Archive for category: Math

The Marriage (or Secretary) Problem

May 16, 2014 | Math | By: Mark VandeWettering

Over on Facebook, fellow Pixarian Arun pointed out this story on a problem I encountered in my undergraduate schooling as “The Marriage Problem”, which I also heard of as “The Secretary Problem”. The idea is that you are supposed to find a wife (or secretary) out of a list of $n$ possibles. Each one is […]

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Products of Primes and the Primorial Function…

February 26, 2014 | Math | By: Mark VandeWettering

A friend of mine was working on a programming exercise, and it turns it out was based on a chunk of math which I thought I should have seen before, but either have not seen or have forgotten. It’s basically that the products of all primes less than some number n is less than or […]

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January 4, 2014 | Games and Diversions, Math | By: Mark VandeWettering

This is a math/geeky/computer post of something relatively simple, but it arose in the wild in a program that I wrote several years ago, and when I saw it again, it confused me, and I spent a bit of time thinking about it, and I thought I might just write it up. If math/geeky/computer stuff […]

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Factoring numbers from Ivar Peterson’s The Mathematical Tourist

August 18, 2013 | Math | By: Mark VandeWettering

I’m a bit of a math geek. I have been periodically fascinated by the factoring of large numbers, which plays such an important role in modern cryptography algorithms like RSA. I’ve coded a few of the non-trivial factorization algorithms, such as Pollard-rho, but haven’t done a whole lot with it. It mostly remains just a […]

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On Theo Jansen’s walking mechanism…

May 23, 2013 | 3D printing, Math, Toys and Gadgets | By: Mark VandeWettering

If you haven’t heard of Theo Jansen and his incredible walking machines, I can’t do them justice with words. Check this out: His work is accessible from I find his creations amazingly cool. And others do as well, even hamsters (although cats seem less impressed): But while I’ve found these things fascinating, I didn’t […]

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Russ Cox muses about Fields and Reed-Solomon codes

April 10, 2012 | Computer Science, Math | By: Mark VandeWettering

I’ve been pretty interested in codes of all sort, both the cryptographic codes and the codes that are used to provide error detection and correction. While I’ve played around quite a bit with convolutional codes, I haven’t really every bothered to develop more than a cursory understanding of the Reed-Solomon error correcting codes which have […]

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Happy π-day!

March 14, 2012 | Math | By: Mark VandeWettering

Today is π-day (3/14) as well as Albert Einstein’s birthday. I was trying to get inspired to produce something pi related, so I scanned my bookshelves for the kind of fun recreational mathematics books that provide the raw grist for my geek mill. I found a copy of Peter Beckmann’s A History of Pi, which […]

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A nifty partition of 1..16

November 15, 2011 | Math, Puzzles | By: Mark VandeWettering

Courtesy of Phil Harvey’s Puzzle « Programming Praxis, I discovered that the numbers from 1..16 can be partitioned into two 8 element sets, with these nifty identities! 2+3+5+8+9+12+14+15 == 1+4+6+7+10+11+13+16 22+32+52+82+92+122+142+152 == 12+42+62+72+102+112+132+162 23+33+53+83+93+123+143+153 == 13+43+63+73+103+113+133+163 There has to be a good way to use this to make a cool geometric puzzle as well.\ Bonus: […]

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Baseball and Pascal’s Triangle

October 28, 2011 | Baseball, Math | By: Mark VandeWettering

I was standing in Tom’s office, and asked him a simple probability question (and a timely one, given the World Series): If the odds of a particular team winning against their opponent is some probability p, what are the odds that they will win a 7 game series? If you had any probability at all, […]

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Nifty paper on Batting Average…

October 27, 2011 | Baseball, Math | By: Mark VandeWettering

For some reason, I never do much reading about baseball during the season itself. But as the World Series approaches its end (still hoping for a game seven) I have started to dust off some of my reading materials. A couple years ago, I mentioned this work by Lawrence Brown on this blog, but the […]

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Difficulties with the Hilbert Transform…

September 28, 2011 | Amateur Radio, Math, My Projects | By: Mark VandeWettering

Well, it wasn’t so much a difficulty with the Hilbert transform as a difficulty with my understanding. But with the help of my good friend Tom, my understanding was soon put right, and I thought it might make an interesting (in other words, horribly boring to anyone but myself) post, and at the very least, […]

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How is PWM modulation like AM modulation?

April 1, 2011 | Amateur Radio, electronics, Math | By: Mark VandeWettering

In thinking about the 555 timer AM transmitter that I constructed last night and trying to understand how it might work, I eventually ended up with a basic question about PWM modulation. It boiled down to this: if you are generating a pulse width modulation signal with a rate of (say 540khz) but pulses whose […]

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The HOPALONG Orbit Fractal

March 24, 2011 | Math, My Projects | By: Mark VandeWettering

While watching TV, I coded up a custom renderer for the HOPALONG orbit fractal, generated 300 frames, and encoded it with FFMPEG. Without further ado:

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HOPALONG, from Dewdney’s Armchair Universe

March 24, 2011 | Arts and Crafts, Math | By: Mark VandeWettering

All this fiddling around with the Lorenz attractor has made me try to think of other simple, easy graphics hacks that I could make. I recalled that A.K. Dewdney had some simple graphics hacks in one of his Computer Recreations column back in the 1980s. It turns out that Wallpaper for the mind was published […]

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The Chaotic Lorenz Water Wheel

March 22, 2011 | Amateur Science, Math | By: Mark VandeWettering

Doing a bit more reading, I found out that the equations that make up the Lorenz attractor (which are derived from a simplified model of 2D fluid flow with a superimposed temperature gradient) can also be thought of as governing another physical system. Imagine a water wheel, with a number of buckets spaced evenly around […]

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