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How Not To Sort By Average Rating
Users are rating items on your website. How do you know what the highest-rated items are?
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Conway's Game of Life, using floating point values instead of integers
A continuous version of Conway's Life, using floating point values instead of integers: supports many interesting phenomena such as gliders that can travel in any direction, rotating pairs of gliders, wickstretchers and the appearance of elastic tension in the 'cords' that join the blobs. Slides showing how the rule…
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Mihai Pătraşcu 1982–2012
A pathbreaking researcher taken too soon from us (src) Mihai Pătraşcu passed away on Tuesday of brain cancer, having not yet reached age 30. We, Dick and Ken, did not know about his year-…
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What does randomness look like?
On 13 June 1944, a week after the allied invasion of Normandy, a loud buzzing sound rattled through the skies of battle-worn London. The source of the sound was a newly developed German instrument …
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My IQ
Mathematics, applications of mathematics to life in general, and my life as a mathematician.
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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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The game of life emulated in the game of life
Conway's Game of Life, emulated in Conway's Game of Life: The life simulator used is Golly which has a built-in script to generate these metapixel grids (select a pattern, and choose "metafier.py" from the scripts list). Outer Totalistic Cellular Automata Meta-Pixel: The metacell uses a period 184 tractor beam, which…
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The Mathematical Hacker
The programming profession is blessed with a number of gifted essayists. Today I will pick on three of my favorites — Eric Raymond, Paul Graham, and Steve Yegge — because they all seem to disagree about why (and whether) mathematics is relevant to the practicing programmer. Their attitudes might be summarized as:
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How you eat corn on the cob predicts whether you're an analyst or algebraist
I like learning about odd connections between disparate things. This probably is the oddest example that I know. Broadly speaking, mathemat...
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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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Mastering Linear Algebra in 10 Days: Astounding Experiments in Ultra-Learning
The MIT Challenge My friend Scott Young recently finished an astounding feat: he completed all 33 courses in MIT’s fabled computer science curriculum, from Linear ... Read more
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Analysis of bank PIN numbers
Is your PIN number too predictable? Detailed analysis on PIN number databases.
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Damn Cool Algorithms: Homomorphic Hashing
Posted by Nick Johnson | Filed under homomorphic-hashing , damn-cool-algorithms , fountain-codes
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Damn Cool Algorithms: Cardinality Estimation
Posted by Nick Johnson | Filed under python , cardinality-estimation , damn-cool-algorithms
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Ice
Water is complicated and fascinating stuff! There are at least sixteen known crystal phases of ice, many shown in this diagram based on the work of Martin Chaplin: (Click for a larger version.) For…
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My Prime Factorization Sweater
I wore my Prime Factorization Sweater to KidlitCon09 , and it shows up in all my pictures, so I think it’s time for me to explain it.
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The software development final exam: Algorithms and Data Structures
If you would like me to grade your answers, please send an email to cperciva-exam-part1@tarsnap.com [EDIT: I have now finished marking part 1 answers; please do not send me any more] with your answers to the above questions along with the following two:
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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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The Two Egg Problem
Analysis of the classic "dropping two eggs from a building" interview question
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A Better Strategy for Hangman
Learn the optimal strategy for playing Hangman.
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Mona Lisa in 50 polygons, using a genetic algorithm (2008)
This weekend I decided to play around a bit with genetic programming and put evolution to the test, the test of fine art 🙂
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Why Multi-armed Bandit algorithms are superior to A/B testing (with Math)
In a recent post, a company selling A/B testing services made the claim that A/B testing is superior to bandit algorithms. They do make a compelling case that A/B testing is superior to one particular not very good bandit algorithm, because that particular algorithm does not take …
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A new kind of fractal?
Experimenting with the "divisibility" of complex numbers, I stumbled across this thingy. It looks like a fractal. Although the formula does not do any iterations. It reminds me of something. But I dont know what. Doing a Google image search brings up a couple of galaxies :) This image shows the region from (-1/-1) to…