## Tinkerbell Map

The Tinkerbell map is a chaotic dynamical system with an interesting strange attractor. The iterated function is

$$x_{n+1} = x_n^2 - y_n^2 + a x_n + b y_n$$

$$y_{n+1} = 2 x_n y_n + c x_n + d x_n$$

In this example, the parameters are $a=0.9$, $b=-0.6013$, and $c=2.0$. $d$ is randomly chosen on $(0.35, 0.55)$, and the colour is based on $d$.

## Setting up a new mac - notes

My notes on setting up a new mac, probably only useful for me.

## Git: Move commits to new branch

Suppose you have a few commits in a git repository, and some of them are on the wrong branch. They're listed below from the oldest (a) to newest (g). The letters represent the commit checksums.

a b c d e f g

You want to move the bold commits b, d, and e to a new branch. So start by checking out the commit before the first bad one and creating a branch there.

## For future reference

Never underestimate the bandwidth of a station wagon full of tapes hurtling down the highway. Computer Networks, 3rd ed., p. 83. (paraphrasing Dr. Warren Jackson, Director, University of Toronto Computing Services (UTCS) circa 1985)

## SQLite Database is Locked

Spent a couple of days tracking down a strange error using PHPunit and SQLite for testing a complex application. The test suite kept throwing
PDOException: SQLSTATE[HY000]: General error: 5 database is locked
and halting in test that didn't touch the database. The problem was in an unrelated test that ran before it. The test uses iterators to examine database contents, but didn't iterate all the way through the result set. The iterator left the database locked.