[EM] Correction on BPW cyclebreaker (Stensholt's method)

[Kevin Venzke]

Hi,

The BPW (= "Beats Plurality Winner") method is a cyclebreaker proposed
by Eivind Stensholt that he found to be resistant to burial. When there
is a cycle among three candidates, you elect the one who defeats the
first preference winner. (It's unknown how to define the method for 
more than three.) I coded it (incorrectly) and probably commented that 
I wasn't impressed.

However, having fixed the error, I feel the need to say I was wrong and
that it is quite good at what it does. I tried it in three scenarios
(aspectral, 1D, and center-heavy-nomination 1D) and in all three it
either had the lowest burial rate for a Condorcet method, or (in one 
case) was beaten slightly by Condorcet//King of the Hill.

The compromise and truncation incentives are pretty mediocre (i.e. 
highish) though. There's also a little pushover incentive. (I didn't 
allow compression due to the nature of the method.)


I'm planning to compile some stats from my sim to put in an Excel file
that people can download and look through on their own... That way
I won't have to type everything up and people can sort as they wish
and such.

There is probably also a need to distribute method source code so that
if I have implemented a method incorrectly (as in this case) it may be
spotted someday...

Kevin Venzke