MetaFilter posts tagged with CS
http://www.metafilter.com/tags/CS
Posts tagged with 'CS' at MetaFilter.Mon, 04 Aug 2014 07:09:11 -0800Mon, 04 Aug 2014 07:09:11 -0800en-ushttp://blogs.law.harvard.edu/tech/rss60The Visual Microphone: Passive Recovery of Sound from Video
http://www.metafilter.com/141621/The%2DVisual%2DMicrophone%2DPassive%2DRecovery%2Dof%2DSound%2Dfrom%2DVideo
Researchers at the MIT Computer Science and Artificial Intelligence Laboratory, Microsoft Research, and Adobe Research have <a href="http://people.csail.mit.edu/mrub/VisualMic/">presented a technique</a> for reconstructing an audio signal by analyzing minute vibrations of objects depicted in video. For example, the method can be used to extract intelligible speech from video of a bag of potato chips filmed from 15 feet away through soundproof glass. <a href="https://www.youtube.com/watch?v=FKXOucXB4a8">Direct YouTube link to the video</a>. <a href="http://newsoffice.mit.edu/2014/algorithm-recovers-speech-from-vibrations-0804">MIT News article</a>.
A modification of the technique allowed for less accurate but still impressive results from video taken with a normal dSLR rather than a high speed camera.
The technique is related to previous work by Hao-Yu Wu, Michael Rubinstein, et al. on <a href="http://people.csail.mit.edu/mrub/vidmag/">Eulerian Video Magnification</a>, <a href="http://www.metafilter.com/116608/Eulerian-Video-Magnification">previously on MetaFilter</a>. tag:metafilter.com,2014:site.141621Mon, 04 Aug 2014 07:09:11 -0800jedicusMetaFilter​FrontPage​BlogPost​TitleContent​String
http://www.metafilter.com/138422/MetaFilterFrontPageBlogPostTitleContentString
Two of these Java class names from the <a href="https://github.com/spring-projects/spring-framework">Spring</a> framework are made up. One of them is real. <a href="http://java.metagno.me/">Can you guess the real one?</a> tag:metafilter.com,2014:site.138422Fri, 18 Apr 2014 09:51:15 -0800schmodCS in VN
http://www.metafilter.com/126450/CS%2Din%2DVN
<a href="http://neil.fraser.name/news/2013/03/16/">Kids In Vietnam Are Crazy Good At Programming</a> - '11th graders in Vietnam are so good at programming that they could easily pass an interview at Google' <small>(<a href="http://blog.digg.com/post/46251309499/whats-next">via</a>)</small> tag:metafilter.com,2013:site.126450Wed, 27 Mar 2013 22:49:31 -0800kliuless24/7 de_dust, AWP disabled
http://www.metafilter.com/122183/247%2Ddedust%2DAWP%2Ddisabled
<a href="http://www.johnsto.co.uk/design/making_dust">The making of de_dust</a> & <a href="http://www.johnsto.co.uk/design/making_dust2">de_dust2</a>. tag:metafilter.com,2012:site.122183Sun, 25 Nov 2012 09:24:41 -0800EvernixLearnable Programming
http://www.metafilter.com/120325/Learnable%2DProgramming
Bret Victor: We often think of a programming environment or language in terms of its features -- this one "has code folding", that one "has type inference". This is like thinking about a book in terms of its words -- this book has a "fortuitous", that one has a "munificent". What matters is not individual words, but how the words together convey a message.
Likewise, a well-designed programing system is not simply a bag of features. A good system is designed to encourage particular ways of thinking, with all features carefully and cohesively designed around that <a href="http://worrydream.com/LearnableProgramming/">purpose</a>. tag:metafilter.com,2012:site.120325Thu, 27 Sep 2012 07:17:49 -0800AceRockMagic the Gathering is Turing complete
http://www.metafilter.com/119840/Magic%2Dthe%2DGathering%2Dis%2DTuring%2Dcomplete
The collectible card game <a href="http://en.wikipedia.org/wiki/Magic:_The_Gathering">Magic: The Gathering</a> is <a href="http://www.toothycat.net/~hologram/Turing/HowItWorks.html">Turing complete</a>. This means that one could, in theory, use a very particular arrangement of Magic: The Gathering cards to compute anything that any computer is capable of computing, albeit very slowly. This result seems to have been inspired by <a href="http://draw3cards.com/questions/2851/is-magic-turing-complete/3225#3225">this post at Draw 3 Cards</a>, a M:tG theory site (and <a href="http://cstheory.stackexchange.com/questions/2052/is-magic-the-gathering-turing-complete">cross-posted at StackExchange</a>).
A few other games are Turing complete, including Minecraft, via its redstone circuits (more or less, since the Minecraft engine can't handle a truly infinite amount of memory). <a href="http://en.wikipedia.org/wiki/List_of_NP-complete_problems#Games_and_puzzles">Quite a few other games</a>, including Tetris and Minesweeper, are <a href="http://en.wikipedia.org/wiki/NP-complete">NP-Complete</a>, which is similar sounding but unrelated.
(<a href="http://games.slashdot.org/story/12/09/12/0059200/magic-the-gathering-is-turing-complete">via Slashdot</a>) tag:metafilter.com,2012:site.119840Tue, 11 Sep 2012 18:25:30 -0800jedicusGnitros Tuo Gnitros
http://www.metafilter.com/118356/Gnitros%2DTuo%2DGnitros
<a href="http://youtu.be/SJwEwA5gOkM">Sorting Out Sorting</a> An exploration of sorting techniques by <a href="http://en.wikipedia.org/wiki/Ronald_Baecker">Professor Ronald Baecker</a>. tag:metafilter.com,2012:site.118356Sat, 28 Jul 2012 06:17:04 -0800Ad hominemHURF DURF YOUTUBE COMMENTATOR
http://www.metafilter.com/117917/HURF%2DDURF%2DYOUTUBE%2DCOMMENTATOR
<a href="http://www.jwz.org/blog/2012/07/herp-derp-youtube-comments/">Turn all Youtube Comments into "HERP DERP" - for Firefox, Safari, Opera and Chrome.</a> tag:metafilter.com,2012:site.117917Sun, 15 Jul 2012 17:34:18 -0800The WhelkTiny Transactions on Computer Science
http://www.metafilter.com/114728/Tiny%2DTransactions%2Don%2DComputer%2DScience
<a href="http://tinytocs.org/">Tiny Transactions on Computer Science</a> <em>...the premier venue for computer science research of 140 characters or less.</em> tag:metafilter.com,2012:site.114728Tue, 10 Apr 2012 08:28:56 -0800DeathaliciousClassic Nintendo Games are (NP-)Hard
http://www.metafilter.com/113812/Classic%2DNintendo%2DGames%2Dare%2DNPHard
<a href="http://arxiv.org/pdf/1203.1895v1.pdf">Some (slightly generalized) classic Nintendo games are NP-Hard. [pdf]</a> From the paper:
<blockquote>We prove NP-hardness results for five of Nintendo's largest video game franchises: Mario, Donkey Kong, Legend of Zelda, Metroid, and Pokemon. Our results apply to Super Mario Bros. 1, 3, Lost Levels, and Super Mario World; Donkey Kong Country 1-3; all Legend of Zelda games except Zelda II: The Adventure of Link; all Metroid games; and all Pokemon role-playing games. For Mario and Donkey Kong, we show NP-completeness. In addition, we observe that several games in the Zelda series are PSPACE-complete...</blockquote>
<blockquote>For these games, we consider the decision problem of reachability: given a stage or dungeon, is it possible to reach the goal point t from the start point s? If it is hard to decide even this question, then it is certainly hard to find an optimal path. Our results apply to generalizations of the games where we only generalize the map size and leave all other mechanics of the games as they are in their original settings. All of our NP-hardness proofs are by reduction from 3-SAT, and the proofs for Mario, Donkey Kong, Legend of Zelda, and Metroid rely on a common construction, while the proof for Pokemon is based on a reduction to Push-1. We show that certain Zelda games are in fact PSPACE-complete, by reducing from PushPush-1.</blockquote>
Wikipedia on <a href="http://en.wikipedia.org/wiki/Np_hard">NP-Hard problems</a> and the <a href="http://en.wikipedia.org/wiki/3SAT#3-satisfiability">3-SAT problem</a>. tag:metafilter.com,2012:site.113812Tue, 13 Mar 2012 11:01:48 -0800albrechtAm I wasting my time organizing e-mail?
http://www.metafilter.com/111680/Am%2DI%2Dwasting%2Dmy%2Dtime%2Dorganizing%2Demail
<a href="http://people.ucsc.edu/~swhittak/papers/chi2011_refinding_email_camera_ready.pdf">Am I wasting my time organizing e-mail? A study of e-mail refinding.</a> (single link academic paper in .pdf.) tag:metafilter.com,2012:site.111680Mon, 16 Jan 2012 08:25:34 -0800escabecheBreaking the Coppersmith-Winograd barrier
http://www.metafilter.com/109901/Breaking%2Dthe%2DCoppersmithWinograd%2Dbarrier
<em>For twenty years, the fastest known algorithm to multiply two n-by-n matrices, due to Coppersmith and Winograd, took a leisurely O(n^2.376) steps. Last year, though, buried deep in his <a href="http://www.maths.ed.ac.uk/pg/thesis/stothers.pdf">PhD thesis</a>, Andy Stothers discussed an improvement to O(n^2.374) steps. And today, <a href="http://www.cs.berkeley.edu/~virgi/">Virginia Vassilevska Williams</a> of Berkeley and Stanford, released a <a href="http://www.cs.berkeley.edu/~virgi/matrixmult.pdf">breakthrough paper [pdf]</a> that improves the matrix-multiplication time to a lightning-fast O(n^2.37<strong>3</strong>) steps. [<a href="http://www.scottaaronson.com/blog/?p=839">via</a>]</em> First section of the Introduction copied from the paper:
<em>The product of two matrices is one of the most basic operations in mathematics and computer science. Many other essential matrix operations can be efficiently reduced to it, such as Gaussian elimination, LUP decomposition, the determinant or the inverse of a matrix [1]. Matrix multiplication is also used as a subroutine in many computational problems that, on the face of it, have nothing to do with matrices. As a small sample illustrating the variety of applications, there are faster algorithms relying on matrix multiplication for graph
transitive closure (see e.g. [1]), context free grammar parsing [19], and even learning juntas [12].
Until the late 1960s it was believed that computing the product C of two n x n matrices requires essentially a cubic number of operations, as the fastest algorithm known was the naive algorithm which indeed runs in O(n^3) time. In 1969, Strassen [18] excited the research community by giving the ﬁrst subcubic time algorithm for matrix multiplication, running in O(n^2.808) time. This amazing discovery spawned a long line of research which gradually reduced the matrix multiplication exponent omega over time. In 1978, Pan [13] showed omega < 2.796. The following year, Bini et al. [4] introduced the notion of border rank and obtained omega < 2.78. Schonhage [16] generalized this notion in 1981, proved his tau-theorem (also called the asymptotic sum inequality), and showed that omega < 2.548. In the same paper, combining his work with ideas by Pan, he also showed omega < 2.522. The following year, Romani [14] found that omega < 2.517. The ﬁrst result to break 2.5 was by Coppersmith and Winograd [9] who obtained omega < 2.496. In 1986, Strassen introduced his laser method which allowed for an entirely new attack on the matrix multiplication problem. He also decreased the bound to omega < 2.479. Three years later, Coppersmith and Winograd [10] combined Strassen’s technique with a novel form of analysis based on large sets avoiding arithmetic progressions and obtained the famous bound of omega < 2.376 which has remained unchanged for more than twenty years.
In 2003, Cohn and Umans [8] introduced a new, group-theoretic framework for designing and analyzing matrix multiplication algorithms. In 2005, together with Kleinberg and Szegedy [7], they obtained several novel matrix multiplication algorithms using the new framework, however they were not able to beat 2.376.
Many researchers believe that the true value of omega is 2. In fact, both Coppersmith and Winograd [10] and Cohn et al. [7] presented conjectures which if true would imply omega = 2. Recently, Alon, Shpilka and Umans [2] showed that both the Coppersmith-Winograd conjecture and one of the Cohn et al. [7] conjectures contradict a variant of the widely believed sunﬂower conjecture of Erdos and Rado [11]. Nevertheless, it could be that at least the remaining Cohn et al. conjecture could lead to a proof that omega = 2.</em> tag:metafilter.com,2011:site.109901Tue, 29 Nov 2011 13:48:43 -0800albrechtEleven Equations True Computer Science Geeks Should (at Least Pretend to) Know
http://www.metafilter.com/109888/Eleven%2DEquations%2DTrue%2DComputer%2DScience%2DGeeks%2DShould%2Dat%2DLeast%2DPretend%2Dto%2DKnow
<a href="http://www.elegantcoding.com/2011/11/eleven-equations-true-computer-science.html">Eleven Equations True Computer Science Geeks Should (at Least Pretend to) Know</a> The author doesn't go into much detail on what these equations mean, so here's additional background:
<ol>
<li>Binomial Co-efficient: <a href="http://mathworld.wolfram.com/BinomialCoefficient.html">explanation</a>, <a href="http://rosettacode.org/wiki/Evaluate_binomial_coefficients">source code</a></li>
<li><a href="http://tomtech999.wordpress.com/2007/12/27/de-morgans-law/">De Morgan's Law</a></li>
<li>Eigenvectors: <a href="http://www.youtube.com/watch?v=lXNXrLcoerU">lecture (long, but helpful)</a>, <a href="http://spikedmath.com/242.html">unfunny cartoon</a>, <a href="http://www.miislita.com/information-retrieval-tutorial/matrix-tutorial-3-eigenvalues-eigenvectors.html">tutorial</a> <small>Disclosure: I still have no clue what eigenvectors are or why they're useful</small></li>
<li>Pumping Lemma - <a href="http://stackoverflow.com/questions/461619/in-laymens-terms-what-is-the-pumping-lemma">in layman's terms</a></li>
<li>Information entropy - measures how little (or how much) information there is in an event. Different possible outcomes (say, a coin flip) translate into entropy. The theory can be used, for example, to <a href="http://crypto.stackexchange.com/questions/374/how-should-i-calculate-the-entropy-of-a-password">measure the strength of a password</a> -- the more entropy, the harder it is to crack.</li>
<li>Bayes Theorem - maybe best known for its <a href="http://en.wikipedia.org/wiki/Bayesian_spam_filtering">use in identifying spam</a>.</li>
<li>Fermat's Little Theorem - basically, if <em>p</em> is a prime number, then <em>(a<sup>p</sup> - a)</em> will be evenly divisible by <em>p</em>. It's a way of identifying <a href="http://en.wikipedia.org/wiki/Fermat_primality_test">whether a given number is probably prime</a>. <a href="http://bhavya-dabas.suite101.com/fermats-little-theorem-and-rsa-cryptography-a171697">Very useful in cryptography</a>.</li>
<li>Natural Join - used extensively in relational databases (although more often manifested in the somewhat-related <a href="http://www.tomjewett.com/dbdesign/dbdesign.php?page=jointypes.php"><code>INNER JOIN</code></a>)</li>
<li>Fixed-Point - another concept I don't fully get, heavily involved in <a href="http://python.about.com/od/gettingstarted/qt/beg_lamda.htm">lambda calculus</a>. <a href="http://playingwithpointers.com/archives/590">Here's an explanation focusing on Haskell</a></li>
<li>O(n) - pretty fundamental concept in programming algorithms - <a href="http://rob-bell.net/2009/06/a-beginners-guide-to-big-o-notation/">how much time will this algorithm take to run with n inputs</a>. Best possible case is O(1) (hash-lookups are often close to O(1)). Worst possible case is O(n!) (O(n*(n-1)*(n-2)…*2*1), brute-force solution to the <a href="http://en.wikipedia.org/wiki/Travelling_salesman_problem">travelling salesman problem</a>).</li>
<li>Euler's identity - actually, he just includes it because it's pretty. It's been called the most beautiful theorem in mathematics (<a href="http://www.metafilter.com/89918/Math-is-beautiful">previously</a>).</li>
</ol> tag:metafilter.com,2011:site.109888Tue, 29 Nov 2011 08:40:27 -0800DeathaliciousStanford online courses
http://www.metafilter.com/109683/Stanford%2Donline%2Dcourses
Stanford has announced new online courses for January 2012. Like the three courses currently running (<a href="https://www.ai-class.com/">1</a>,<a href="http://www.ml-class.org/">2</a>,<a href="http://www.db-class.org/">3</a>), these courses are free, open to the general public, and have no required textbook (<a href="http://www.metafilter.com/106264/CS221">previously</a>). <a href="http://www.cs101-class.org">CS 101</a>
<a href="http://www.algo-class.org">Design & Analysis of Algorithms I</a>
<a href="http://www.game-theory-class.org">Game Theory</a>
<a href="http://www.saas-class.org">Software Engineering for Software as a Service</a>
<a href="http://www.hci-class.org">Human-Computer Interaction</a>
<a href="http://www.crypto-class.org">Cryptography</a>
<a href="http://www.pgm-class.org">Probabilistic Graphical Models</a>
<a href="http://jan2012.ml-class.org">Machine Learning</a> (same course as currently running)
<a href="http://www.nlp-class.org">Natural Language Processing</a>
<a href="http://www.launchpad-class.org">The Lean Launchpad</a>
<a href="http://www.venture-class.org">Technology Entrepreneurship</a> tag:metafilter.com,2011:site.109683Tue, 22 Nov 2011 07:54:54 -0800-jf-CS221
http://www.metafilter.com/106264/CS221
Stanford's 'Introduction to Artificial Intelligence' <a href="http://www.ai-class.com/">course</a> will be <a href="http://spectrum.ieee.org/automaton/robotics/artificial-intelligence/you-you-can-take-stanfords-intro-to-ai-course-next-quarter-for-free">offered</a> free to anyone online this fall. The course will be taught by <a href="http://robots.stanford.edu/">Sebastian</a> <a href="http://en.wikipedia.org/wiki/Sebastian_Thrun">Thrun</a> (Stanford) and <a href="http://norvig.com/">Peter</a> <a href="http://en.wikipedia.org/wiki/Peter_Norvig">Norvig</a> (Google, Director of Research), who expect to deal with the historically large course size <a href="http://developers.slashdot.org/story/11/08/04/1646210/Stanford-Intro-To-AI-Course-Offered-Free-Online">using</a> tools like Google <a href="http://www.google.com/moderator/">Moderator</a>. There will two 75 min lectures per week, weekly graded homework assignments and quizzes, and the course is expected to require roughly 10 hours per week. Over 10,000 students have already signed up.
<small>Btw, Sebastian Thrun & Google's driverless car recently <a href="http://tech.slashdot.org/story/11/08/05/2250249/Googles-Self-Driving-Car-Crashes">crashed</a></small> tag:metafilter.com,2011:site.106264Sat, 06 Aug 2011 10:41:38 -0800jeffburdgesRegular Expressions Can Be Simple and Fast
http://www.metafilter.com/90170/Regular%2DExpressions%2DCan%2DBe%2DSimple%2Dand%2DFast
Russel Cox, one of the people behind Google's new programming language Go, has written a three part series on regular expressions. It's a nice mix of computer science theory, programming, and history: <a href="http://swtch.com/~rsc/regexp/regexp1.html" title="but is slow in Java, Perl, PHP, Python, Ruby, ...">Regular Expression Matching Can Be Simple And Fast</a>, <a href="http://swtch.com/~rsc/regexp/regexp2.html">Regular Expression Matching: the Virtual Machine Approach</a>, and <a href="http://swtch.com/~rsc/regexp/regexp3.html">Regular Expression Matching in the Wild</a>. tag:metafilter.com,2010:site.90170Wed, 17 Mar 2010 05:55:17 -0800chunking expressHow To Program
http://www.metafilter.com/86107/How%2DTo%2DProgram
<a href="http://www.reddit.com/r/carlhprogramming/?count=125&after=t3_9oizi">A free computer-programming course on reddit.</a> Click "prev" for more lessons. 113 lessons so far. tag:metafilter.com,2009:site.86107Sat, 24 Oct 2009 08:37:36 -0800grumblebeeI love the smell of alkali metals in the morning...
http://www.metafilter.com/51940/I%2Dlove%2Dthe%2Dsmell%2Dof%2Dalkali%2Dmetals%2Din%2Dthe%2Dmorning
<a href="http://video.google.com/videoplay?docid=-2134266654801392897&q=alkali">The dog's nuts of the periodic table.</a> tag:metafilter.com,2006:site.51940Tue, 30 May 2006 08:22:41 -0800ozomatliYo, books!
http://www.metafilter.com/40819/Yo%2Dbooks
<a href="http://www.bhargav.com/books/index.html">Yo, books!</a> Absolute masses of maths, physics, and CS books <i>chez</i> bhargav. Via <a href="http://www.madamemartin.com">Madame Martin</a> tag:metafilter.com,2005:site.40819Tue, 29 Mar 2005 20:37:00 -0800Wolof