The latest blog posts to take off on Hacker News. 2,851 posts.
A little while back I found need of a PNG loader for a small project of mine . Being a complete tool I of course decided to write my own -- after all, why save yourself effort when there are still wheels waiting to be reinvented? You can check the source to the inflater code here if you so like - it's quite cleanly…
Flattening images of curled pages, as an optimization problem.
Around 2006, my friend Dan Christensen created a fascinating picture of all the roots of all polynomials of degree ≤ 5 with integer coefficients ranging from -4 to 4:
Petr Švenda, Matúš Nemec, Peter Sekan, Rudolf Kvašňovský, David Formánek, David Komárek, and Vashek Matyáš, Masaryk University
An image kernel is a small matrix used to apply effects like the ones you might find in Photoshop or Gimp, such as blurring, sharpening, outlining or embossing. They're also used in machine learning for 'feature extraction', a technique for determining the most important portions of an image. In this context the…
My new office space suffers from a shortage of photons, so I’ve been wiring up light fixtures. As I was snaking 14-gauge cable through the ceiling cavity, I began to wonder: Why is it called 14-gauge? I know that the gauge specifies the size of the copper conductors, but how exactly? The number can’t be a simple…
Gradient descent is a standard tool for optimizing complex functions iteratively within a computer program. Its goal is: given some arbitrary function, find a minumum. For some small subset of functions - those that are convex - there's just a single minumum which also happens to be global. For most realistic…
Update! I tested more hash functions in a follow-up post. See More Hash Function Tests .
I recently read “Adventure Time: Volume 1”, a comic book based on the smart animated series of the same name. In the comic, I found some odd looking messages at the …
The most common question students have about mathematics is “when will I ever use this?” Many math teachers would probably struggle to give…
We can define roundness in many ways. For example, as you may know, the circle is the shape that given a fixed perimeter maximizes the area. This definition has many problems. One of the problems is that countries generally have chaotic perimeters (also known as borders), so they tend to be much longer than they seem…
Understanding gradient boosting with interactive 3d-demonstrations
Generalized linear models (GLMs) are indispensable tools in the data science toolbox. They are applicable to many real-world problems involving continuous, yes/no, count and survival data (and more). The models themselves are intuitive and can be used for inference and prediction. A few very high quality free and open…
If you would follow the road to linear algebra here are some trustworthy signposts.
The other day I was amused to find a quote from Einstein , in 1936, about how hard it would be to quantize gravity: “like an attempt to breathe in empty space.” Eight decades later, I think we can still agree that it’s hard.
Posted by Joshua Bloch, Software EngineerI remember vividly Jon Bentley's first Algorithms lecture at CMU, where he asked all of us incoming Ph.D. ...
Engineering at Forward | UCLA CS '19
What is the most rectangular country?
Posted by Matt Braithwaite, Software Engineer Quantum computers are a fundamentally different sort of computer that take advantage of aspec...
When the central heating takes effect I'll get up and make myself some tea and porridge to which I'll add some nuts and fruit. I'll switch on The World Service to hear the news, and then make a few phone calls about damp-proofing. And I'll probably plant the daffodil bulbs for Spring (it says on the packet they should…
I write about Startups, coding and Physics
I've been reading a lot of Lisp books lately, some more advanced than others. All of the introductory books I've seen cover the idea of symbolic computation, but most of them breeze past it with just a few pages about "symbols" and "quoting". For many programmers coming from non-Lisp languages these are new, foreign…
The Rule of 72 is a great mental math shortcut to estimate the effect of any growth rate, from quick financial calculations to population estimates. Here’s…
The fundamental theorem of arithmetic states that every positive integer can be factorized in one way as a product of prime numbers. This statement has to be appropriately interpreted: we count the…
Posts and writings by Datanice
Some time ago I gave a talk in which I showed that something unexpected happened with a deck of playing cards. I had some volunteers try it, and while they did so I talked about just how many orderings there are for 52 cards. I computed (an approximation to) $52!$ (52 factorial) by hand. It's not so hard - you just…
