Games

Sprouts, Dodgem, Dots-and-Boxes, Chomp, Sim (Ramsey Graph Coloring), Connect-6, Hex, Go 囲碁, Breakthrough

PVD-NYC

153 miles between the Providence and New York Amtrak stations, as the crow flies. At the Acela top speed (150 mph), it would be 1 hour. At top Shinkansen speeds, it would be 50 minutes. At top TGV speeds, it would be 45 minutes. However, currently, Acela takes 3 hours.

Laplacian

I wish there were a tool that would quickly solve Laplacians on a regular two-dimensional grid, for example in the NetPBM format.

Under what conditions can the Laplacian be solved "directly" using the Fourier transform, and under what must some sort of numerical method (e.g., multigrid) be used? Is is necessarily a computational "win" to use the Fourier tranform?

UPDATE: my solver using relaxation (or Successive Over-Relaxation)

Wikipedia

should be restricted only to primary sources.

Hash of words

Take a word, generate its primary Double Metaphone code (in uppercase). Take the MD5 hash of the code. Drop the least significant 8 bits, then take the 10 least significant bits remaining.

In reverse, here's a dictionary generated by this perl script run over Linux's /usr/share/dict/words. This script avoids one-syllable words, similar words, and words with short codes. With such a limited source word list, we must use bits 110-119 (0-indexed) to achieve full coverage of the all 10-bit-wide bitstrings. Other positions don't quite cover.

Sadly, speaking 100 words per minute works out to 16 bits per second, and even less if an error-correcting code is used.

Bus

From Harvard, you can take the 1 bus connecting to the 70 bus to Watertown. Or you can take the 71 bus directly. Thus 1+70=71.

Fun burger toppings

Fried egg, mashed potato, avocado or guacamole.

Privacy audit and seal

Let there be a third-party auditing service that websites can earn a seal of approval saying they do not collect user-identifiable information.

Window screen

The fine wires that make up window screens are circular in cross section (cylindrical). Can air flow through the screen be improved with a more streamlined cross section?

Parallel find and xargs

parallel "find -exec" and xargs that limits the number of threads.

Weakness of Fourmilab javascrypt

256-bit key is generated from a passphrase by taking the even-position letters, hashing to create a 128-bit result, taking the odd-position letters, hashing to create a 128-bit result, and concatenating the hashes. Two passphrases which are the same on (say) the even positions will agree on the first 128 of the 256 bits of key, and then on the average 64 of the latter 128 for a total of 192/256 bits, which is horrible. The right way to do it is to use a real 256-bit hash function (SHA-512) ideally iterated a few hundred times to foil brute-force password cracking.

Bayesian networks

Plain Bayesian networks are practically small. Otherwise you can never get enough data to learn or test them. Since the inference problem and the learning problem are both practically solved for small networks, perhaps the largest remaining problem is a UI one, that is presenting the tool as something the user believes to be useful, and it actually is.

Small temporal networks are also solved.

N-grams with holes

Must avoid ambiguity.

Words

Words that are nearly spelled the same but are very different: bikini and biking, uniformed and uninformed, winch wench wrench, predicted predicated, plaque plague

Pronunciation difference, in particular vowels.

gpg read-only

gpg shouldn't fatal abort if it can't read/write/create secring.gpg if all we are going to do is encrypt from pubring.gpg