Bob Jenkins' Web Site

New: 4TB disk drives have 4 platters, with a arm reading each side, that's 8 arms. They're all one one spindle, they move in sync. But the data rate is no better than one arm reading one platter. Why? They only have chips to control one head at a time, so they toggle which one head is active. If they had all heads read and write in parallel, striping data across all platters, a 4TB disk drive would read and write with a scan rate of 1.2GB/sec. Putting n heads at the tip of each arm would also increase scan rates by a factor of n. So, why doesn't any disk drive manufacturer do that? Beats me.

perpetual motion

Table of Contents (internal links):

Hashing
Here's a hash table, code for perfect hashing, a good hash function for hash table lookup, a FAQ, some theory, and code to search for new hash functions. I tried designing block ciphers and finding characteristics. I had an article published in Dr. Dobb's in September 1997.
Randomness
Have the cryptographic pseudorandom number generator ISAAC, a small noncryptographic pseudorandom number generator, a prize for breaking ISAAC, and ISAAC's background and theory. Also take some tests for randomness, and a table of orders of magnitude. Here are also some protocols and a unit vector generator.
Collections
See some skits from Boy Scouts, SQL tricks from Oracle, near-future speculations, some paper airplanes, some recipies, and some cartoons that I wrote in college.
Math
Look into pentagonal tiles, formulae for n-body orbit simulations, code for the HOMFLY knot polynomial, voting methods, choosing random passwords, jenny for pairwise testing, some error correction codes, a an april fool's design spec, and a web page for choosing colors.
Physics
Consider perpetual motion machines, a dirigiped design, a scale model of the solar system, a page on exploring orbits with Java, Klemperer Rosettes, a simulation of Cruithne (a near-earth object), of figure-eight orbits, of binary star planetary orbits, a set of noncolliding orbits, some Dyson Swarms (pretty pictures!), some methods for the n-body problem, a description of the orbit applet used, and a tentative itzu world.
Home projects
See my half bath, a house design that will never be built, a dollhouse that did get built, some genealogical notes, and a roof rack for Justine's car.
Other
Here is my autobiography, a resume, a cong from the British Museum, a comparison of JPEG and JPEG 2000, a bit on software patents, my mom's art, and some early Bob photos. My wife Justine has a website too. Here are people I've encountered more than once.

Here are some other sites:

Send mail to Bob at bob_jenkins@burtleburtle.net.