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Math & Algorithms

The most popular blog posts about math & algorithms on Hacker News. 179 posts.

2018
33

For mathematicians, = does not mean equality

Every now and then I hear some ridiculous things about the equals symbol. Some large subset of programmers—perhaps related to functional programmers, perhaps not—seem to think that = should only and ever mean “equality in the mathematical sense.” The argument usually goes, Functional programming gives us back that…

39

Statistics, Fast and Slow

Written for and first published in the Financial Times on 13 April 2018. One way to understand China is to look at the statistics. Real income per person has increased nearly tenfold since 1990. Si…

46

Lost in Math

Sabine Hossenfelder’s new book Lost in Math should be starting to appear in bookstores around now. It’s very good and you should get a copy. I hope that the book will receive a lot of a…

48

Proof-Of-Work is a Decentralized Clock

This is an explanation of the key function on Proof-of-Work in the Bitcoin blockchain. It focuses on the one feature of Proof-of-Work that is essential and shows that other features often talked about such as security are secondary side-effects, useful, but not essential. This explanation rests on illustrating a few…

52

Probabilistic Filters By Example

Probablistic filters are high-speed, space-efficient data structures that support set-membership tests with a one-sided error. These filters can claim that a given entry is definitely not represented in a set of entries, or might be represented in the set. That is, negative responses are conclusive, whereas positive…

55

A study of musical scales (2017)

PREFACE. This essay was written in 2009. Since then, a few errata have been corrected and I embedded the youtube videos, but there have been no substantial additions. I think it still holds up fairly well, but if I were to rewrite it today, I would change some things. My main regret is using the criteria of maximum…

57

Deciphering the postcard-sized raytracer

"He's done it again!" was my first thought as I looked at the back of a postcard sized Pixar flier [1] which was covered in code. In the lower right corner, the blob of statements and expressions had been signed by none other than Andrew Kensler. For those who are not familiar with him, Andrew is the programmer who…

58

Secrets of smooth Béziers

I haven’t posted here much lately, and I admit, it’s because I’ve gotten sidetracked thinking about curves again. I did my PhD thesis on curves, so spent years thinking about them, then put that on hold for a while, aside from some work in crunching font file sizes down.