  | 
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<A HREF="http://www.cs.unibo.it/~asperti/PAPERS/compact.pdf">here</A> and  | 
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<A HREF="http://ww2.cs.mu.oz.au/~sulzmann/manuscript/reg-exp-partial-derivatives.pdf">here</A>.  | 
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Asperti has also some slides <A HREF="http://www.cs.unibo.it/~asperti/SLIDES/regular.pdf">here</a>.  | 
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More references about regular expressions can be found  | 
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<A HREF="http://en.wikipedia.org/wiki/Regular_expression">here</A>. Like in  | 
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[CU1], I will give a lot of the background pf this project in  | 
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my Automata and Formal Languages course (6CCS3AFL).  | 
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</p>  | 
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<p>  | 
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<B>Skills:</B>  | 
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This is a project for a student with a passion for theory and some  | 
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reasonable programming skills. The project can be easily implemented  | 
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in languages like Scala  | 
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<A HREF="http://www.scala-lang.org/">Scala</A>,  | 
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<A HREF="http://en.wikipedia.org/wiki/Standard_ML">ML</A>,  | 
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<A HREF="http://haskell.org/haskellwiki/Haskell">Haskell</A>,  | 
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<A HREF="http://www.python.org">Python</A>, etc.  | 
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Being able to read <A HREF="http://haskell.org/haskellwiki/Haskell">Haskell</A>  | 
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code is beneficial for the part involving extended regular expressions.  | 
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</p>  | 
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-->  | 
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<li> <H4>[CU3] Machine Code Generation for a Simple Compiler</H4>  | 
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<p>  | 
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<b>Description:</b>  | 
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Compilers translate high-level programs that humans can read into  | 
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efficient machine code that can be run on a CPU or virtual machine.  | 
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I recently implemented a very simple compiler for a very simple functional  | 
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programming language following this  | 
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<A HREF="http://www.cs.princeton.edu/~dpw/papers/tal-toplas.pdf">paper</A>  | 
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(also described <A HREF="http://www.cs.princeton.edu/~dpw/papers/tal-tr.pdf">here</A>).  | 
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My code, written in <A HREF="http://www.scala-lang.org/">Scala</A>, of this compiler is  | 
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<A HREF="http://www.dcs.kcl.ac.uk/staff/urbanc/compiler.scala">here</A>.  | 
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The compiler can deal with simple programs involving natural numbers, such  | 
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as Fibonacci  | 
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or factorial (but it can be easily extended - that is not the point).  | 
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</p>  | 
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<p>  | 
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While the hard work has been done (understanding the two papers above),  | 
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my compiler only produces some idealised machine code. For example I  | 
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assume there are infinitely many registers. The goal of this  | 
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project is to generate machine code that is more realistic and can  | 
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run on a CPU, like x86, or run on a virtual machine, say the JVM.  | 
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This gives probably a speedup of thousand times in comparison to  | 
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my naive machine code and virtual machine. The project  | 
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requires to dig into the literature about real CPUs and generating  | 
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real machine code.  | 
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</p>  | 
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<p>  | 
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<B>Literature:</B>  | 
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There is a lot of literature about compilers  | 
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(for example <A HREF="http://www.cs.princeton.edu/~appel/papers/cwc.html">this book</A> -  | 
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I can lend you my copy for the duration of the project). A very good overview article  | 
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about implementing compilers by  | 
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<A HREF="http://tratt.net/laurie/">Laurie Tratt</A> is  | 
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<A HREF="http://tratt.net/laurie/tech_articles/articles/how_difficult_is_it_to_write_a_compiler">here</A>.  | 
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An introduction into x86 machine code is <A HREF="http://ianseyler.github.com/easy_x86-64/">here</A>.  | 
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Intel's official manual for the x86 instruction is  | 
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<A HREF="http://download.intel.com/design/intarch/manuals/24319101.pdf">here</A>.  | 
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A simple assembler for the JVM is described <A HREF="http://jasmin.sourceforge.net">here</A>.  | 
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An interesting twist of this project is to not generate code for a CPU, but  | 
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for the intermediate language of the <A HREF="http://llvm.org">LLVM</A> compiler  | 
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(also described <A HREF="https://wiki.aalto.fi/display/t1065450/LLVM+IR">here</A> and  | 
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<A HREF="http://llvm.org/docs/LangRef.html">here</A>). If you want to see  | 
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what machine code looks like you can compile your C-program using gcc -S.  | 
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</p>  | 
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<p>  | 
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<B>Skills:</B>  | 
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This is a project for a student with a deep interest in programming languages and  | 
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compilers. Since my compiler is implemented in <A HREF="http://www.scala-lang.org/">Scala</A>,  | 
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it would make sense to continue this project in this language. I can be  | 
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of help with questions and books about <A HREF="http://www.scala-lang.org/">Scala</A>.  | 
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But if Scala is a problem, my code can also be translated quickly into any other  | 
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language.  | 
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</p>  | 
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<li> <H4>[CU4] Implementation of Register Spilling Algorithms</H4>  | 
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<p>  | 
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<b>Description:</b>  | 
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This project is similar to [CU3]. The emphasis here, however, is on the  | 
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implementation and comparison of register spilling algorithms, also often called register allocation  | 
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algorithms. They are part of any respectable compiler. As said  | 
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in [CU3] my simple compiler lacks them and assumes an infinite amount of registers instead.  | 
| 154 | 301  | 
Real CPUs however only provide a fixed amount of registers (for example  | 
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x86-64 has 16 general purpose registers). Whenever a program needs  | 
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to hold more values than registers, the values need to be “spilled”  | 
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into the main memory. Register spilling algorithms try to minimise  | 
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this spilling, since fetching values from main memory is a costly  | 
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operation.  | 
|
307  | 
</p>  | 
|
308  | 
||
309  | 
<p>  | 
|
310  | 
The classic algorithm for register spilling uses a  | 
|
311  | 
<A HREF="http://en.wikipedia.org/wiki/Register_allocation">graph-colouring method</A>.  | 
|
312  | 
However, for some time the <A HREF="http://llvm.org">LLVM</A> compiler  | 
|
313  | 
used a supposedly more efficient method, called the linear scan allocation method  | 
|
314  | 
(described  | 
|
315  | 
<A HREF="http://www.cs.ucla.edu/~palsberg/course/cs132/linearscan.pdf">here</A>).  | 
|
316  | 
However, it was later decided to abandon this method in favour of  | 
|
317  | 
a <A HREF="http://blog.llvm.org/2011/09/greedy-register-allocation-in-llvm-30.html">  | 
|
318  | 
greedy register allocation</A> method. It would be nice if this project can find out  | 
|
319  | 
what the issues are with these methods and implement at least one of them for the  | 
|
320  | 
simple compiler referenced in [CU3].  | 
|
321  | 
</p>  | 
|
322  | 
||
323  | 
<p>  | 
|
324  | 
<B>Literature:</B>  | 
|
325  | 
The graph colouring method is described in Andrew Appel's  | 
|
326  | 
<A HREF="http://www.cs.princeton.edu/~appel/modern/java/">book</A> on compilers  | 
|
327  | 
(I can give you my copy of this book, if it is not available in the library).  | 
|
328  | 
There is also a survey  | 
|
329  | 
<A HREF="http://compilers.cs.ucla.edu/fernando/publications/drafts/survey.pdf">article</A>  | 
|
330  | 
about register allocation algorithms with further pointers.  | 
|
331  | 
</p>  | 
|
332  | 
||
333  | 
<p>  | 
|
334  | 
<B>Skills:</B>  | 
|
335  | 
Same skills as [CU3].  | 
|
336  | 
</p>  | 
|
337  | 
||
338  | 
<li> <H4>[CU5] A Student Polling System</H4>  | 
|
339  | 
||
340  | 
<p>  | 
|
341  | 
<B>Description:</B>  | 
|
342  | 
One of the more annoying aspects of giving a lecture is to ask a question  | 
|
343  | 
to the students and no matter how easy the questions is to not  | 
|
344  | 
receive an answer. Recently, the online course system  | 
|
345  | 
<A HREF="http://www.udacity.com">Udacity</A> made an art out of  | 
|
346  | 
asking questions during lectures (see for example the  | 
|
347  | 
<A HREF="http://www.udacity.com/overview/Course/cs253/CourseRev/apr2012">Web Application Engineering</A>  | 
|
348  | 
course CS253).  | 
|
349  | 
The lecturer there gives multiple-choice questions as part of the lecture and the students need to  | 
|
350  | 
click on the appropriate answer. This works very well in the online world.  | 
|
351  | 
For “real-world” lectures, the department has some  | 
|
352  | 
<A HREF="http://en.wikipedia.org/wiki/Audience_response">clickers</A>  | 
|
353  | 
(these are little devices part of an audience response systems). However,  | 
|
354  | 
they are a logistic nightmare for the lecturer: they need to be distributed  | 
|
355  | 
during the lecture and collected at the end. Nowadays, where students  | 
|
356  | 
come with their own laptop or smartphone to lectures, this can  | 
|
357  | 
be improved.  | 
|
358  | 
</p>  | 
|
359  | 
||
360  | 
<p>  | 
|
361  | 
The task of this project is to implement an online student  | 
|
362  | 
polling system. The lecturer should be able to prepare  | 
|
363  | 
questions beforehand (encoded as some web-form) and be able to  | 
|
364  | 
show them during the lecture. The students  | 
|
365  | 
can give their answers by clicking on the corresponding webpage.  | 
|
366  | 
The lecturer can then collect the responses online and evaluate them  | 
|
367  | 
immediately. Such a system is sometimes called  | 
|
368  | 
<A HREF="http://en.wikipedia.org/wiki/Audience_response#Smartphone_.2F_HTTP_voting">HTML voting</A>.  | 
|
369  | 
There are a number of commercial  | 
|
370  | 
solutions for this problem, but they are not easy to use (in addition  | 
|
371  | 
to being ridiculously expensive). A good student can easily improve upon  | 
|
372  | 
what they provide.  | 
|
373  | 
</p>  | 
|
374  | 
||
375  | 
<p>  | 
|
376  | 
The problem of student polling is not as hard as  | 
|
377  | 
<A HREF="http://en.wikipedia.org/wiki/Electronic_voting">electronic voting</A>,  | 
|
378  | 
which essentially is still an unsolved problem in Computer Science. The  | 
|
379  | 
students only need to be prevented from answering question more than once thus skewing  | 
|
380  | 
any statistics. Unlike electronic voting, no audit trail needs to be kept  | 
|
381  | 
for student polling. Restricting the number of answers can probably be solved  | 
|
| 163 | 382  | 
by setting appropriate cookies on the students'  | 
| 154 | 383  | 
computers or smart phones.  | 
384  | 
</p>  | 
|
385  | 
||
386  | 
<p>  | 
|
| 163 | 387  | 
However, there is one restriction that makes this project harder than it seems  | 
| 165 | 388  | 
at first sight: The department does not allow large server applications and databases  | 
389  | 
to be run on calcium, which is the central server in the department. So the problem  | 
|
390  | 
should be solved with as few resources as possible  | 
|
391  | 
on the “back-end” collecting the votes.  | 
|
| 163 | 392  | 
</p>  | 
393  | 
||
394  | 
<p>  | 
|
| 154 | 395  | 
<B>Literature:</B>  | 
396  | 
The project requires fluency in a web-programming language (for example  | 
|
| 164 | 397  | 
<A HREF="http://en.wikipedia.org/wiki/JavaScript">JavaScript</A>,  | 
| 154 | 398  | 
<A HREF="http://en.wikipedia.org/wiki/PHP">PHP</A>,  | 
399  | 
Java, <A HREF="http://www.python.org">Python</A>,  | 
|
400  | 
<A HREF="http://en.wikipedia.org/wiki/Go_(programming_language)">Go</A>,  | 
|
401  | 
<A HREF="http://www.scala-lang.org/">Scala</A>,  | 
|
| 163 | 402  | 
<A HREF="http://en.wikipedia.org/wiki/Ruby_(programming_language)">Ruby</A>).  | 
| 154 | 403  | 
For web-programming the  | 
404  | 
<A HREF="http://www.udacity.com/overview/Course/cs253/CourseRev/apr2012">Web Application Engineering</A>  | 
|
405  | 
course at <A HREF="http://www.udacity.com">Udacity</A> is a good starting point  | 
|
406  | 
to be aware of the issues involved. This course uses <A HREF="http://www.python.org">Python</A>.  | 
|
407  | 
To evaluate the answers from the student, Google's  | 
|
408  | 
<A HREF="https://developers.google.com/chart/image/docs/making_charts">Chart Tools</A>  | 
|
| 164 | 409  | 
might be useful, which are also described in this  | 
| 154 | 410  | 
<A HREF="http://www.youtube.com/watch?v=NZtgT4jgnE8">youtube</A> video.  | 
411  | 
</p>  | 
|
412  | 
||
413  | 
<p>  | 
|
414  | 
<B>Skills:</B>  | 
|
| 163 | 415  | 
This project needs very good web-programming skills. A  | 
| 154 | 416  | 
<A HREF="http://en.wikipedia.org/wiki/Hacker_(programmer_subculture)">hacker mentality</A>  | 
417  | 
(see above) is probably very beneficial: web-programming is an area that only emerged recently and  | 
|
418  | 
many tools still lack maturity. You probably have to experiment a lot with several different  | 
|
419  | 
languages and tools.  | 
|
420  | 
</p>  | 
|
421  | 
||
422  | 
<li> <H4>[CU6] Implementation of a Distributed Clock-Synchronisation Algorithm developed at NASA</H4>  | 
|
423  | 
||
424  | 
<p>  | 
|
425  | 
<B>Description:</B>  | 
|
426  | 
There are many algorithms for synchronising clocks. This  | 
|
427  | 
<A HREF="http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120000054_2011025573.pdf">paper</A>  | 
|
| 164 | 428  | 
describes a new algorithm developed by NASA for clocks that communicate by exchanging  | 
| 154 | 429  | 
messages and thereby reach a state in which (within some bound) all clocks are synchronised.  | 
430  | 
A slightly longer and more detailed paper about the algorithm is  | 
|
431  | 
<A HREF="http://hdl.handle.net/2060/20110020812">here</A>.  | 
|
| 164 | 432  | 
The point of this project is to implement this algorithm and simulate a networks of clocks.  | 
| 154 | 433  | 
</p>  | 
434  | 
||
435  | 
<p>  | 
|
436  | 
<B>Literature:</B>  | 
|
| 164 | 437  | 
There is a wide range of literature on clock synchronisation algorithms.  | 
| 154 | 438  | 
Some pointers are given in this  | 
439  | 
<A HREF="http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120000054_2011025573.pdf">paper</A>,  | 
|
440  | 
which describes the algorithm to be implemented in this project. Pointers  | 
|
441  | 
are given also <A HREF="http://en.wikipedia.org/wiki/Clock_synchronization">here</A>.  | 
|
442  | 
</p>  | 
|
443  | 
||
444  | 
<p>  | 
|
445  | 
<B>Skills:</B>  | 
|
446  | 
In order to implement a simulation of a network of clocks, you need to tackle  | 
|
447  | 
concurrency. You can do this for example in the programming language  | 
|
448  | 
<A HREF="http://www.scala-lang.org/">Scala</A> with the help of the  | 
|
449  | 
<A HREF="http://akka.io">Akka</a> library. This library enables you to send messages  | 
|
450  | 
between different <I>actors</I>. <A HREF="http://www.scala-lang.org/node/242">Here</A>  | 
|
451  | 
are some examples that explain how to implement exchanging messages between actors.  | 
|
452  | 
</p>  | 
|
453  | 
||
| 
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454  | 
<li> <H4>[CU7] An Infrastructure for Dispalying and Animating Code in a Web-Browser</H4>  | 
| 
 
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 | 
455  | 
|
| 
 
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456  | 
<p>  | 
| 
 
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457  | 
<B>Description:</B>  | 
| 
 
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 | 
458  | 
The project aim is to implement an infrastructure for displaying and  | 
| 
 
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 | 
459  | 
animating code in a web-browser. The infrastructure should be agnostic  | 
| 
 
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460  | 
with respect to the programming language, but should be configurable.  | 
| 
 
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461  | 
Something smaller than projects such as <A HREF="http://www.pythontutor.com">here</A>,  | 
| 
 
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 | 
462  | 
<A HREF="http://ideone.com">here</A>,  | 
| 
 
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 | 
463  | 
<A HREF="http://codepad.org">here</A>,  | 
| 
 
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464  | 
<A HREF="http://www.w3schools.com/html/tryit.asp?filename=tryhtml_intro">here</A>  | 
| 
 
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465  | 
|
| 
 
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 | 
466  | 
</p>  | 
| 
 
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467  | 
|
| 154 | 468  | 
</ul>  | 
469  | 
</TD>  | 
|
470  | 
</TR>  | 
|
471  | 
</TABLE>  | 
|
472  | 
||
473  | 
<P>  | 
|
474  | 
<!-- Created: Tue Mar 4 00:23:25 GMT 1997 -->  | 
|
475  | 
<!-- hhmts start -->  | 
|
476  | 
Last modified: Wed Sep 12 16:30:03 GMT 2012  | 
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477  | 
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478  | 
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