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New
The latest blog posts to take off on Hacker News. 106 posts.
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When Greedy Algorithms Are Good Enough (2014)
Greedy algorithms are among the simplest and most intuitive algorithms known to humans. Their name essentially gives their description: do the thing that looks best right now, and repeat until nothing looks good anymore or you’re forced to stop. Some of the best situations in computer science are also when greedy…
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Regression to the mean is the main reason ineffective treatments appear to work
Jump to follow-up “Statistical regression to the mean predicts that patients selected for abnormalcy will, on the average, tend to improve. We argue that most improvements attributed to the p…
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Why I decided not to enter the $100k global warming time-series challenge
Interesting applied project for your students , or as a warning for decisions under uncertainty / statistical significance. Real money on the line so the length of time and number of entries required to get a winner may be an interesting dataset after this is all done.
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Google, D-Wave, and the case of the factor-10^8 speedup
Update (Dec. 16): If you’re still following this, please check out an important comment by Alex Selby, the discoverer of Selby’s algorithm, which I discussed in the post. Selby querie…
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Unexplored Areas in Data Compression
A good colleague of mine, Rich Geldreich put up a interesting article talking about his viewpoints in future directions in lossless…
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What Is Spacetime, Really?
On the 100th anniversary of Einstein’s Theory of Relativity, Stephen Wolfram discusses the nature of space and time, and fundamental theory of physics.
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Break a dozen secret keys, get a million more for free
[An in-depth blog post by Daniel J. Bernstein, crossposted between the ECRYPT blog and the cr.yp.to blog .]
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A Quasipolynomial Time Algorithm for Graph Isomorphism: The Details
Update 2017-01-09: Laci claims to have found a workaround to the previously posted error, and the claim is again quasipolynoimal time! Updated arXiv paper to follow. Update 2017-01-04: Laci has posted an update on his paper. The short version is that one small step of his analysis was not quite correct, and the result…
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Finite state machines as data structure for representing ordered sets and maps
It turns out that finite state machines are useful for things other than expressing computation. Finite state machines can also be used to compactly represent ordered sets or maps of strings that can be searched very quickly.
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Divisibility by 7 is a Walk on a Graph (2009)
Mathematics, applications of mathematics to life in general, and my life as a mathematician.
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The Mathematics of Paul Graham's Bias Test
A major problem in detecting biased decisionmaking is the problem of unknown inputs. For example, suppose a venture capitalist has a public portfolio which has funded 75% male founders and 25% female. Is this venture capitalist biased against women? It's impossible to know - perhaps only 10% of his applicants were …
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Quasi-Polynomial Algorithm for Graph Isomorphism
Update (Dec. 14): The long wait is over! Here’s Laci’s paper on the arXiv. So far, I’ve read it only deeply enough to note that it contains the following sentence: A group G ≤ S…
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Bayesian ranking of items with up and downvotes or 5 star ratings
Evan Miller wrote a great article How Not To Sort By Average Rating . He shows that simple formulas like score = upvotes - downvotes or score = upvotes / (upvotes + downvotes) don’t work. He proposes to use the lower bound of the Wilson score confidence interval. The formula is complicated and somewhat of a hack…
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A riddle wrapped in a curve
If you’re looking for a nice dose of crypto conspiracy theorizing and want to read a paper by some very knowledgeable cryptographers, I have just the paper for you. Titled “A Riddle Wrapped in an E…
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Magic: The Gathering Is Turing Complete (v5)
I'm assuming you're familiar with the basic idea of what a Turing machine is . There are a few parts to building one in Magic: a tape extending in two directions storing cells of a few different "colours"; a processing head that can read the current cell's colour, write a new colour and change its state if necessary…
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MathBox 2: PowerPoint Must Die
PowerPoint must die.
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Bell inequality violation finally done right
A few weeks ago, Hensen et al., of the Delft University of Technology and Barcelona, Spain, put out a paper reporting the first experiment that violates the Bell inequality in a way that closes off…
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Implementing Levenshtein Automata
Thanks to Ken Hironaka for kindly taking a lot of time to read and fix countless errors in this blog post!
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Introduction to Monte Carlo Tree Search
The subject of game AI generally begins with so-called perfect information games. These are turn-based games where the players have no information hidden from each other and there is no element of chance in the game mechanics (such as by rolling dice or drawing cards from a shuffled deck). Tic Tac Toe, Connect 4…
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The Math I Learned After I Thought Had Already Learned Math
True story: it’s possible to fly through your own secondary math education — honor roll bumper sticker on your mom’s minivan and all —Â but miss some of the Very Big Ideas of secondary …
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Discrete Analysis – A new type of math journal
This post is to announce the start of a new mathematics journal, to be called Discrete Analysis. While in most respects it will be just like any other journal, it will be unusual in one important w…
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Confirmed: The Last Great Prediction Of The Big Bang
A leftover glow unlike any other — of neutrinos — has finally been seen.
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Biggest image in the smallest space
What’s the biggest pixel size of a PNG image in the smallest number of bytes? I wanted to try to create an image that could be downloaded but whose pixel buffer would be too big to store in the RAM of a PC. Here is a PNG image of 6,132,534 bytes (5.8 MB) and 225,000 × 225,000 pixels (50.625 gigapixels), which, if…