### Stack Overflow

I answer algorithm questions on Stack Overflow. Here is my profile.

### Strawberry Fields

Strawberry Fields is a combinatorial optimization problem posed by ITA Software. I started working on it because I thought it was neat that, for the natural LP relaxation, the column generation subproblem is the two-dimensional maximum subarray problem examined by Jon Bentley in *Programming Pearls*. It turns out that Kadane’s algorithm for the maximum subarray problem cannot handle the side constraints introduced by branch and price, but the solver that I built for Strawberry Fields is still four orders of magnitude faster on the sample instances than a commercial integer program solver with no problem-specific tuning.

Since ITA Software has stopped using Strawberry Fields as a recruiting puzzle, here is my source code (tbz), to which I reserve all rights.

### PlanetLab

When I was a PhD student at Princeton, I worked on PlanetLab, a globally distributed cloud computing service for networking research. I implemented from scratch version 4 of Node Manager, which runs on each server and handles requests to provision virtual machines, and I maintained the backend of Sirius, a service that accepts reservations for system resources. I also wrote tutorial documentation for both Sirius and the programmatic interface to PlanetLab Central, the default service for managing collections of virtual machines.

### Dodge

Dodge is a simple Flash game by Lewpen Kinross-Skeels. It’s difficult to play on a touchpad, and that was my excuse for not beating my friends’ scores until I wrote a program to do this (Vimeo).

### Facebook puzzles

Facebook used to maintain a small collection of programming puzzles. I wrote an unofficial guide that was linked to by Slashdot.

### Project Euler

Project Euler is a growing collection of mathematics/programming problems. I solved the first 250 and briefly was ranked #1.

### Operating Systems

I wrote specifications for projects two and three of Princeton’s COS 318 (Operating Systems).

### Snake lemma

The snake lemma is a basic result in a branch of mathematics called homological algebra. I wrote a program to find a proof by diagram chasing.

### Graph polynomials

For my research, I wrote Java applets that, given a rooted graph where edges (Java) or vertices (Java) are deleted independently with probability 1 - *p*, compute the expected number of non-root vertices in the connected component containing the root.

### “Dahlia”

“Dahlia”, my entry in Keith Enevoldsen’s Logo 15-Word Challenge, is my oldest surviving program. It won the “Pure Logo” prize.