[EM] Schulze's method is BeatpathWinner

Markus Schulze markus.schulze at alumni.tu-berlin.de
Fri Apr 1 00:12:51 PST 2005


Dear Mike,

you wrote (1 April 2005):
> SSD isn't a special case of BeatpathWinner. SSD
> and BeatpathWinner are two dilfferent methods that
> can give two different outcomes wilth the same
> ballot-set, as in the example that I posted yesterday.
> In an example such as that, BeatpathWinner and SSD
> give different results. There isn't come version
> of BeatpathWinner that is SSD.

But in your example you argue that BeatpathWinner
is indifferent between A and D while SSD chooses D.
Therefore, your example doesn't demonstrate that
"SSD isn't a special case of BeatpathWinner".
To demonstrate that "SSD isn't a special case of
BeatpathWinner" you would have to post an example
where SSD chooses a candidate who isn't a potential
BeatpathWinner winner. But this is not possible
because also SSD has this property (which makes
SSD a tie-breaking strategy for the Schulze method):

   If p(z)[A,B] > p(z)[B,A], then candidate B must
   be elected with zero probability.

Markus Schulze



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