From: James Propp <jpropp@cs.uml.edu>

Steve Witham wrote:

...

Here's a comic with an interesting random-walk problem:

http://www.xkcd.com/356/

The problem in question was

...

On an infinite square lattice with equal unit resistances along each edge, find the resistance between two nodes at a knight's move from one other.

Nobody's described the precise connection with random walks,

People might have thought it had to do with absent-minded mathematicians crossing the street in the comic. I didn't think of that. Might be fun to work into the joke or the problem.

By the way, what Fred Lunnon calls "admittence", namely the reciprocal of resistance, is something I always thought was called "conductance". Is this ones of those transatlantic terminological differences?

Ask nice and Google replies in two first hits:

[Admittence]

Did you mean: admittance?

[yes]

Admittance - Wikipedia, the free encyclopedia In electrical engineering, the admittance (Y) is the inverse of the impedance (Z).

Impedance is complex whereas resistance is real. You're right, conductance is the inverse of plain resistance. Wouldn't it be faster to set some initial weights (absolute voltages) over the grid and just loop redistributing weights among neighbors while always resetting the two endpoints to 1 and 0 (resp.)? (And then run the result through Plouffe's Inverter for an added touch of magic before turning in your answer.) --Steve It's very dark and after 23:59.