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Fast Lossless Color Image Compression
In the research field of compression, the usual goal is to achieve the best possible compression rate. The best known algorithms, however, are very slow, and sometimes impractical for real-world ap…
New
The latest blog posts to take off on Hacker News. 2,851 posts.
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Fields medalist Tim Gowers: Elsevier — my part in its downfall
The Dutch publisher Elsevier publishes many of the world’s best known mathematics journals, including Advances in Mathematics, Comptes Rendus, Discrete Mathematics, The European Journal of Co…
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Damn Cool Algorithms: Quadtrees and Hilbert Curves
Last Thursday night at Oredev, after the sessions, was "Birds of a Feather" - a sort of mini-unconference. Anyone could write up a topic on the whiteboard; interested individuals added their names, and each group got allocated a room to chat about the topic. I joined the "Spatial Indexing" group, and we spent a…
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The faster-than-fast Fourier transform
For a large range of practically useful cases, MIT researchers find a way to increase the speed of one of the most important algorithms in the information sciences.
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Damn Cool Algorithms: Fountain Codes
Posted by Nick Johnson | Filed under bittorrent , lt-codes , damn-cool-algorithms , fountain-codes
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Darts, Dice, and Coins: A beautiful article on a beautiful algorithm
Earlier this year, I asked a question on Stack Overflow about a data structure for loaded dice . Specifically, I was interested in answering this question:
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A Perl Regular Expression That Matches Prime Numbers
Take a look at this Perl regular expression: perl -lne '(1x$_) =~ /^(11+?)\1+$/ && print "$_ is composite"' This regular expression matches only the composite numbers (and doesn't match prime numbers). Can you figure out how it works? I'll give the explanation below but try to figure it…
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VP trees: A data structure for finding stuff fast
<img src="http://stevehanov.ca/wavelet/cup.png"/> Let's say you have millions of pictures of faces tagged with names. Given a new photo, how do you find the name of person that the photo most resembles? <p> In the cases I mentioned, each record has hundreds or thousands of elements: the pixels in a photo, or patterns…
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A primer on Bezier curves
A detailed explanation of Bézier curves, and how to do the many things that we commonly want to do with them.
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Fuzzy string search
Intro Fuzzy search algorithms (also known as similarity search algorithms) are a basis of spell-checkers and full-fledged search engines lik...
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Matrix multiplication in O(n^2.373)
For twenty years, the fastest known algorithm to multiply two n-by-n matrices, due to Coppersmith and Winograd, took a leisurely O(n2.376) steps. Last year, though, in his PhD thesis, Andrew Stot…
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Equations True Computer Science Geeks Should (at Least Pretend to) Know
This idea is a complete rip off an article that appeared in Wired a little while ago and it got me thinking what would my list for Compu...
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Abstract algebra for developers and people who hate math
Hi. I think math is really cool, but, most people (sadly) don't think so. This includes many programmers who in fact enjoy many of the sam...
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A shuffled deck of cards is unique in all human history
Every time you shuffle a deck of playing cards, it's probably a unique order, never before seen in human history.
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The (logarithmic) calendar I want
I was looking at my Google Calendar tonight and I realized that this software was encouraging a way of thinking about time which has signifi...
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Recursive Functions of Symbolic Expressions and Their Computation by Machine
This paper appeared in Communications of the ACM in April 1960. It is the original paper on Lisp.
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How to turn a biased coin into a Fair Coin
Fair Coins are the currency of Userland. A Fair Coin flips fifty-fifty with mathematical exactness. In the real world most coins are pretty fair, but you never know whether there might be a small bias to one side or another. This presents Lauren Ipsum , a girl who's lost in Userland, with a problem. No one wants her…
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Fibonacci Flim-Flam.
physics, history of science, pseudoscience, hoaxes, writing, education, skepticisism, humor, quotes, illusions, 3d stereo photography.
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Quake's Fast Inverse Square Root
I'm no graphics expert, but appreciate why square roots are useful. The Pythagorean theorem computes distance between points, and dividing by distance helps…
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Algorithmic symphonies from one line of code
Lately, there has been a lot of experimentation with very short programs that synthesize something that sounds like music. I now want to sha...
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Finding Love Optimally
Like many in operations research, my research interests often creep over into my everyday life. Since I work on scheduling issues, I get particularly concerned with everyday scheduling, to the consternation of my friends and family (“We should have left six minutes ago: transportation is now on the critical path!”)…